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    PESTICIDE RESIDUES IN FOOD - 1984


    Sponsored jointly by FAO and WHO






    EVALUATIONS 1984




    The monographs



    Data and recommendations of the joint meeting
    of the FAO Panel of Experts on Pesticide Residues
    in Food and the Environment and the
    WHO Expert Group on Pesticide Residues
    Rome, 24 September - 3 October 1984

    Food and Agriculture Organization of the United Nations
    Rome 1985

    DIMETHOATE

    Explanation

         Dimethoate was evaluated by the Joint Meetings held in 1965 and
    1966; a complete revision was written in 1967, with addenda in 1970
    and 1977. 1/ At the 1973 Joint Meeting the related compound
    formothion was reviewed. In 1978 the Joint Meeting studied dimethoate,
    omethoate and formothion together and expressed the view that residues
    arising from the use of dimethoate should be determined and expressed
    as the sum of dimethoate and omethoate, while residues arising from
    the use of omethoate should be determined and expressed as omethoate.

         The CCPR at its Twelfth Session (ALINORM 81/24, para 64)
    requested the JMPR to consider separating the recommendations for
    these compounds in view of the wide difference between their ADIs.
    Efforts were therefore made to determine whether there was an adequate
    data base upon which to recommend separate MRLs for the two compounds.
    In response to a request to governments, a small amount of information
    was received from Australia, Canada, Denmark, The Netherlands, New
    Zealand, Portugal, Sweden and the UK. An extensive search of open
    scientific literature was made and the many manufacturers of technical
    dimethoate and many of the major formulators of dimethoate pesticides
    were contacted with variable response. A spokesman for the task force
    set up by the dimethoate manufacturers to review, revise and extend
    the available data on dimethoate advised that the required information
    could not be provided before 1987.

         From the information obtained, and reviewed below, it has been
    concluded that there is no basis for proposing separate MRLs for
    dimethoate and omethoate when the latter compound occurs as a
    metabolite of dimethoate and formothion.

    RESIDUES IN FOOD AND THEIR EVALUATION

    USE PATTERN

         Dimethoate was first developed as an insecticide in the mid-
    1950s. Its broad spectrum of effect due to its contact and systemic
    action when applied to both animals and plants has resulted in its
    being adopted for use against a wide variety of pest species on
    virtually every crop except a small number that show phytotoxic
    reaction to some dimethoate formulations. Even in some of these
    situations special formulations have been developed to eliminate or
    reduce the phytotoxicity.


              

    1/  See Annex 2 for FAO and WHO documentation.

         There are currently more than 10 manufacturers of dimethoate and
    there seems little doubt that dimethoate is used for some purpose in
    almost every country. Detailed use patterns were available from about
    10 countries. These indicate a significant degree of similarity in
    application rates and preharvest intervals (Table 1).

    RESIDUES RESULTING FROM SUPERVISED TRIALS

         Most reports of supervised trials present the residues data as
    the sum of dimethoate and omethoate. Only very few reports indicate
    the two values separately. Many of the results are based on the
    determination of total phosphorus measured under controlled
    conditions, and therefore do not provide data on which to judge the
    relative concentrations of parent and metabolite.

         Tables 2 and 3, the latter from a review by Agnihothrudu and
    Mithyantha (1978), summarize the results of some studies which have
    reported the residues as the sum of the two compounds. (Results of
    others are reported in detail by de Pietri-Tonelli et al. (1965).
    Studies which present the values for the concentration of the two
    compounds separately are reported in greater detail in the following
    sections.

    Residues in Fruit

    Apples

         The results of trials by de Pietri-Tonelli and Barontini (1958)
    and Enos and Frear (1964) are quoted by de Pietri-Tonelli et al.
    (1965). The former indicate that the insecticide penetrates from the
    epicarp into the pulp and that 15 days after treatment only a
    negligible amount still remains on the outside of the fruits. After
    penetration, the insecticide gradually diffuses into the pulp and also
    into the core and becomes metabolized at the same time, the half-life
    being approximately 8 days. The trials by Enos and Frear show that the
    initial concentration of the insecticide in the fruits is roughly
    proportional to the concentration of dimethoate applied to the plants.
    They found a lower rate of disappearance (half-life 15-16 days).

         Wit (1972) reported a trial carried out in The Netherlands in
    1971 with two different formulations of dimethoate applied to two
    varieties of apples at the rate of 300 g a.i./1. The apples were
    harvested 1, 2 and 3 weeks after spraying. No omethoate (<0.1 mg/kg)
    was found. The concentration of dimethoate declined from 0.2 mg/kg at
    the time of spraying to 0.14 mg/kg 3 weeks later, with intermediate
    values of 0.1 and 0.3 mg/kg at 1 and 2 weeks.

         Information received from Portugal (1984) gives details of a
    trial in which two groups of 9 apple trees were treated 5 and 7 times
    with dimethoate emulsion (50g/1001) at intervals of 14 days. Analysis
    for dimethoate and omethoate was by GLC (thermionic detector) with a

    limit of determination of 0.01 mg/kg dimethoate and 0.05 mg/kg
    omethoate. The omethoate residues were generally less than 10 percent
    of the total dimethoate and omethoate residue (Table 4).

         The Danish National Food Institute (Denmark, 1984a) provided
    results of trials conducted in 1980 to determine the rate of
    conversion of dimethoate to omethoate in apples sprayed with
    dimethoate for the control of aphids. The treatments were made at the
    highest permitted rate (a) and twice the permitted rate (b). The
    results are given in Table 5.

         A parallel experiment was conducted in which formothion was
    substituted for dimethoate at: (a) the approved rate of application,
    0.5 g/l; and (b) 1.0 g/l. The results are shown in Table 6.

    Apricots

         De Pietri-Tonelli et al. (1965) reported studies carried out
    in 1959 in which apricot fruits were collected from trees sprayed with
    dimethoate at two dosage rates when the pulp of the apricots, still in
    the pre-ripe stage, was beginning to soften. Bioassay indicated, for
    both rates of application, substantially similar rates of
    disappearance of residues having insecticidal activity. The half-life
    was approximately 7 days.

    Black currants

         Chilwell and Beecham (1960), using a method based on the
    determination of phosphorus, showed that the residues in black
    currants 7 and 14 days after application of dimethoate spray (0.5 g/l)
    were 0.1 and 0.4 mg/kg respectively.

    Bananas

         Braithwaite (1963) dipped bananas in dimethoate solution
    (0.3 g/l) for the control of fruit fly. Dimethoate residues in the
    bananas 8 days after dipping were 0.7 mg/kg in the peel and 0.3 mg/kg
    in the pulp. Further studies (Anon. 1969) indicated that the time of
    immersion of the bananas in the dip bath did not significantly alter
    the concentration of dimethoate residues which were between 0.3 and
    0.7 mg/kg in the whole fruit and 0.05 and 0.08 mg/kg in the pulp
    irrespective of whether the time of immersion was 10, 40 or 160
    seconds.

    Cherries

         De Pietri-Tonelli et al. (1965) reported trials carried out
    in 1956 which showed that dimethoate penetrated through the skin of
    sprayed cherries into the pulp within a few hours of treatment. The
    results indicated that the half-life of residues having insecticidal
    activity was about 5 days.


        TABLE 1.  Registered uses of dimethoate

                                                                                                                            

                                                          Rate
                                                                                                        Pre-harvest
    Crop                Country                  g/ha           g/1001         Frequency                interval, days
                                                                                                                            

    Cereals

    barley              Australia                               35
    maize                                                       35
    oats                                                        35
    sorghum                                                     35
    wheat                                                       35
    barley              New Zealand              280-320
    maize                                        280-320
    oats                                         280-320
    rye                                          280-320
    wheat                                        280-320
    sorghum             South Africa             150-200
    wheat                                        200-300
    cereals             UK                       320-680
    corn                USA                      350-500                       3                        14
    sorghum                                      250-500                       3                        28
    soybeans                                     500                                                    21
    wheat                                        250-400                                                14
    barley              Canada                   200-480                                                21
    oats                                         200-480                                                21
    rye                                          200-480                                                21
    wheat                                        200-480                                                21

    Field Crops

    alfalfa             Australia                25-150
    corn fodder                                  25-50
    cotton                                       200
    oilseeds                                     300
    peanuts                                      35
                                                                                                                            

    TABLE 1.  (continued)

                                                                                                                            

                                                          Rate
                                                                                                        Pre-harvest
    Crop                Country                  g/ha           g/1001         Frequency                interval, days
                                                                                                                            

    rapeseed                                     135
    safflower                                    135
    soybeans                                     135
    cotton              (Algeria, Morocco)       200-500
    soybeans            (Tunisia, Senegal)       200-500
    alfalfa             New Zealand              120-200
    chou moellier                                320-400
    rapeseed                                     320-400
    sugarbeet                                    320-400
    cotton              South Africa             300                                                    14
    tobacco                                      300                                                    14
    peanuts                                      200-300                                                14
    fodder best         UK                       84-420                        2                        7
    mangolds                                     84-420                        2                        7
    sugarbeet                                    84-420                        2                        7
    alfalfa             USA                      250-500                       1                        10
    cotton                                       250-500                       2                        14
    safflower                                    250-500                       2                        14
    soybeans                                     500                                                    21
    tobacco                                      250-350                                                21
    alfalfa             Canada                   200-675                                                2, 7, 28
    fababean                                     560                                                    7
    forage crops                                 200-260                                                2
    pastures                                     200-260                                                2
    rapeseed                                     275-300                       1                        30
    sugarbeet                                    560                                                    30
    sweet clover                                 200-260                                                2
                                                                                                                            

    TABLE 1.  (continued)

                                                                                                                            

                                                          Rate
                                                                                                        Pre-harvest
    Crop                Country                  g/ha           g/1001         Frequency                interval, days
                                                                                                                            

    Fruit

    apple               USA                                     60             each 10-14 days          28
    citrus                                       1000-2000      30-60                                   15
    melons                                       500                                                    3
    pears                                                       30-60                                   28
    watermelons                                  250-500                                                3
    apples              Australia                               30-60          7 & 5 weeks              7
                                                                                                        (minimum)
                                                                               pre-harvest
    avocados                                                    30                                      7
    berry fruits                                                30                                      7
    bananas                                                     30             post-harvest             -
    cherries                                                    20                                      7
    citrus                                                      30-60                                   7
    grapes                                                      30                                      7
    mangoes                                                     30                                      7
    melons                                                      30                                      7
    pears                                                       30-60          7 & 5 weeks              7(min.)
                                                                               pre-harvest
    peaches                                                     30             4 & 2 weeks              7(min.)
                                                                               pre-harvest
    plums                                                       30             4 & 2 weeks              7(min.)
                                                                               pre-harvest
    strawberries                                                30                                      7
    apples              France                                  50                                      7
    cherries                                                    30                                      7
    grapes                                                      15                                      7
    melons                                                      30                                      7
    pears                                                       50                                      7
    peaches                                                     30                                      7
                                                                                                                            

    TABLE 1.  (continued)

                                                                                                                            

                                                          Rate
                                                                                                        Pre-harvest
    Crop                Country                  g/ha           g/1001         Frequency                interval, days
                                                                                                                            
    strawberries                                                30                                      7
    pineapples          Algeria, Morocco         200-500
    citrus              Tunisia                  200-500
    bananas                                      20-500
    apples              New Zealand                             20-24
    berry fruit                                                 32
    citrus                                                      32
    pears                                                       20-32
    plums                                                       20-32
    strawberries                                                32
    apples              South Africa                            30-50                                   14
    citrus                                                      20-40                                   14
    grapes                                       2000                                                   28
    pears                                        800-1100       30-50                                   14
    peaches                                      400-1000       40                                      28
    plums                                        720-1680       50                                      28
    pineapples                                                  50                                      14
    strawberries                                                30                                      14
    apples              UK                       336-680                       2                        7
    berry fruit                                                 30             7
    cherries                                     336-680                       2                        7
    pears                                        336-680                       2                        7
    peaches                                                     30                                      7
    plums                                        336-680                       2                        7
    strawberries                                                30             7
    apples              Canada                   1              47-60          3                        7-14
    blueberries                                                 28-40          2                        15
    cherries                                                    25-30          2                        15
    loganberries                                                20-37          2                        -
    peaches                                      800            22             2                        70
    pears                                                       47-60          3                        7-14
    strawberries                                                75             2                        7
                                                                                                                            

    TABLE 1.  (continued)

                                                                                                                            

                                                          Rate
                                                                                                        Pre-harvest
    Crop                Country                  g/ha           g/1001         Frequency                interval, days
                                                                                                                            

    Miscellaneous

    fodder crops        Australia                35-300
    pastures                                     35-300
    olives              France                                  30                                      21
    coffee              (Algeria, Morocco)       200-500
    cocoa               (Senegal, Tunisia)       200-500
    tobacco                                      200-500
    olives                                       200-500
    tobacco             South Africa             320
    hops                UK                                      30             each 3 weeks             7
    alfalfa             USA                      250-500                       1                        10
    cotton                                       250-500                       2                        14
    safflower                                    250-500                       2                        14
    soybeans                                     500                                                    21
    tobacco                                      250-500                       21

    Vegetables

    beans               Australia                320            30             1-3                      7
    beetroot                                     320            30             1-3                      7
    broccoli                                     320            30             1-3                      7
    Brussels sprouts                             320            30             1-3                      7
    carrots                                      320            30             1-3                      7
    cabbage                                      320            30             1-3                      7
    cauliflower         Australia                320            30             1-3                      7
    celery                                       320            30             1-3                      7
    cucurbits                                    320            30             1-3                      7
    leafy vegetables                             320            30             1-3                      7
    lettuce                                      320            30             1-3                      7
    onions                                       320            30             1-3                      7
                                                                                                                            

    TABLE 1.  (continued)

                                                                                                                            

                                                          Rate
                                                                                                        Pre-harvest
    Crop                Country                  g/ha           g/1001         Frequency                interval, days
                                                                                                                            

    parsnips                                     320            30             1-3                      7
    peas                                         320            30             1-3                      7
    peppers                                      320            30             1-3                      7
    potatoes                                     320            30             1-3                      7
    tomatoes                                     320            30             4 & 2 weeks              7(min.)
                                                                               pre-harvest
    tomatoes                                                    30             post-harvest             -
    capsicums                                                   30             post-harvest             -
    artichokes          France                                  30                                      15
    asparagus                                                   50                                      15
    beetroot                                     250            30                                      15
    cabbage                                                     30                                      15
    endive                                                      30                                      15
    lettuce                                                     30                                      15
    peas                                                        30                                      15
    broccoli            New Zealand              400                                                    7
    beetroot                                     320                                                    7
    Brussels sprouts                             400                                                    7
    cabbage                                      400                                                    7
    carrots                                      320                                                    7
    cauliflower                                  400                                                    7
    peas                                         320                                                    7
    potatoes                                     320                                                    7
    sweet corn                                   280                                                    7
    turnips                                      320-400                                                7
    beans               South Africa                            30                                      14
    brassicas                                                   30                                      14
    broccoli                                                    30                                      14
    Brussels sprouts                                            30                                      14
    cabbage                                                     30                                      14
    cauliflower                                                 30                                      14
                                                                                                                            

    TABLE 1.  (continued)

                                                                                                                            

                                                          Rate
                                                                                                        Pre-harvest
    Crop                Country                  g/ha           g/1001         Frequency                interval, days
                                                                                                                            

    cucurbits                                                   30                                      14
    kale                                                        30                                      14
    mustard                                                     30                                      14
    potatoes                                     300                                                    14
    beans               UK                       336                                                    7
    beetroot                                     336                                                    7
    brassicas                                    336                                                    7
    carrots                                      336                                                    7
    peas                                         336                                                    7
    peppers                                                     30                                      7
    potatoes                                     336                           14 day intervals         7
    tomatoes                                                    30                                      7
    turnips                                      336                                                    7
    beans               USA                      250-500                                                1
    broccoli                                     250-500                                                7
    cabbage                                      250-500                                                3
    cauliflower                                  250-500                                                7
    celery                                       500                                                    7
    collards                                     250                                                    14
    endive                                       250                                                    14
    kale                                         250                                                    14
    lettuce                                      250                                                    14
    mustard                                      250                                                    14
    peas                                         250                                                    1
    peppers                                      250-350                                                1
    potatoes                                     250-500                                                1
    spinach                                      250                                                    14
    tomatoes                                     250-500                                                7
    turnips                                      250                                                    14
    beans               Canada                   275-500                       as necessary             7
    broccoli                                     275-500                       "                        4
                                                                                                                            

    TABLE 1.  (continued)

                                                                                                                            

                                                          Rate
                                                                                                        Pre-harvest
    Crop                Country                  g/ha           g/1001         Frequency                interval, days
                                                                                                                            

    Brussels sprouts                             275-500                       "                        4
    cabbage                                      275-500                       "                        4
    cauliflower                                  275-500                       "                        4
    Chinese cabbage                              550                           2                        7
    beetroot                                     275-325                       as necessary             12
    kale                                         275-325                       "                        7
    lettuce                                      275-325                       "                        7
    peas                                         125-200                       "                        3
    peppers                                      325-675                                                3
    potatoes                                     275-675                                                7
    spinach                                      275-325                                                7
    turnip                                       275-325                                                7
    tomatoes                                     275-675                                                7
                                                                                                                            

    Table 2.  Residues reported as sum of dimethoate & omethoate

                                                                                                                                        
                                          Application
                                                                  Residues in mg/kg, at intervals (days) after application
    Crop       Country      Year        rate                                                                                            
                                   no  kg ai/ha  formulation    0         1-2       4         7         10        14      Reference
                                                                                                                                        

    Beans      UK           1958   1   0.1%      -                                                      0.7
    (French)   UK           1958   1   0.1%                                                             0.4
               Egypt        1979   2   0.476     400EC        16.1        13.7      9.8       5.3       1.8       0 (21)  Belal &
                                                                                                                  days    Gomaa 1979

    Brussels   UK           1957   1   0.750                                                  0.7                         Chilwell &
    Sprouts                 1957   1   0.750                                                  0.5                 0.1     Beecham 1960
                            1957   1   0.750                                                                      1.1
                            1958   1   0.12                                                   0.2                 0.2

    Cabbage    UK           1958   1   0.04%                                                  0.1       0.7       0.2     Chilwell
                                                                                                                  (21     & Beecham
                                                                                                                  days)   1960

               UK           1958   1   0.04%                                                  0.3
               UK           1981   1   -                                                                0.2
                                                                                                        0.04      0.02

               India        1977   1   0.25%     -             6.8        3.84                                            Chakraborty &
                                       0.05%                  13.0        6.9                                             Mutatkar 1978
                                       0.1%                   15.4        8.9

               UK           1958   1   0.04%     -                                            1.3                 0.5     Chilwell &
                            1981   1   -                                                                0.1               Beecham 1960

    Carrots    UK           1958   3   1.0                                                                        0.6     Chilwell &
                                                                                                                          Beecham 1960
                                                                                                                                        

    Table 2.  (continued)

                                                                                                                                        
                                          Application
                                                                  Residues in mg/kg, at intervals (days) after application
    Crop       Country      Year        rate                                                                                            
                                   no  kg ai/ha  formulation    0         1-2       4         7         10        14      Reference
                                                                                                                                        

               Netherlands  1965   2   13.0      40EC                     11 weeks
                                                                          0.04
                                                                          0.02
                                                                          0.02
                                                                          0.04

                                   2   13.5      40EC         11 weeks    0.02                                            Greve 1980
                                                              12 weeks    0.03
                                                              14 weeks    0.02

    Beetroot   UK           1958   1                                                          0.09                        Chilwell &
                                                                                                                          Beecham 1960
    Onions     UK           1958   3   1.0                                                                        0.2

    Cucumber   Egypt        1979   2   0.476     900EC        11.8        10.3      6.3       3.2                 0.8     Belal & Gomaa
                                                                                                                          1979

    Tomatoes   Egypt        1979   2   0.476     400EC        27.3                  22.1      10.1                4.7     Belal & Gomaa
                                                                                                                          1979

    Turnips    UK           1958   2   1                                                                          0.4     Chilwell &
                                                                                                                          Beecham 1960
    Kale       UK           1958   1   0.5                                                                        0.3     Chilwell &
                                                                                                                          Beecham 1960
    Peas       UK           1958   1   0.2       -                                            0.3                 0.1     Chilwell &
    (without                1958   1   0.2                                                                                Beecham 1960
    pod)

                                                                                                                                        

    Table 2.  (continued)

                                                                                                                                        
                                          Application
                                                                  Residues in mg/kg, at intervals (days) after application
    Crop       Country      Year        rate                                                                                            
                                   no  kg ai/ha  formulation   10         15        20        25        30                Reference
                                                                                                                                        

    Potatoes   India        1977   5   300       300EC        2.03        1.27      0.69      0.43      0.08              Misra et al.
    (unwashed)                         500       30EC         2.73        1.53      0.87      0.51      0.14              (1981)
                            1977   5   300       300EC        1.87        0.98      0.61      0.21      0.06
                                       500       300EC        2.11        1.07      0.67      0.33      0.09
                                                                                                                                        

    Table 3a.  Residues of dimethoate on crops arising from supervised trials in India.

                                                                                                                                          

                                                                Total                                   Method
    Crop                Variety             Location            Dosage                                  of                  No. of
                                                                used (kg            Formulation         application         application
                                                                a.i/ha)             used
    1                   2                   3                   4                   5                   6                   7
                                                                                                                                          

    Dimethoate;
    Cabbage             Golden              ''                  0.40                30 EC               0.03%               One, 15
                        acre                                                        spray               days before
                        (winter crop)                                               1300 l/ha.          harvest

    Cabbage             Golden              Delhi               0.52                30 EC               0.04%               One, 15
                        acre                                                                            spray at            days before
                                                                                                        1300 l/ha           harvest

                        Spring                                  0.40                ,,                  0.03%               One, 15
                        crop)                                                                           spray               days before
                                                                                                        1300 l/ha.          harvest

                                                                0.52                ,,                  0.04% spray         ,,
                                                                                                        1300 l/ha,

    Cauliflower         Pusa                Delhi               0.42                ''                  0.03% spray         ''
                        Kathki                                                                          1400 l/h.
                        Early
                        crop: Aug-
                        Dec.)

                                                                0.56                ,,                  0.04% spray         ,,
                                                                                                        1400 l/ha.

                                                                                                                                          

    Table 3a.  (continued)

                                                                                                                                          

                                                                Total                                   Method
    Crop                Variety             Location            Dosage                                  of                  No. of
                                                                used (kg            Formulation         application         application
                                                                a.i/ha)             used
    1                   2                   3                   4                   5                   6                   7
                                                                                                                                          

    Cauliflower         Snow                Delhi               0.42                ''                  0.03% spray         ,,
                        ball (Late                                                                      1400 l/ha.
                        crop Oct,
                        Feb.)

                                                                0.56                ''                  0.04% spray         ,,
                                                                                                        1400 l/ha.

    Yellow sarson                           Delhi               0.66                ''                  0.03% spray         Two
                                                                                    2200 l/ha.

                                                                0.50                ,,                  0.0225%             Two
                                                                                    spray
                                                                                    2200 l/ha

    Yellow                                  Delhi               0.88                30 EC               0.04% spray         Two
    sarson

    Brown sarson                            ''                  0.50                ''                  0.0225%             Two
                                                                                                        spray 2200
                                                                                                        l/ha.

    Cabbage                                                     0.225               EC                  Spray

    Cowpea                                  Bhubaneshwar        2.0                 5% Gr.              Soil                Two, at
                                                                                                        application         sowing
                                                                                                                            flower
                                                                                                                            initiation
                                                                                                                                          

    Table 3a.  (continued)

                                                                                                                                          

                                                                Total                                   Method
    Crop                Variety             Location            Dosage                                  of                  No. of
                                                                used (kg            Formulation         application         application
                                                                a.i/ha)             used
    1                   2                   3                   4                   5                   6                   7
                                                                                                                                          

    Grape               Anab-e-             Coimbatore                              30 EC               0.03%               Four, at
                        Shahi                                                                           spray               15 days
                                                                                                                            intervals

    Grape               Muscat              Coimbatore          0.35                ,,                  Spray               ,,

    Guava                                   Ludhiana            30 g/tree           ,,                  0.1% spray          One

    Peach                                   ''                  ''                  ''                  ''                  One

    Coconut             Bangalore                               2.5 g/              ,,                  Stem injection      One
                                                                Tree

                                                                5.0 g/              ,,                  ,,                  One
                                                                tree


    Chillies            Local               Bangalore                               ,,                  0.06%               Once in
                                                                                                        spray               10 days

    Tomato                                  Bangalore           ''                  ,,                  ,,                  3 sprays
                                                                                                                            once in
                                                                                                                            10 days

                                                                                                                                          

    Table 3a.  (continued)

                                                                                                                                          

                                                                Total                                   Method
    Crop                Variety             Location            Dosage                                  of                  No. of
                                                                used (kg            Formulation         application         application
                                                                a.i/ha)             used
    1                   2                   3                   4                   5                   6                   7
                                                                                                                                          

    French              Prochessor          ,,                  ,,                  ,,                  ,,                  Once in
    beans                                                                                                                   10 days

                        Blue crop           ,,                  ,,                  ,,                  ,,                  ,,

                        Ozark               ,,                  ,,                  ,,                  ,,                  ,,

                        Var-60              ,,                  ,,                  ,,                  ,,                  ,,

                        Can yon             ,,                  ,,                  ,,                  ,,                  ,,

                        Royalty             ,,                  ,,                  ,,                  ,,                  ,,
                        purple

                        Silvert             ,,                  ,,                  ,,                  ,,                  ,,

    Groundnut           TMV-7               Palghat                                 ,,                  03% spray           Two

                        TMV-7               Coimbatore                              ,,                  ,,                  ,,
                                                                                                                                           

    Table 3b.

                                                                                                                                                
                                                                          Half      Waiting     Residues    Tolerance    Method
    Crop           Variety          Dissipation rate                      life      period      of          limit        of           Reference
                                    (ppm after days*)                               suggested   harvest     (ppm)        analysis
                                                                          (days)    (days)      (ppm)
    1              2                8                                     9         10          11          12           13           14
                                                                                                                                                

    Dimethoate;
    Cabbage        Golden           Heads: 17.03(0), 4.87(1),             3.95      7.2         0.59        2.0          B            Krishniah
                   acre             3.25(4), 1.64(7), 1.02(10),                                                                       & Rattan
                   (winter crop)    0.59(14)                                                                                          Lal (1973a)

                                    Leaves: 15.11(0), 11.03(1),           4.40                  1.65        ,,           ,,
                                    7.87(4), 4.80(7), 2.63(10),
                                    1.65(14)

                                    Heads: 6.78(0), 5.02(1),                                    0.54        ,,           C            ,,
                                    3.17(4), 1.23(7), 0.82(10),
                                    0.54(14)

                                    Leaves: 15.32(0), 10.84(1),                                 1.39        ,,           ,,           ,,
                                    8.95(4), 4.50(7), 2.82(10),
                                    1.39(14)

    Cabbage        Golden           Head: 9.68(0), 5.87(1),               3.82      8.0         0.79        2.0          B            ,,
                   acre             4.61(4),2.22(7), 1.03(10),
                                    0.79(14)

                                    Leaves: 18.18(0), 15.03(1),           4.35                  2.14        ,,           ,,           ,,
                                    10.42(4), 5.91(7), 3.09(10),
                                    2.14(14)

                                    Head: 9.01(0), 6.99(1), 5.40(4),                            0.67        ,,           C
                                    2.14(7), 1.07(10), 0.67(14)
                                                                                                                                                

    Table 3b. (continued)

                                                                                                                                                
                                                                          Half      Waiting     Residues    Tolerance    Method
    Crop           Variety          Dissipation rate                      life      period      of          limit        of           Reference
                                    (ppm after days*)                               suggested   harvest     (ppm)        analysis
                                                                          (days)    (days)      (ppm)
    1              2                8                                     9         10          11          12           13           14
                                                                                                                                                

                                    Leaves: 17.82(0), 14.03(1),                                 1.82        ,,           ,,
                                    9.55(4), 4.87(7), 2.75(10),
                                    0.22(14)

                   (Spring          Head: 6.99(0), 4.40(1),               2.99      5.7         0.22        ,,           B
                   crop)            3.15(4), 1.80(7), 0.78(10)
                                    0.22(4)

                                    Leaves: 12.86(0), 8.33(1),            3.33                  0.63        ,,           ,,
                                    4.01(4),2.5(7), 1.32(10),
                                    0.63(14)

                                    Heads: 9.02(0), 5.51(1),              3.23      7.0         0.39        ,,           ,,
                                    4.00(4), 1.75(7), 1.04(10),
                                    0.92(14)

                                    Leaves: 15.2(0), 9.07(1),             3.57                  0.92        ,,           ,,
                                    5.77(4), 2.97(7), 1.71(10),
                                    0.33(14)

    Cauliflower    Pusa             Curds: 6.37(0), 4.85(1),              3.38                  0.33        ,,           ,,
                   Kathki           3.28(4), 1.57(7),0.97(10),
                   (Early           0.33(14)
                   crop: Aug-
                   Dec.)            Leaves: 12.61(0), 9.50(1),            3.82      5.7         0.95        ,,           ,,
                                    5.18(4), 2.63(7), 1.7(10),
                                    0.95(14)

                                                                                                                                                

    Table 3b. (continued)

                                                                                                                                                
                                                                          Half      Waiting     Residues    Tolerance    Method
    Crop           Variety          Dissipation rate                      life      period      of          limit        of           Reference
                                    (ppm after days*)                               suggested   harvest     (ppm)        analysis
                                                                          (days)    (days)      (ppm)
    1              2                8                                     9         10          11          12           13           14
                                                                                                                                                

                                    Curds: 6.90(0), 4.46(1),                                    0.44        ,,           C
                                    2.79(4), 1.78(7), 0.96(10),
                                    0.44(14)

                                    Leaves: 13.54(0), 9.58(1),                                  1.21        ,,           ,,
                                    5.28(4), 1.93(7), 1.51(10),
                                    1.21(14)

                                    Curd: 8.80(0), 5.29(1),               3.23      6.9         0.35        ,,           B
                                    3.59(4), 1.69(7), 1.12(10),
                                    0.35(14)

                                    Leaves: 14.26(0), 10.0(1),            4.02                  1.45        ,,           ,,
                                    6.70(4), 3.09(7), 1.67(10),
                                    1.45(14)


                                    Curd: 8.71(0), 5.65(1), 3.11(4),                            0.49        ,,           C
                                    1.55(7), 0.86(10), 0.49(14)

                                    Leaves: 14.75(0), 9.72(1),                                  1.15        ,,           ,,
                                    5.70(4), 2.28(7), 1.32(10),
                                    1.15(14)

    Cauliflower    Snow             Curd: 6.71(0), 5.66(1),               4.30      7.5         0.81        ,,           B
                   ball(Late        2.86(4), 1.70(7), 0.94(10)
                   crop Oct.        0.81(14)
                   Feb.)

                                                                                                                                                

    Table 3b. (continued)

                                                                                                                                                
                                                                          Half      Waiting     Residues    Tolerance    Method
    Crop           Variety          Dissipation rate                      life      period      of          limit        of           Reference
                                    (ppm after days*)                               suggested   harvest     (ppm)        analysis
                                                                          (days)    (days)      (ppm)
    1              2                8                                     9         10          11          12           13           14
                                                                                                                                                

                                    Leaves: 11.14(0), 8.33(1),            4.33                  1.29        ,,           ''
                                    5.09(4), 2.20(7), 1.84(10),
                                    1.29(14)

                                    Curd: 6.48(0), 5.20(1), 2.75(4).                            0.74        ,,           C
                                    1.27(7), 0.87(10), 0.74(14)

                                    Leaves: 11.67(0), 8.64(1),                                  1.23        ,,           C
                                    5.69(4), 2.31(7), 1.60(10),
                                    1.23(14)

                                    Curd: 8.75(0),5.79(1),                4.13      8.8         0.92        ''           B
                                    3.04(4), 1.68(7), 0.97(10),
                                    0.92(14)

                                    Leaves: 13.09(0), 8.97(1)             4.36                  1.51        ,,           ,,
                                    5.91(4), 2.93(7), 1.67(10),
                                    1.51(14)

                                    Curd: 8.21(0), 5.64(1), 2.91(4),                            0.81        ,,           C
                                    1.81(7), 1.09(10), 0.81(14)

                                    Leaves: 13.60(0); 9.15(1),            -                     1.27        ,,           ,,
                                    5.80(4), 3.04(7), 1.82(10),
                                    1.27(14)

                                                                                                                                                

    Table 3b. (continued)

                                                                                                                                                
                                                                          Half      Waiting     Residues    Tolerance    Method
    Crop           Variety          Dissipation rate                      life      period      of          limit        of           Reference
                                    (ppm after days*)                               suggested   harvest     (ppm)        analysis
                                                                          (days)    (days)      (ppm)
    1              2                8                                     9         10          11          12           13           14
                                                                                                                                                

    Yellow sarson                   Leaves: 8.27(0), 6.38(1),             3.46      8.0         Seed: ND    ,,           B            Krishniah &
                                    2.25(3), 1.66(5), 1.01(7),                                                                        Rattan
                                    0.60(10), 0.56(14)                                                                                Lal (1973b)

                                    Leaves: 9.15(0), 6.45(1),2.88(3)                                        ,,           C            ,,
                                    1.78(5), 0.77(7),
                                    0.70(10), 0.61(14)

                                    Green pods: 3.93(0), 2.40(4),         4.85      5.0                     ,,           B            ,,
                                    1.58(7), 0.62(14), 0.19(21)

                                    Green pods: 4.07(0), 2.24(4),                                           ,,           C
                                    1.41(7), 0.54(14), ND(21)

    Yellow                          Green pods: 6.29(0), 3.71(4),         5.1       8.4         Seed:ND     2.0          B
    sarson                          2.55(7), 0.93(10), 0.37(21)

                                    Green pods: 5.69(0), 2.37(4),                                                        C
                                    2.31(7), 0.83(14), ND(21)

    Brown sarson                    Green pods: 3.90(0),2.14(4),          5.2       5.0         Seed:ND     ,,           B            Krishniah
                                    1.21(7), 0.40(14), 0.10(21)                                                                       & Rattan

                                    Green pods: 3.91(0), 1.86(4),                                           ,,           C            Lal (19736)
                                    1.08(7), 0.42(14), ND(21)

                                                                                                                                                

    Table 3b. (continued)

                                                                                                                                                
                                                                          Half      Waiting     Residues    Tolerance    Method
    Crop           Variety          Dissipation rate                      life      period      of          limit        of           Reference
                                    (ppm after days*)                               suggested   harvest     (ppm)        analysis
                                                                          (days)    (days)      (ppm)
    1              2                8                                     9         10          11          12           13           14
                                                                                                                                                

                                    Green pods: 6.45(0), 3.05(4),         5.9       10.0        Seed:ND     ,,           B
                                    2.60(7), 1.37(14), 0.46(21)

                                    Green pods: 6.30(0),3.33(4),                                            ,,           C            ,,
                                    2.72(7), 1.24(14), 0.49(21)

    Cabbage                                                                         3-7         0.47-1.92   ,,                        Vevai
                                                                                                                                      (1974a)

    Cowpea                          Leaves: 1.437(10), 0.920(20)                                            ,,           ,,           Sathpathy
                                    0.575(30)                                                                                         et al. (1974)

                                    Fruits: 1.275(10), 0.712(20),
                                    0.300(30)

    Grape          Anab-e-                                                                      0.23-0.32   ,,           B & C        Saivaraj et
                   Shahi                                                                                                              el. (1976b)

    Grape          Muscat           13.5(0), 5.67(1),2.70(2),                       5                       0.75         C            Raju-
                                    1.56(4). 0.12(5), ND(8)                                                                           kkannu et
                                                                                                                                      al. (1977)

    Guava                           2.30(0)                               3.0       1                       2.0          TLC&C        Sohi
                                                                                                                                      (1974)

    Peach                           2.98(0)                               4-5       3                       ,,           ,,           ,,

                                                                                                                                                

    Table 3b. (continued)

                                                                                                                                                
                                                                          Half      Waiting     Residues    Tolerance    Method
    Crop           Variety          Dissipation rate                      life      period      of          limit        of           Reference
                                    (ppm after days*)                               suggested   harvest     (ppm)        analysis
                                                                          (days)    (days)      (ppm)
    1              2                8                                     9         10          11          12           13           14
                                                                                                                                                

    Coconut                         Water: 0.019, 0.003(14),                                                ,,           C            Anon
                                    ND(21)                                                                                            (1977a)

                                    Water: 0.024(7), 0.004(14),                                             ,,           ,,            ,,
                                    ND(21)
                                    Copra: 0.043(14)

    Chillies       Local            Green fruits: 7.89(1), 0.25(15)                                         ,,           ,,           ,,

    Tomato                          1.78(1),0.62(9),0.55(11),                                               ,,           ,,           ,,
                                    0.20(25)

    French         Prochessor       Green fruits: 2.35(2), 1.27(4)
    beans                           0.48(10)

                   Blue crop        Green fruits: 2.35(2), 0.91(4)                                          ,,           ,,           ,,
                                    0.57(10)

                   Ozark            Green fruits: 2.24(2). 1.09(4)                                          ,,           ,,           ,,
                                    0.39(10)

                   Var-60           Green fruits: 2.46(2), 1.00(4)                                          ,,           ,,           ,,
                                    0.65(10)

                   Can yon          Green fruits: 2.56(2), 1.00(4)                                          ,,           ,,           ,,
                                    1.00(10)

                                                                                                                                                

    Table 3b. (continued)

                                                                                                                                                
                                                                          Half      Waiting     Residues    Tolerance    Method
    Crop           Variety          Dissipation rate                      life      period      of          limit        of           Reference
                                    (ppm after days*)                               suggested   harvest     (ppm)        analysis
                                                                          (days)    (days)      (ppm)
    1              2                8                                     9         10          11          12           13           14
                                                                                                                                                

                   Royalty          Green fruits: 2.67(2), 1.09(4)                                          ,,           ,,           ,,
                   purple           0.65(10)

                   Silvert          Green fruits: 2.56(2), 1.27(4)                                          ,,           ,,           ,,
                                    0.65(10)

    Groundnut      TMV-7                                                                        Kernel:0.48 ,,           ,,           ,,
                                                                                                Shell: 1.72 ,,

                   TMV-7                                                                        Kernel:0.55
                                                                                                Shell: 1.94
                                                                                                                                                

    Table 4.  Residues of dimethoate and omethoate in apples resulting from multiple applications of dimethoate
              (Portugal, 1984)

                                                                                                                                               

    Number          Days
    of              between                                             Residues found* (mg/kg)
    applications    last                                                                                                                       
                    application      Field replicate 1         Field replicate 2           Field replicate 3                    Mean
                    and                                                                                                                      
                    harvest        dimethoate   omethoate    dimethoate    omethoate     dimethoate    omethoate      dimethoate    omethoate

    5                  1           1.7          0.12         2.1           0.14          1.7           0.14           1.8           0.13
                       4           1.7          0.10         1.7           0.11          1.2           0.11           1.5           0.11
                       7           1.5          0.10         1.3           0.10          1.2           0.12           1.3           0.11
                      12           1.0          0.09         1.2           0.12          1.1           0.11           1.1           0.11
                      14           0.79         0.09         0.93          0.09          0.86          0.09           0.86          0.09
                      21           0.80         0.11         0.92          0.12          0.79          0.14           0.84          0.12
                      28           0.74         NA           0.72          NA            0.68          NA             0.71

    7                  1           2.7          0.16         2.5           0.14          2.6           0.16           2.6           0.15
                       4           2.3          0.18         2.1           0.18          1.8           0.15           2.1           0.17
                       7           2.1          0.15         1.9           0.16          1.9           0.16           1.9           0.16
                      12           1.8          0.15         1.8           0.14          1.5           0.14           1.7           0.14
                      14           1.7          0.16         1.5           0.14          1.4           0.12           1.5           0.14
                      21           1.6          0.13         1.4           0.14          1.1           0.12           1.4           0.13
                      28           1.3          0.12         1.4           0.11          1.3           0.11           1.3           0.11
                                                                                                                                               

    * Mean of 3 analyses
    NA - not analysed

    Table 5.  Residues resulting from the treatment of apples with dimethoate (Denmark, 1984a)

                                                                                              

    Application details           Treatment (a)                 Treatment (b)
                                                                                              

    Concentration                 0.6 g/l                       1.1 g/l
    Rate of application           400 l/ha                      400 l/ha
    Rate/ha                       1.1 kg/ha                     2.2 kg/ha
    No. of applications           4                             4
    Interval between sprays       7 days                        7 days
    P.H.I.                        10 days                       10 days
                                                                                              

                                                      Residue, mg/kg
    Variety                       Dimethoate     Omethoate      Dimethoate     Omethoate
                                                                                              

    Golden delicious              1.56-1.61      0.17-0.23      0.17-0.23      0.31-0.40
    Cox orange                    1.06-1.61      0.11-0.17      2.32-2.86      0.21-0.29
    Cortland                      1.04-1.09      0.09-0.07      1.48-2.52      0.09-0.14
                                                                                              

    Table 6.  Residues resulting from the treatment of apples with formothion (Denmark, 1984)

                                                                                                          

                           Treatment (a)1                              Treatment (b)1
                                                       Residue, mg/kg
    Variety        Formothion     Dimethoate     Omethoate      Formothion     Dimethoate     Omethoate
                                                                                                          

    Golden
    delicious      n.d2-0.03      0.77-1.73      0.11-0.16      0.05-0.14      1.18-2.0       0.10-0.15

    Cox orange     0.02-0.03      0.86-1.69      0.12-0.17      0.03-0.11      1.34-1.88      0.09-0.12

    Cortland       n.d.-n.d.      1.11-1.35      0.11-0.14      n.d.-n.d.      1.11-1.73      0.05-0.07
                                                                                                          

    1  Details as in Table 4, except application rates were (a) 0.5 g/l and (b) 1.0 g/l.
    2  n.d. - not detected.
    
         In further studies by Santi and de Pietri-Tonelli (1959), the
    concentration of the insecticide in the fruits significantly increased
    in the first days after treatment and then diminished. The increase of
    concentration was attributed to systemic migration from leaves and
    twigs into the fruits.

         Zwick et al. (1975) demonstrated that dimethoate was most
    effective for controlling cherry fruit fly in sweet cherries in
    Oregon, USA. The highest residue of dimethoate was 0.9 mg/kg on the
    day of application. Omethoate residues varied between 0.10 and
    0.37 mg/kg. Details are given in the original publication.

         MacNeil et al. (1975) studied the persistence of dimethoate
    and omethoate in cherries when two sprays of dimethoate were applied
    to both sweet and sour cherries 28 and 14 days prior to harvest. Table
    7 shows the results. The omethoate residue remained relatively
    constant at about 0.2 mg/kg indicating that omethoate is degraded at
    about the same rate as it is formed by metabolism of dimethoate.

         Zwick et al. carried out an extensive study at two sites in
    Oregon to obtain data on the fate of two separate formulations of
    dimethoate applied at 1.35 and 2.0 kg/ha to sweet cherries by 
    air-carrier application. Dimethoate and omethoate were determined
    separately. The analytical data (Zwick et al., 1977) indicated
    that the initial deposit was similar whether wettable powder or
    emulsifiable concentrate was used. The residue concentration declined
    with a half-life of less than 5 days. Omethoate exceeded 0.2 mg/kg in
    only one sample, and was a minor proportion of the total residue until
    about 14 days after treatment or when the total residue had declined
    to about 0.2 mg/kg.

         Since the concentration of omethoate remained relatively constant
    in spite of the steady disappearance of the parent insecticide it
    would appear that omethoate was formed and degraded at about the same
    rate.

    Citrus

         Gunther et al. studied the persistence of residues of
    dimethoate on and in mature Valencia oranges and reported that the
    half-life was approximately 19 days. Their results (Gunther et
    al., 1965) indicate that little or no residue reaches the pulp at
    any stage after application following 1 or 2 treatments.

         De Pietri-Tonelli and Barontini (1960a) sprayed tangerine trees
    with 0.03 percent and 0.06 percent dimethoate when the fruits started
    to change colour from green to yellow and analysed the peel and pulp
    separately. The results (de Pietri-Tonelli et al., 1965) show that
    most of the insecticide was localized in the peel where it was
    degraded. Irrespective of the dosage, the half-life of the deposit in
    the peel was 13-14 days. In the pulp of the fruits sprayed with the
    lower concentration the residues were below the limit of determination

    (0.1 mg/kg), whereas in the pulp of those treated with the higher
    concentration, residues of 0.18 mg/kg were found after 10 days. These
    decreased with a half-life of over 45 days.

         De Pietri-Tonelli et al. (1965) recorded that when dimethoate
    (1g/l) was applied to grapefruit for the control of certain scales
    (Wood, 1964) the residue was principally in the peel and diminished
    very slowly. In the pulp, the residue level remained below 1 mg/kg but
    the concentration steadily rose until the fruits became ripe 90 days
    after spraying. It is evident, therefore, that if the total residue
    determined in the pulp was dimethoate, the behaviour of the
    insecticide in grapefruit differs significantly from that observed in
    tangerines.

         Woodham et al (1974a) determined dimethoate and omethoate on
    and in citrus leaves by a GC/FPD procedure following treatment of the
    trees with: (1) an ultra-low volume (ULV) concentrate; and (2) a high
    volume (HV) spray, both applied by helicopter at the rate of 1 kg/ha.
    The ULV treatment produced higher initial residues, probably owing to
    excessive run-off of the aqueous HV spray solution from the waxy leaf
    surfaces. Only 1-5 percent of the deposit from both treatments was
    converted into omethoate in the first 2 days and thereafter the
    concentration of dimethoate decreased rapidly with a gradual decrease
    in the concentration of omethoate. After 7 days, dimethoate residues
    were 0.3-3.4 mg (UV) and 0.05-1 mg/kg (HV), with corresponding
    omethoate levels of 0.15-0.9 mg/kg and <0.05-0.17 mg/kg. The
    omethoate had disappeared entirely by 14 days and dimethoate residues
    were almost all below 0.1 mg/kg.

         The same authors studied the concentration and fate of dimethoate
    and omethoate in the leaves, skin and pulp of grapefruit treated with
    dimethoate wettable powder applied by spray gun at a concentration of
    0.625 g a.i./l with and without surfactant. The results (Woodham et
    al., 1974b) showed that the residue was substantially all in the
    peel and mainly (>90%) dimethoate. Two days following treatment, mean
    residues of 6.28 mg/kg of dimethoate and 0.23 mg/kg of omethoate were
    detected on and in the peels. After 14 days, these residues had
    decreased to 3.13 and 0.16 mg/kg respectively. Residues of dimethoate
    in the pulp of the fruit were 0.09, 0.12 and 0.03 mg/kg after 2, 7 and
    14 days respectively. No omethoate was detectable in any of the pulp
    samples.

         Van Dyk (1974) using a complex mathematical approach to the study
    of the persistence of some pesticides in South African citrus
    concluded that the apparent persistence of dimethoate in growing fruit
    was not influenced by climatic conditions. This seeming anomaly may be
    explained by the predominant influence of growth dilution on the
    concentration of dimethoate on and in citrus fruits, which may mask
    the effects of smaller influences.

    Table 7.  Rate of degradation of dimethoate and omethoate on cherries

                                                                     

                                Residue, mg/kg
                                                                     
                   Sweet cherries              Sour cherries
                                                                     
    Day       Dimethoate    Omethoate      Dimethoate   Omethoate
                                                                     

    0a        0.24          0.14           0.48         0.22
    1         2.30          0.24           2.76         0.23
    2         1.65          0.21           1.91         0.23
    4         1.24          0.23           1.56         0.31
    7         0.89          0.21           0.80         0.28
    14        0.53          0.19           0.38         0.33
                                                                     

    a  Residues measured at day 0 are those remaining frcm first cover
       spray applied 14 days earlier on samples taken prior to the 
       application of the second cover spray.

         Iwata et al (1979) studied the fate of dimethoate applied to
    citrus trees in California. They reported that the edible portion
    (pulp) of fruit sampled about 60 days after application contained no
    analytically significant residues.

         Neubauer et al (1982) studied the accumulation of residues in
    leaves and mature fruits of citrus when dimethoate was applied to the
    soil in a citrus grove. The residue levels in the fruits were much
    lower than in the leaves.

    Grapes

         Enos and Frear (1964) used a colorimetric method to determine
    dimethoate residues in grapes sprayed at the rate of 500 g/ha. Their
    data (de Pietri-Tonelli et al., 1965) indicate that the
    application of the insecticide at this dosage produced high residues
    (6.8 mg/kg) 1 day after treatment which declined progressively at a
    rate corresponding to a half-life of 8-9 days. Analytically
    significant residues persisted for more than 50 days.

         Rajukkannu et al (1977) working in India and using a
    colorimetric method of analysis reported similarly high residues in
    muscat grapes immediately after spraying but these declined to
    0.12 mg/kg after 5 days and to undetectable levels by 8 days.

         Steller and Pasarella (1972) collected grapes from a study in
    which three applications of dimethoate were made at a rate of
    2.5 kg/ha. The samples were analysed 0, 3, 7, 14, 21 and 28 days after
    the final application. The level of dimethoate decreased from 4 mg/kg
    at 0 days to 2.5 mg/kg at 3 days and 0.6 mg/kg at 14 days. This latter
    value remained fairly constant at 0.5 mg/kg in samples collected 21
    and 28 days after application. The omethoate level increased slightly
    from 0.2 mg/kg at 0 days to 0.28 mg/kg at 3 days and then decreased
    gradually to 0.15 mg/kg at 28 days.

         Steller and Brand studied the metabolism of dimethoate in grapes.
    They too found that the initial deposit of dimethoate was converted to
    a small degree into omethoate, the concentration of which remained
    relatively constant at about 0.2-0.4 mg/kg over the 35 days of the
    trial. The concentration of the initial deposit of dimethoate
    (7-18 mg/kg) had decreased to about 1-2 mg/kg by 21 days and to
    0.2-0.5 mg/kg by 35 days (Steller and Brand, 1974).

    Peaches

         De Pietri-Tonelli et al. (1959) conducted bioassays to
    establish the rate of disappearance of dimethoate from peaches and to
    investigate its relationship with the date of treatment of different
    peach varieties, with the concentration of the insecticide applied to
    the plants and with the growth of fruit. The concentration of residues
    having insecticidal activity decreased at higher rates in the
    varieties which were treated in June than in those sprayed in
    September or October. The half-life values were about 4 to 5 days for

    the former and about 9 to 12 days for the latter. It was demonstrated
    that the weight of the pulp of the fruits increases more rapidly in
    the early than in the late varieties.

         Santi (1961) sprayed peach trees with P32-labelled dimethoate at
    a concentration higher than that recommended for the control of fruit
    flies. The results (de Pietri-Tonelli et al., 1965) indicate that
    the concentration of dimethoate in peaches treated in July diminished
    with a half-life of 7 to 8 days. Omethoate reached a maximum of
    0.07 mg/kg after about 10 days, when the dimethoate residue was
    0.83 mg/kg.

         Information received from Portugal (1984) records details of a
    trial in which two groups of nine peach trees were sprayed with
    dimethoate emulsion (40 g/1001) 2 and 3 times respectively at
    intervals of 16 days in the summer of 1982 (average air temperature
    25°C). Samples were collected from each field 1, 4, 7, 11, 14 and 21
    days after the last application. Dimethoate and omethoate residues
    were determined on three replicate samples of whole fruit (stones
    removed but included in weight of sample) by a GLC (thermionic
    detector) method with a limit of determination of 0.01 mg/kg
    dimethoate and 0.05 mg/kg omethoate. The omethoate residues were
    always less than 10 percent of the sum of dimethoate and omethoate
    residues (see Table 8).

    Plums

         Wit (1972) carried out trials in two districts of The Netherlands
    on two varieties of plums treated at two different times with two
    dimethoate formulations. Analysis for the sum of dimethoate and
    omethoate showed residues immediately after application of 0.3 mg/kg.
    The residues declined rapidly so that most samples showed less than
    0.01 mg/kg 1 and 2 weeks after application.

    Strawberries

         Data from Canada quoted in the 1977 evaluation indicated the need
    for an MRL of 1 mg/kg.

         Ahmad et al (1984) conducted an extensive trial with
    3 varieties of strawberries treated with dimethoate spray at 3
    concentrations applied on 4 occasions at 7-day intervals, to determine
    whether a withholding period shorter than 7 days could be approved
    without risk of violating the Australian MRL of 2 mg/kg for the sum of
    dimethoate and omethoate. Samples were analysed by a procedure which
    gave an average recovery of 95 percent for both dimethoate and
    omethoate, with a limit of determination of 0.05 mg/kg.

         As shown in Tables 9-11, the dimethoate residue was independent
    of the strawberry variety but roughly proportional to the
    concentration of dimethoate in the spray. No omethoate was detected in
    any sample. On the strength of these data it was accepted that when


        Table 8.  Residues of dimethoate and omethoate in peaches resulting from multiple applications with dimethoate

                                                                                                                                               

    Number         Days
    of             between                     Residues* (mg/kg)
    applications   last                                                                                                                   
                   application       Field replicate 1          Field replicate 2           Field replicate 3                Mean
                   and                                                                                                                    
                   harvest        dimethoate   omethoate     dimethoate   omethoate      dimethoate   omethoate     dimethoate   omethoate
                                                                                                                                               

    2                 1           1.8          0.09          2.2          0.09           1.7          0.07          1.9          0.08
                      4           1.3          0.09          1.4          0.08           1.5          0.05          1.4          0.07
                      7           0.89         0.08          1.0          0.09           0.98         0.09          0.95         0.09
                     11           0.54         0.07          0.66         0.05           1.0          0.08          0.73         0.07
                     14           0.54         0.08          0.64         0.08           0.73         0 06          0.64         0.07
                     21           0.52         NA            0.61         NA             0.57         NA            0.57

                      1           2.4          0.19          2.5          0.20           2.0          0.18          2.3          0.19
                      4           1.6          0.15          1.8          0.17           1.5          0.15          1.6          0.16
                      7           1.3          0.16          1.5          0.17           1.4          0.15          1.4          0.16
                     11           1.2          0.14          1.2          0.14           1.0          0.15          1.1          0.14
                     14           1.1          NA            1.2          NA             0.83         NA            1.0
                     21           0.9          NA            0.7          NA             0.86         NA            0.82
                                                                                                                                               

    * Mean values of 3 analyses, total weight basis
    NA - not analysed

    Table 9.   Mean dimethoate residues in strawberry fruit following spray application at 200 mg/1.

                                                                                                          

    Number of                                Strawberry Variety
    days after         Torrey                 Tioga                 Naratoga                Mean
    4th spray                                                                                        
                   R*         SE+         R         SE          R           SE         R           SE
                                                                                                          

    0              2.69       .17         3.33      .21         2.40        .20        2.81        .27
    1              1.98       .46         2.17      .48         1.78        .20        1.98        .11
    2              1.51       .10         1.37      .24         1.83        .26        1.57        .14
    3              0.99       .03         1.03      .24         1.28        .20        1.10        .09
    4              0.54       .10         0.81      .33         0.95        .05        0.77        .12
    7              0.36       .08         0.75      .18         0.82        .05        0.64        .14
    14             0.46       .23         0.11      .02         0.33        .10        0.30        .10
    21             0.34       .08         0.06      .01         0.14        .01        0.18        .08
                                                                                                          


    Table 10.  Mean dimethoate residues in strawberry fruit following spray application at 300 mg/l.

                                                                                                          

    0              3.23       .30         3.91      .09         3.80        .81        3.65        .21
    1              2.18       .44         3.25      .20         2.25        .12        2.56        .34
    2              1.45       .24         2.09      .19         2.17        .07        1.90        .23
    3              0.93       .13         1.42      .12         1.78        .12        1.38        .25
    4              0.54       .12         1.35      .22         1.31        .21        1.07        .26
    7              0.37       .49         0.82      .07         0.88        .11        0.69        .16
    14             0.15       .02         0.30      .10         0.30        .10        0.25        .05
    21             0.29       .02         0.29      .18         0.31        .03        0.30        .007
                                                                                                          

    Table 11.  Mean dimethoate residues in strawberry fruit following spray application at 500 mg/l.

                                                                                                          

    0              7.25       .45         6.59      .41         5.06        .48        6.30        .65
    1              5.95       .39         4.91      .39         4.67        .43        5.18        .39
    2              3.25       .67         3.75      .74         3.74        .80        3.58        .16
    3              1.95       .12         2.73      .21         2.39        .27        2.36        .23
    4              1.68       .17         1.45      .33         1.99        .19        1.71        .16
    7              1.18       .08         0.78      .09         1.00        .21        0.99        .12
    14             0.57       .14         0.57      .06         0.44        .11        0.53        .04
    21             0.47       .10         0.33      .14         0.33        .02        0.38        .05
                                                                                                          


    R* = Dimethoate residue (mg/kg)
    +SE = ± Standard Error
    
    dimethoate spray of concentration 300 mg/l is applied on a 7-day
    schedule the ripe fruit can be picked 3 days after application without
    risking violation of the maximum residue limit of 2 mg/kg.

    Olives

         An extensive review of the early history of the use of dimethoate
    for the control of olive fly was published by Alessandrini (1962). By
    the mid 1950's dimethoate was widely used in most of the Mediterranean
    countries and extensive monitoring by the Italian Ministry of
    Agriculture during the years 1957, 1958 and 1959 showed that
    commercial olive oil contained less than 0.1 mg/kg of dimethoate, the
    limit of determination then available. A number of factors contribute
    to keeping the level of residues low:

    1.   Dimethoate is applied to the crop well before harvest;

    2.   the deposit is degraded relatively quickly;

    3.   the residue is polar, particularly the omethoate metabolite;

    4.   the processing of olives into oil and the washing of the oil with
         water as the first step in its refining results in the removal of
         virtually all of the omethoate and much of the remaining
         dimethoate.

         Table olives are picked not less than one month after the last
    treatment with dimethoate and therefore the residues in the
    unprocessed olives are relatively small. Subsequent processing of the
    raw olives removes more than 90 percent of the residues originally
    present.

         Bazzi et al (1960) sprayed olive trees with dimethoate
    (0.6 g/l) at various times between August and November. Details are
    given by de Pietri-Tonelli et al. (1965). Initial half-life
    periods increased progressively from 3-4 days in August to about 23
    days in November.

         The distribution of dimethoate and of its phosphorus-containing
    metabolites in olive fruits was studied by de Pietri-Tonelli and
    Barontini (1961) using radio-labelled dimethoate. They showed that the
    insecticide penetrated into the olives through the skin and
    systemically through the stem.

         Ramos and Costa (1962) found dimethoate residues of 0.7, 0.3 and
    0.5 mg/kg respectively 1, 15 and 30 days after treatment.

         Further studies on olives for oil were undertaken by Santi and
    Giacomelli (1962) who sprayed olive trees with P32-labelled dimethoate
    in July, September and October. The results (de Pietri-Tonelli et
    al., 1965) indicate that the concentration of dimethoate in the
    olives progressively diminishes, the amount of P=O derivative rises to

    a maximum and then decreases, the concentration of water-solubles
    increases and the chloroform- and water-insolubles begin to decline
    about 5 weeks after treatment. The concentration of the insecticide in
    the fruit was directly proportional to the concentration of the
    insecticide spray, the number of applications and the variety of
    olives which influences the surface to weight ratio.

         Irrespective of the rate of application or the time of the year
    when the spray was applied, omethoate represented less than 10 percent
    of the total residue 4 to 5 days after treatment. Although the
    concentration of omethoate did not increase significantly thereafter
    the rapid decline of the total residue meant that by the 15th-18th day
    the omethoate portion represented 50 percent and thereafter the
    proportion increased until by the 45th day the omethoate represented
    80 percent of the total residue (0.7 mg/kg).

         The same authors determined residues in fresh eating olives.
    Bearing in mind the lower ratio of surface-to-mass of eating olive
    varieties and the influence of this factor on the initial
    concentration of the insecticide in the fruits, the results (de
    Pietri-Tonelli et al., 1965) can be considered very similar to
    those obtained in the olives for oil.

         Albi and Rejano (1982) reported residues of dimethoate in fresh
    olives of 0.93-0.95 mg/kg 24 hours after application.

         Ferriera and Tainha (1983) carried out residue dissipation
    studies with a range of organophosphorus insecticides on olives in
    Portugal with a view to checking the preharvest intervals established
    for olives. Following the treatment of olive trees with dimethoate
    spray (0.6 g a.i./l) the authors reported mean residues of 5.3, 3.1,
    1.5, 0.78, 0.41, 0.28 and 0.03 mg/kg after 1, 7, 14, 21, 28, 35, and
    41 days, respectively.

    Residues in Vegetables

         Chilwell and Beecham (1960) made an extensive study of the
    residues found in many British and overseas crops 1-3 weeks after
    spraying with dimethoate. This included a wide variety of vegetables.
    Some results are included in Table 2. De Pietri-Tonelli et al.
    (1965) reviewed much of the available information published to that
    date on beans, carrots, potatoes and sugar beets.

    Beans

         Van Middelem and Waites (1964) analysed snap beans treated with
    dimethoate at 3 dosage rates and compared colorimetric and gas-
    chromatographic methods of analysis. The results (de Pietri-Tonelli
    et al., 1965) showed excellent agreement between the two
    procedures and demonstrated that dimethoate residues were proportional
    to the dosage applied to the plants and disappeared at the same rate,
    with a half-life of about six days, from all three rates of
    application.

         Results obtained by Belal and Gomaa (1979) are quoted in Table 2.
    They calculated the residue half-life to be 4.3 days. The analytical
    method used (Giang and Schecter, 1963) should also have determined any
    omethoate that was present. These residue levels are much higher than
    those reported by other workers.

    Brussels Sprouts

         Greve and Hogendoorn (1981) reported the results of field trials
    carried out on Brussels sprouts in 3 districts of The Netherlands. The
    crops were sprayed with a dimethoate emulsion (50 g/1001) at the rate
    of 200 g/ha applied three times at approximately 12-day intervals. 1,
    2 and 3 weeks following the last spraying, samples from each field
    were analysed for dimethoate and omethoate residues by methods which
    had a limit of determination of 0.005 and 0.01 mg/kg respectively. The
    highest level of omethoate found was 0.07 mg/kg. The detailed results
    are given in Table 12.

    Carrots

         Stobwasser (1963) sprayed two varieties of carrots with
    dimethoate at two rates. The colorimetric analytical data (de 
    Pietri-Tonelli et al., 1965), showed that the residues in the
    roots were very low a few weeks after the last treatment and slowly
    diminished thereafter so that they were below the limit of
    determination
    (0.03 mg/kg) about 200 days after the last application. The total
    residues are likely to be higher than indicated because the analytical
    method used would not detect omethoate.

    Chicory

         Ten Broeke and Dornseiffen (197.3) studied the uptake and
    degradation of dimethoate applied to Witloof chicory in forcing beds
    when the shoots first began to swell. The rate of application was
    equivalent to 0.5 g/m2 applied in the form of a diluted emulsion at
    the rate of 1 1/m2  Two trials were carried at different temperatures
    and four samples from each trial, taken 36 and 50 days after spraying,
    were analysed (see Table 13). The residues of dimethoate and omethoate
    together were generally less than 0.4 mg/kg, the dimethoate and
    omethoate being present in equal proportions.

    Cucumbers

         Greenhouse cucumber plants were treated in three different
    experiments with formulations of either pure or technical dimethoate
    (0.05%) and the residues separated by thin-layer chromatography. The
    amount and nature of the residues did not differ significantly.
    Dimethoate and omethoate were the only residual compounds identified,
    omethoate appearing only in very small quantities. Seven days after
    application, the total residue was less than 0.5 mg/kg in all
    experiments. (Kubel et al., 1966).

    Table 12.  Omethoate and dimethoate residues in Brussels sprouts 
               sprayed with dimethoate 3 times at 10 day intervals 
               starting 4 months after planting. (PHI = interval 
               between last application and harvest)

                                                                     

    Test       PHI      Omethoate (mg/kg)       Dimethoate (mg/kg)
    site       (days)   mean     range          mean     range
                                                                     

    Tinte        7      <0.01     0.01-0.02     0.08     0.005-0.09
                14      <0.01    <0.01          0.02     0.005-0.02
                21      (0.01    <0.01          0.005    0.005-0.005

    Breda        7      <0.01    (0.01          0.05     0.005-0.06
                14      <0.01    <0.01          0.06     0.005-0.10
                21      <0.01     0.01-0.07     0.03     0.005-0.04

    Kirkwyk      7      (0.01    <0.01          0.01     0.005-0.01
                14      (0.01     0.01-0.04     0.01     0.005-0.10
                21       0.01    <0.01          0.005    0.005-0.02
                                                                     

        Table 13.  Dimethoate and Omethoate Residues in Witloof Chicory 
               (ten Broeke and Dornseiffen, 1973a)

                                                                                    

                                  residue, mg/kg, at intervals after application
                                                                                    
                                  Dimethoate                    Omethoate
                                                                                    
                             Test I         Test II        Test I         Test II
                                                                                    

    Cold conditions          36 days        50 days        36 days        50 days

    Untreated                <0.001         <0.001         <0.005         <0.005
                             <0.001         <0.001         <0.005         <0.005

    Treated                   0.11           0.13           0.11           0.13
                              0.15           0.14           0.14           0.18
                              0.12           0.13           0.11           0.14
                              0.11           0.15           0.12           0.14

    Average                   0.12           0.14           0.12           0.15

    Average corrected
    for recovery              0.14           0.15           0.15           0.19
                             (0.12-0.17)    (0.14-0.17)    (0.14-0.18)    (0.16-0.23)

    Warm conditions          36 days        50 days        36 days        50 days

    Untreated                <0.001         <0.001          0.07+         <0.005
                             <0.001          0.007          0.03+          0.02

    Treated                   0.14           0.12           0.24           0.17
                              0.18           0.10           0.23           0.12
                              0.17           0.11           0.20           0.16
                              0.14           0.22           0.19           0.20

    Average                   0.16           0.14           0.21           0.16
    Corrected for control                    0.16

    Average corrected for
    recovery                  0.18           0.15           0.20           0.20
                             (0.16-0.20)    (0.11-0.24)    (0.18-0.24)    (0.15-0.25)
                                                                                    

    + Contamination by solvent (ethyl acetate)
    
    Tomatoes

         As part of a programme of investigations into methods for
    controlling fruit fly in a number of fruits and vegetables, Rigney
    (1976) dipped tomatoes which had been artificially infested with
    Queensland fruit fly larvae for 30 seconds in a dilute dimethoate
    emulsion (3 g/l). Half of the tomatoes were rinsed with clean water 30
    minutes after the dipping. Results are shown in Table 14.

         Swaine et al (1984) carried out a similar experiment in which
    the tomatoes were dipped for a period of 3 minutes in a diluted
    dimethoate emulsion containing 0.5 g/l. The results are given in
    Table 15.

    Asparagus

         Szeto et al (1982) studied the level and fate of dimethoate
    residues in asparagus plants after foliar application. They
    applied dimethoate by means of a backpack sprayer at the rate of
    1.12 kg a.i./ha on two occasions approximately 6 weeks apart at 2
    locations. Samples of the above-ground foliage from each treatment
    were analysed for dimethoate and omethoate by GLC-AFID. The results
    (Table 16) show that dimethoate is oxidized to omethoate in the
    asparagus foliage and that the residues disappear rapidly. No residue
    was detected (<0.002 mg/kg) in samples of the marketable spears
    harvested in the spring of the following year (9 months after
    treatment).

    Cereals

         Lee and Westcott (1981) carried out field experiments on wheat
    plants sown at three different dates to ensure that at the time of
    spraying with dimethoate (420 g/ha) the plants were at three stages of
    development: the boot stage, second node visible, and tillering.
    Samples were collected immediately after application and at several
    intervals over the next three weeks. The dimethoate and omethoate
    residues are recorded in Table 16a. These data indicate that the
    conversion to omethoate and the subsequent degradation of the
    metabolite is slightly greater in young than in mature plants and that
    the concentration of omethoate is about 10 percent of the total two
    days after spraying, rising to 35-50 percent seventeen days after
    spraying.

    Oilseed Crops

    Cotton Seed

         De Pietri-Tonelli and Barontini (1961) carried out radiometric
    determinations of the chloroform-soluble extractives (i.e. dimethoate
    and omethoate) in the seeds of potted cotton plants raised in the
    glasshouse. The plants were sprayed with [32p]-dimethoate (0.2 g/l)
    when the bolls were nearly ripe. The analytical data (de 
    Pietri-Tonelli et al., 1965) showed that systemically translocated

    Table 14.  Dimethoate residues in tomatoes following a 30 second 
               dip in dimethoate emulsion (3 g/l)

                                                                  

                               Dimethoate residues (mg/kg)

    Time after dipping         Dip Only       Dip and Rinse
                                                                  

    1 day                      1.35           0.71

    3 days                     1.05           0.61

    7 days                     0.69           0.49
                                                                  

    Omethoate was not detected (<0.01 mg/kg)



        Table 15.  Residues of dimethaote in tomatoes dipped in dimethoate (0.5 g/l) 
               for 3 minutes

                                                                                    

    Experiment     Average Size      Interval              Residues (mg/kg)
    No.            of tomato         after                                          
                   (cm)              dipping,       (1)       (2)         Average
                                     days
                                                                                    

    1                8 cm               0           0.54      0.57        0.56
    2                6 cm               0           0.51      0.79        0.65
    3                7 cm               0           0.59      0.50        0.55
                                        3           0.71      0.62        0.67
                                        7           0.26      0.25        0.26
                                                                                    

    Omethoate was not detected.
    
    Table 16.  Dimethoate and omethoate in asparagus foliage

                                                                       

    Days after                          Residues, mg/kg (fresh wt)
    spray                            Dimethoate    Omethoate    Total
                                                                       

    1st spray (July 24, 1982)
    2                                11.0          1.00         12.00
    10                                1.01         1.02          2.03
    17                                0.21         0.43          0.64
    31                               Trace*        0.06          0.06
    46                               Trace         Trace        Trace

    2nd spray (Sept. 8, 1982)**
    2                                 4.43         0.45          4.88
    12                                0.71         0.65          1.36
    21                                0.17         0.52          0.69
    26                                0.36         0.18          0.54
    33                                0.12         0.38          0.50

    1st spray (July 29, 1982)
    5                                 5.14         1.62          6.76
    12                                0.43         0.48          0.91
    20                                0.08         0.29          0.37
    26                                0.02         0.04          0.06
    39                                0.10         Trace*        0.10

    2nd spray (Sept. 17, 1982)
    2                                22.4          2.12         24.5
    9                                 0.98         0.75          1.73
                                                                       

    * Trace = <0.01 mg/kg.
    ** Rained on Sept. 9, 1982, i.e., one day after the spray.


        Table 16a.  Residues of dimethoate and omethoate on and in wheat plants following application of dimethoate at 
                420 g ai/ha

                                                                                                                       

                 Days                             Residues, mg/kg at seeding dates
    Sampling     after             May 1                       May 15                     June 1
    Date         spray     Dimethoate   Omethoate     Dimethoate    Omethoate    Dimethoate    Omethoate
                                                                                                                       

    June 28        0        17.36       ND*            41.50        ND             63.18       ND
    29             1         7.08       T**            14.07        T              13.79       0.19
    30             2         5.19       0.45            9.96        0.96           10.39       1.32

    July 1         3         4.72       0.63            5.40        0.71            8.54       1.22
    2              4         4.25       0.62            4.86        0.74            5.46       0.90
    4              6         4.03       0.60            3.65        0.56            4.89       0.76
    5              7         3.99       0.58            2.70        0.49            2.97       0.55
    7              9         2.13       0.44            1.95        0.36            1.22       0.25
    11            13         0.64       0.25            0.55        0.19            0.12       0.06
    15            17         0.62       0.24            0.36        0.14            0.02       0.03
                                                                                                                       

    * ND = not detectable (less than 0.005 mg/kg.
    ** T = trace amounts (between 0.005 and 0.009 mg/kg)
    
    dimethoate and omethoate occurred inside the bolls both in the
    delinted seeds and in the lint. The residue was below 1 mg/kg 1 day
    after application and diminished in the following days but changed
    little between days 12 and 26, possibly owing to the competitive
    effects of degradation and systemic translocation.

         Llistro et al (1982) report that no residues were found in
    cotton seed 10 to 30 days after the last of 10 sprays, each at
    0.5-0.9 kg/ha.

    Mustard

         Verma (1980) in evaluating insecticides against pests of the
    mustard crop reported that dimethoate persisted to a level of
    0.08 mg/kg 6-29 days after spraying.

    Peanuts

         Studies carries out in India (Anon, 1977) indicated that
    following 2 sprays with dimethoate (0.3 g/l) the residue in peanut
    kernels was 0.48-0.55 mg/kg.

    Soybeans

         Beck et al. (1966) applied diluted dimethoate emulsion at the
    rate of 125, 250 and 500 g/ha and found that residues had decreased to
    0.1 mg/kg by the seventh day after treatment.

    FATE OF RESIDUES

         The fate of dimethoate residues was reviewed in the 1967
    evaluation and in the 1971 evaluation of omethoate. These include
    references and diagrams of the metabolic pathways in plants and
    animals. Additional material is reviewed below.

    In Animals

         Kaplanis et al. (1959) studied the metabolism of
    [32P]-dimethoate in cattle following oral and intra-muscular (i.m.)
    administration of 10 mg/kg. About 90 percent of the oral dose was
    eliminated in the urine after 24 hours. The same percentage of the
    i.m. dose was excreted after 9 hours. Only 3.7 to 5 percent of the
    oral dose and about 1 percent of the i.m. dose was eliminated in the
    faeces. The major metabolic products were dimethylphosphate,
    dimethylphosphorothioate, and several unknowns. Analysis of tissues
    from an orally treated calf showed only very low levels (0.02 mg/kg)
    of organo-extractable radioactive compounds present in brain, liver,
    testes, and lungs.

         After oral treatment with 10 mg/kg body weight, Plapp et al.
    (1960) reported residues in the fat of cattle obtained by biopsy as
    3 mg/kg after 3 hours and 0.1 mg/kg after 8 hours; 14 days after oral
    intake the values in all tissues had dropped to less than 0.1 mg/kg.

    Shortly after treatment with [32P]-dimethoate high concentrations were
    observed in the blood of cattle and these reached their maximum after
    1 hour for i.m. treatment and after 3 to 6 hours for oral treatment.

         The absorption, distribution, metabolism and excretion of
    [32P]-labelled dimethoate was studied in rats and 3 species of insects
    by Brady and Arthur (1963). Phosphorothioate oxidation occurred in
    rats, but degradation, rather than activation was predominant. Of the
    many compounds excreted by rats, dimethoate accounted for much less
    than 1 percent and omethoate for less than 5 percent. Amidase activity
    was more pronounced in rats than in insects immediately following
    treatment with dimethoate; this major metabolic difference may partly
    explain selectivity. Phosphatase activity was also more evident in
    rats than in insects.

         Morikawa and Saito (1966) studied the metabolism of dimethoate in
    insects, plants and mammals, in vivo and in vitro. The optimum
    pH for the degradation of dimethoate was approximately 8 for rat liver
    homogenate and 7 to 7.4 for insect homogenate. The hydrolysis of the
    S-C bond of dimethoate was specific to the rat liver homogenate.

         By means of TLC and colorimetric analysis, Mitsui et al.
    (1966) showed that when dimethoate was given to rats, the content in
    each organ was highest 2 hours after treatment. About 95 percent of
    the administered dose was hydrolysed in 7 days.

         Beck et al. (1968) studied the effect of feeding 
    dimethoate-treated silage, dimethoate and omethoate to cattle. The
    work is reviewed in the 1970 evaluation.

         Bazzi (1968) prepared a review of the metabolism of dimethoate in
    animals and plants and on the analytical methods for the assay of the
    insecticide and of its active and inactive metabolites, together with
    data on their acute toxicities.

         Menzer and Dauterman (1970) in a review of the metabolism of
    some organophosphorus insecticides pointed out that dimethoate is
    hydrolysed in liver by microsomal amidase and that this enzyme occurs
    at high concentrations in sheep liver. Studies have shown that the
    carboxyesterase responsible for the hydrolysis of malathion has no
    effect on dimethoate.

         Menzie (1974) reviewed the metabolism of a number of pesticides
    including dimethoate.

    In Plants

         Santi (1961) showed that dimethoate penetrates from the skin of
    peaches into the pulp, but more slowly than was observed in cherries.
    5 of 8 metabolites were identified.

         De Pietri-Tonelli and Barontini (1960g) showed that there is
    little movement of dimethoate deposits from fruit to other parts of
    the plant, but translocation from leaf to leaf may occur mainly upward
    through the xylem to young leaves, and to a limited extent downward.
    Treating sections of lemons with labelled dimethoate revealed little,
    if any, movement of the insecticide from the treated area, laterally
    or inwardly. This suggests that citrus peel from treated citrus crops
    used for cattle feed might contribute significant residues to animal
    fodder. Gunther et al. (1965) showed, however, that residues were
    lost during processing (see "Fate in processing and cooking").

         The penetration of dimethoate into plants was studied by de
    Pietri-Tonelli and Barontini (1960b, 1961) by applying aqueous
    solutions of labelled dimethoate to lemons, peaches and olives.
    Autoradiography of sections of the lemons showed that penetration of
    the phosphorus-containing metabolites was restricted to the peel; in
    peaches they penetrated through the pulp to the stone, and in olives
    the penetration included the stones if the olives were sprayed when
    unripe, but not if the olives were sprayed after the stones had
    hardened.

         In a series of tests with labelled dimethoate applied to the
    trunks of lemon trees, Santi (1962) found it was translocated mostly
    upward and deposited in varying amounts, large in leaves, medium in
    twigs and small in the skins of the fruit. Small quantities of
    unidentified [32P]-substances were found in the roots.

         Santi et al. (1962) found that the metabolism of dimethoate
    in leaves of sugar beets followed two courses: oxidative, with the
    formation of omethoate, and hydrolytic with the formation of 3
    phosphoric acids and a phosphorothioate. Four other [32P]-substances
    were recorded but not identified.

         Bull et al. (1963) treated cotton seedlings with labelled
    dimethoate. After 5 days, 60 percent of the absorbed insecticide had
    been degraded to 11 metabolites, all but 4 of which were identified.

         Kubel et al. (1966) studied the impurities in technical
    dimethoate and prepared experimental formulations of the technical
    active ingredient and the pure compound which they applied to
    greenhouse cucumbers. The resulting residues differed little in
    composition or residual life. Dimethoate and omethoate were the only
    residual compounds identified, omethoate appearing only in very small
    quantities.

         Mitsui et al. (1966) used thin-layer chromatography and
    spectrophotometry to study the fate of dimethoate applied to plants
    cultured in various concentrations of dimethoate emulsion for 20 hours
    and in plants treated with a granulated formulation. Following
    systemic uptake, the maximum concentration in plant tissues was
    6.59 mg/kg and this dropped below 0.1 mg/kg in less than 10 days after

    the removal of the insecticide source. When the dimethoate was applied
    to the plant leaf the uptake reached a maximum in approximately 10
    days and persisted for less than 25 days.

         Lucier and Menzer (1968) and Lucier (1967) investigated the
    metabolism of dimethoate in bean plants. Results are summarized in the
    1967 evaluation.

         Bazzi (1968) reviewed the metabolism of dimethoate in animals and
    plants and the analytical methods for the assay of the insecticide and
    its active and inactive metabolites, together with data on their acute
    toxicities (64 references).

         Lucier and Menzer (1970) showed that dimethoate undergoes
    oxidative N-demethylation with the formation of a hydroxymethyl
    intermediate leading to the production of an un-substituted amide
    metabolite. In this case, demethylation takes place with both
    dimethoate and omethoate. These authors reported that in bean plants
    the half-life of dimethoate was 1.7 days and that at harvest omethoate
    was the major organo-extractable metabolite, reaching a level of 7.3
    percent of the total residue after 3 days.

         Ishiguro and Saito (1971) applied 32P-labelled dimethoate to the
    water and soil in which rice plants were growing. They found that
    under conditions where the water was saturated with insecticide,
    radioactive metabolites of dimethoate moved to the aerial parts of the
    plants very rapidly, and accumulated in the leaf sheath and leaf blade
    in large amounts. From these results, it seems probable that
    dimethoate is not only absorbed through roots but also penetrates
    through the leaf sheath and is translocated in the plant tissues.
    Dimethoate was decomposed in the plant tissue. Metabolism was most
    active at the junction of aerial and root parts of the plants, and
    metabolites accumulated.

         Sauer (1972) showed that formothion, the N-formyl-N-methyl
    analogue of dimethoate, was metabolized to dimethoate in bean plants,
    but further oxidative demethylation did not occur.

         Steller and Brand (1974) analysed field-treated grape samples
    harvested 28 days after the last application of dimethoate and found
    less than 0.05 mg/kg each of what appeared to be des-N-methyl
    dimethoate, N-hydroxymethyl dimethoate, des-N-methyl omethoate and
    N-hydroxymethyl omethoate.

         Garrett (1980) studied the metabolism of N-hydroxymethyl
    dimethoate and N-demethyl dimethoate in bean plants but the paper, a
    111-page thesis, was not available for review.

         Wagner et al examined the metabolism of omethoate in sugar
    beets in greenhouse studies. A summary appears in the evaluation of
    omethoate.

    In soil

         Getzin and Rosefield (1968) measured dimethoate residues by
    gas-liquid chromatography 2 weeks after application to clay loam.
    Dimethoate was degraded to about the same extent in heat-sterilized
    and gamma-irradiated soil, 18 and 20 percent respectively. About
    7 percent of the dimethoate had been degraded after 2 weeks in 
    non-sterile soil.

         Graham-Bryce (1969) studied the diffusion characteristics of
    dimethoate in silty loam soil. Diffusion rates changed very little as
    the dimethoate concentration was increased, but increased rapidly as
    the soil moisture increased. There was little movement of dimethoate
    in soil, except under moist conditions.

         Harris and Hitchon (1970), in laboratory tests on the biological
    activity of several pesticides in soil, reported dimethoate to be
    moderately persistent, its biological activity disappearing after
    36 weeks. In dry sandy loam, 50 mg/kg was the lowest concentration at
    which dimethoate showed biological activity when applied as a soil
    treatment; in moist sandy loam the level was 10 mg/kg, and in high
    organic soil 100 mg/kg. The reported increase in cholinesterase
    inhibition shown by dimethoate in moist soil, as compared to dry, is
    probably due to the greater production of omethoate. Dimethoate and
    its metabolites rapidly disappeared from wet organic (muck) soil.

         Ishiguro and Saito (1971) showed that dimethoate yielded more
    chloroform- and water-extractable radioactivity than vamidothion,
    disulfoton, thiometon and mecarbam 6 days after application to soil.
    There was significantly less radioactive material adsorbed. The
    dimethoate-treated soil produced the highest level of biological
    activity against the small brown plant hopper fed on rice plants
    growing in the treated soil. Larger amounts of chloroform-partitioned
    metabolites of dimethoate were detected in the aerial and root parts
    of rice plants as compared with other test compounds.

         Kawamori et al. (1971a) studied the retention of dimethoate
    in 3 soils: a loamy sand, clay loam and a silty clay loam. In each
    soil, much less dimethoate was retained than disulfoton. Larger
    amounts were retained in the soils having higher organic matter
    content and cation exchange capacity. The amount of retained
    insecticide was related to the content of organic matter rather than
    clay in the soils.

         Kawamori et al. (1971a) studied the changes in the retention
    and metabolism of dimethoate in soils and showed that the amount of
    dimethoate retained initially was very small but increased rapidly
    during the first 2 days. Initially the insecticide was retained
    without degradation but was decomposed gradually during the succeeding
    period.

         Duff and Menzer (1973) studied the persistence and degradation of
    dimethoate in silty loam, loamy sand and clay loam. No major
    difference in total radioactivity recovered was noted between the 3
    soil types in two experiments. Moisture promoted more rapid
    disappearance of the dimethoate radioactivity. Downward movement of
    dimethoate was slightly more extensive in loamy sand than silty loam
    or clay loam and was increased by moisture in all three soils.

         In moist soils the conversion of dimethoate to omethoate was
    faster, and the level of omethoate was generally greater. The only
    hydrolytic metabolite identified was dimethoate carboxylic acid. Less
    than 1 percent of the applied radioactivity was recovered from the
    2.5-5 cm layer after 5 weeks under relatively dry conditions; however,
    residues were found as far down as 10 cm after 3 weeks under wetter
    conditions. Less than 0.5 percent of the applied dose was recovered
    from corn and bean plants grown in the soil.

         El Beit et al. (1977a) found that for a given application of
    dimethoate, the loss by leaching increased with soil type in the order
    clay < clay loam < sandy clay loam < sand. In general, the loss
    through leaching for a single soil type increased with the amount of
    dimethoate applied. Retention was greatest in the loam and least in
    the sand and was thought to be affected by physical forces and
    hydrogen bonding. The loss of the pesticide through evaporation,
    degradation and irreversible adsorption increased with the dosage
    applied. It was in the descending order clay > clay loam > sand
    >sandy clay loam > loam. However, the loss due to evaporation alone
    was in the order sand > sandy clay loam > clay loam > loam.
    Biological degradation of dimethoate was of little importance and
    depended on the type of soil as well as the type and number of 
    micro-organisms originally present in the soil.

         The same authors (El Beit et al. 1977b) reported that the
    residual accumulation of dimethoate increased with frequency of
    application, even under leaching conditions. Increasing the initial
    soil moisture content resulted in increased loss by leaching and a
    consequent reduction in the proportion of pesticide retained in the
    soil. Removal of soil organic matter reduced biodegradation of the
    pesticide but accelerated the loss by leaching, evaporation or
    co-distillation, so that the retention was reduced. Moist soil would
    help to make the pesticide available in solution for the control of
    soil pests and absorption by root crops.

         El Beit et al. (1978) found that pH, temperature and the type
    of medium are important factors affecting the stability of dimethoate
    in soils and solutions. Within the pH range 7-11, dimethoate
    degradation depends on the alkalinity of the medium rather than the
    time of storage. At pH 4.2 degradation is largely dependant on the
    length of time the dimethoate solution has been stored. Acid or salt
    concentration has little effect on the degree of degradation when the
    pH is maintained constant. Liming the soil results in a decrease in
    leachability and in retention of the pesticide by the soil.

         Alexander and Rosenberg (1979) were able to isolate bacteria from
    soil and sewage capable of utilizing dimethoate as the sole source of
    phosphorus. Extracts of 2 bacteria derived from organophosphate-grown
    cultures catalysed the disappearance of 5 organophosphorus compounds
    but not dimethoate.

         El Beit et al. (1981) made an extensive review of the factors
    affecting soil residues of dimethoate and 4 other widely used
    pesticides. They drew upon most of the above-mentioned papers together
    with the findings of some other workers.

    In Water

         Eichelberger and Lichtenberg (1971) studied the persistence of
    28 common pesticides in raw river water over an 8-week period. They
    found that dimethoate was much more stable in river water than other
    organophosphorus compounds such as parathion, malathion,
    carbophenothion and fenthion but about as persistent as ethion and
    just slightly less so than monocrotophos. It was significantly more
    persistent than any of the carbamate compounds tested though less
    stable than most of the organochlorine compounds. Following the
    addition of 10 ug/l, 50 percent of the dimethoate was recoverable at
    the end of 8 weeks. By comparison, only 50 percent of parathion and 25
    percent of malathion was recoverable from the same initial
    concentration at the end of the first week. No reasons were advanced
    for the stability of dimethoate, the molecule of which is
    unsymmetrical. The symmetry of the ethion molecule was advanced as an
    explanation of the stability of that compound.

         Kadoum and Mock (1978) analysed water and pit bottom soil in
    tailwater pits from irrigated corn and sorghum fields in Kansas, USA,
    for a wide variety of herbicide and insecticide residues. Dimethoate
    was one of the pesticides most likely to enter tailwater pits as a
    result of aerial application to the crops. However, no trace of
    dimethoate was found in 129 samples of pit bottom soil but it was
    detected in 10 of the 129 samples of tailwater at levels ranging up to
    0.0043 mg/l with a mean of 0.0019 mg/l. The analytical methods used
    had a limit of determination for dimethoate of 0.0001 mg/l. Residues
    of other pesticides occurred much more frequently and at levels up to
    50 times that reported for dimethoate.

         Noble (1984) studied the effect of pH and temperature on
    postharvest dip solutions of dimethoate (500 mg/l) by measuring the
    half-lives at pH4, 6, 8, 10 and 11.5 and at 25°C and 52°C. The 
    half-lives ranged from 206 days to 39 minutes at 25°C and 5.6 days to
    205 seconds at 52°C. A formula was developed which gives the half-life
    of the dimethoate as a function of pH and temperature.

    In Processing and Cooking

    Fruit

    Apples

         An abstract of a report by Antonovich and Vekshtein (1975)
    reports that washing in cold running water removes 64 percent of the
    dimethoate residue from apples whilst heating to 100°C for 15 or 30
    minutes reduces the residue by more than 85 percent. Processing into
    juices, jams or purees removes all trace of dimethoate residue from
    peeled fruit and reduces the content of unpeeled fruit by almost 100
    percent. The apples on which the studies were conducted contained
    0.06 mg/kg dimethoate. The original Russian reference was not
    available and the interpretation given in the abstract is questioned.

    Citrus

         Gunther et al. (1965) showed that no measurable amount of
    dimethoate could be removed by hand washing of Valencia oranges with
    dilute detergent. They also reported that most of the dimethoate
    residue in citrus peel was lost during processing into citrus pulp
    cattle feed (see Table 17).

         Albach and Lime (1976) studied the effect of preparing whole
    orange puree on the level of dimethoate in unwashed and washed Marrs
    oranges. The puree incorporates from 85 to 90 percent of the entire
    fruit into the final product. In the process, whole fruit are 
    water-blanched at 100°C for 10 minutes before grinding. This would be
    expected to eliminate a considerable portion of any residue that might
    be present in the fruit as picked. No residues of dimethoate were
    found in the unwashed, washed or pureed fruit. In the light of
    findings of other workers the validity of these results is questioned.

    Grapes

         Steller and Pasarella (1972) studied the level of residues in
    grapes, grape pomace, wine and raisins. The results are reported in
    Table 18.

         Kawar et al. (1979) report a study in which dimethoate was
    added to grape concentrate at the rate of 1 and 25 mg/kg prior to
    fermentation with yeast. The finished wine, 56 days later, contained
    0.98 and 21 mg/kg respectively of the dimethoate added to the grape
    must. Residues in wine stored at 24°C were hydrolysed with a half-life
    of 30 days. Residues were unchanged in wine in frozen storage for
    1 year.

    TABLE 17. Residues of Dimethoate Found in the Processing of Laboratory
              Valencia Pulp Cattle Feed

                                                                          

           Sample A                                     Sample B
                                                                       
    Moisture                                      Moisture
    %           mg/kg 1                           %             mg/kg
                                                                       

                         FRESH GROUND PEEL

    77.5        2.5                               80            2.6
    77.5        2.6                               80            3.2
    77.5        2.2                               80            2.0
    77.5        3.1                               80            2.3

                         DRIED CATTLE FEED

    14          2.2                               1             nil
    14          3.5                               1             nil
    14          2.7                               1             nil
    14          2.8                               1             nil
    14          2.2                               1             nil
    14          2.2                               1             nil
                                                                          

    1  All values were corrected for background and recovery of dimethoate
       added at the time of equilibration. Recovery from four samples of 
       fortified ground peel (2.0 to 4.0 mg/kg) was 76 +/- 4% and from four
       samples of final fortified cattle feed (4.0 to 8.0 mg/kg) was 
       81 +/- 10%.

    nil = less than 0.3 mg/kg.

    TABLE 18.  Residues of Dimethoate and Omethoate in Grapes, Grape 
               Pomace, Wine and Raisins

                                                                      

    Sample            Treatment 1            Residue, mg/kg
                                                                      
                                        Dimethoate         Omethoate
                                                                      

    Grapes               A              0.23               0.16
    Grapes               B              0.35               0.18

    Grape pomace         A              0.22               0.16
    Grape pomace         B              0.37               0.22

    Wine                 A              0.15               0.12
                         B              0.23               0.13

    Raisins              A              0.15               0.05
                         B              0.2                0.05
                                                                      

    1  Treatment: A-3 applications at 2.5 kg/ha.
                  B-2 applications at 2.5 kg/ha and finally at 5 kg/ha
                  at intervals of 28 days and 13 days, the last 28 days
                  before harvest.

    Miscellaneous Crops

    Olives

         Ramos and Costa (1960) studied residues of dimethoate in olive
    oil originating from olive plantations treated with dimethoate. The
    residues ranged from 0.3 mg/kg to 1 mg/kg. Analysis of preserved
    olives showed residues of dimethoate between 0.07 and 0.14 mg/kg. No
    reference was made in this work to the number of treatments nor to the
    interval between treatments and the collection of the samples. In
    another study (Ramos and Costa, 1962) olive oil made from olives
    containing 0.5 mg dimethoate/kg was found to contain a maximum of
    0.4 mg/kg.

         Santi and Giacomelli (1962) found that the concentration of
    dimethoate in olive oil represented about 1/3 to 1/4 of the
    concentration in the olive. Their results, quoted in detail by de
    Pietri-Tonelli et al. (1965) showed that dimethoate, omethoate and
    other products of hydrolysis were largely removed during the
    processing of the oil, while treatment of eating olives with NaOH as
    in the normal industry process extracted 80-90 percent of the
    dimethoate and metabolites present in the olives at the time of
    dipping. A further soaking of the olives in water for 5 days reduced
    the total radioactivity to 1-2 percent of that present in the olives
    at harvest time, and the chloroform-soluble residue effectively to
    zero.

         Many analyses of oil samples from numerous olive-growing areas
    have consistently shown the practical absence of dimethoate and
    omethoate. Alessandrini (1962), in an extensive review of insecticide
    residues in olive oil and table olives, reported that a large number
    of samples of olive oil analysed by the Italian Ministry of
    Agriculture contained no measurable dimethoate or omethoate. This was
    not unexpected because the coefficient of distribution of omethoate
    between water and oil is such that even when large quantities of the
    metabolite are deliberately added to the oil and the latter is simply
    washed with water the omethoate passes entirely into solution in the
    water.

         Albi and Rejano (1982) reported studies carried out in Spain
    showing that residues of dimethoate in olives ranging from 0.93 to
    0.95 mg/kg were completely eliminated after the initial treatment with
    2.36 percent NaOH solution during pickling.

    Bajra Grains (Pennisetum typhoides)

         Santharam et al. (1976) found that dimethoate, applied at the
    rate of 30 g/ha produced a residue at harvest of 0.65 mg/kg in the raw
    grain. Cooking reduced the residue level to 0.05 mg/kg as determined
    by the TLC method of Steller and Curry (1964).

    Silage

         Beck et al. reported a series of studies involving the
    application of dimethoate sprays to corn plants destined for silage
    for feeding to cattle. In one of these experiments dimethoate emulsion
    was sprayed on corn plants at the rate of 1 and 2 kg/ha. Samples were
    taken immediately the spray had dried and on the following day when
    the corn was cut and placed in silage pits. The silage was sampled
    8 times over the period when it had been in storage for 80 to 122
    days. The samples were analysed by a method based on the determination
    of total sulphur. It is believed that this method would not recover
    residues of omethoate. The results (Beck et al., 1968) showed that
    losses of residue that could be associated with 1 day of weathering in
    the field and harvesting amounted to 70-90 percent of the dose
    applied. Of that amount about 50 percent of the dimethoate residue
    ensiled was present after 80 days. However, the levels may have been
    influenced by downward translocation of residues in the silos and
    subsequent losses caused by the relatively small amount of seepage:
    e.g. 1 day after ensiling, dimethoate residues in seepage from the
    silos containing corn treated with 1 and 2 kg/ha were 4.9 and
    26.6 mg/kg respectively. In subsequent studies (same reference) corn
    treated at the rate of 500 g/ha and 2 kg/ha was fermented at 30°C for
    30 days before being analysed (by GLC) for dimethoate and omethoate.
    Silage from corn harvested 1 day after treatment with 500 g/ha had an
    average residue of 1.27 mg/kg dimethoate (0.6-2.1) and less than
    0.1 mg/kg of omethoate. Samples from the 2 kg/ha treatment at 1 day
    contained an average of 7 mg/kg (3.7-10.8 mg/kg) dimethoate and about
    0.2 mg/kg of omethoate. Samples of silage made 7 days after treatment
    at the high rate contained an average of 0.53 mg/kg dimethoate
    (0.350.74) and no omethoate (less than 0.01 mg/kg).

    Tea

         Manchanda and Dougan (1975) studied the level and fate of
    radiolabelled dimethoate applied to tea plants. The experimental
    formulation was applied to 2 leaves and a leaf bud. After 2 weeks the
    leaves to which the pesticide had been applied were plucked and
    processed to simulate the conditions used in commercial tea
    manufacture. The tea from each sample was treated with boiling water
    (20 ml/g of tea) and, after standing for 10 minutes with occasional
    agitation, was filtered. The residue was washed with several
    quantities of boiling water and the filtrates combined. The aqueous
    infusion contained 52 percent of the activity present in the processed
    leaves. About 15 percent of the radioactivity was due to the presence
    of dimethoate and about 25 percent to omethoate. N-demethyl dimethoate
    and the acids of dimethoate and omethoate which have both been
    reported as metabolites in plants were also confirmed to be present by
    GCMS.

    Vegetables

    Beans

         An abstract of a study by Bognar (1977) in the Federal Republic
    of Germany into the fate of pesticide residues in vegetables following
    preparation and cooking indicates that more than 82 percent of the
    dimethoate present in fresh beans is removed by washing and cooking.
    Agnihothrudu and Mithyantha (1978) report extensive studies carried
    out in India (Anon, 1977) in which 14 separate samples of French beans
    containing known amounts of dimethoate residues were cooked in the
    normal manner, resulting in a loss of 87 percent (75-95.5 percent) of
    the residues.

    Cabbage

         Kaemmerer and Buntenkotter (1973) recorded that Askew and
    Mitchell (1968) found a 44-52 percent loss of dimethoate from cabbage
    cooked for 30 minutes.

         Krishnaiah and Rattan Lal (1973) reported that washing cabbage
    heads reduced the level of dimethoate residues by an average of 40
    percent (21.151.8 percent).

    Cauliflower

         Krishnaiah and Rattan Lal (1973) showed that washing cauliflower
    curds reduced the dimethoate residue by an average of 32 percent
    (18.5-48.4 percent) and Bognar (1977) found that approximately 82
    percent of the dimethoate present in fresh cauliflowers was removed by
    washing and steaming.

    Chillies

         In studies carried out in India (Anon, 1977), 91 percent of the
    dimethoate residues present in green chillies were removed by washing.
    Details of the interval between application and harvest and the method
    of washing are not available.

    Chicory

         Ten Broeke and Dornseiffen (1973b) studied the effect of washing
    and boiling (as practised in the kitchen) on the level of dimethoate
    and omethoate in Witloof chicory. They showed that 32 percent of the
    dimethoate and 22 percent of the omethoate was removed by washing and
    63.4 percent of the dimethoate and 60 percent of the omethoate by
    washing and boiling. (Table 19.)

    TABLE 19.  Dimethoate and Omethoate Residues in Chicory Before and 
               After Washing and Cooking

                                                                         

                    Dimethoate                       Omethoate
                                                                          
    Sample   Before   After     After        Before    After     After
    No.      Washing  Washing   Cooking      Washing   Washing   Cooking
                                                                         

    1        0.11     0.07      0.04         0.11      0.09      0.04
    2        0.15     0.08      0.04         0.14      0.11      0.05
    3        0.12     0.08      0.04         0.11      0.09      0.05
    4        0.11     0.07      0.04         0.12      0.12      0.05
    5        0.13     0.11      0.07         0.13      0.14      0.09

    6        0.14     0.11      0.06         0.18      0.16      0.08
    7        0.13     0.09      0.05         0.14      0.11      0.06
    8        0.15     0.10      0.06         0.14      0.12      0.06
    9        0.14     0.09      0.05         0.19      0.13      0.07
    10       0.18     0.10      0.05         0.18      0.09      0.03

    11       0.17     0.11      0.05         0.15      0.09      0.04
    12       0.14     0.10      0.05         0.14      0.08      0.04
    13       0.12     0.10      0.05         0.17      0.14      0.11
    14       0.10     0.08      0.04         0.12      0.14      0.06
    15       0.11     0.08      0.04         0.16      0.09      0.05

    Average  0.14     0.09      0.05         0.15      0.12      0.06
                                                                         

    Egg plant

         Khaire et al (1983) reported that following treatment in the
    field with dimethoate at the rate of 0.3-0.6 g/l the residues in egg
    plant (brinjal) fruit were reduced by 23.3-96.1 percent by washing and
    by 52.3-95.7 percent by washing and cooking.

    Potatoes

         Kaemmerer and Butenkotter (1973) quoted Askew and Mitchell (1968)
    as reporting that 30 minutes cooking of potatoes reduced the
    dimethoate content by 22 to 39 percent.

         Misra et al,(1981) reported that washing and peeling reduced
    residues to about 20 percent of the concentration in the unwashed and
    unpeeled potatoes. Boiling the washed, peeled potatoes apparently
    destroyed all the remaining residue as none was detected in potatoes
    or water in which the washed potatoes were boiled. The limit of
    determination was not mentioned (Table 20).

    Tomatoes

         Agnihothrudu and Mithyantha (1978) reported official trials in
    India (Anon, 1977) in which washing tomato fruit reduced the
    dimethoate residue by 72 percent (1.8 reduced to 0.48 mg/kg).

    METHODS OF RESIDUE ANALYSIS

         Early methods were reviewed by de Pietri-Tonelli et al.
    (1965) and/or in the 1976 evaluation.

         The ad hoc Working Group on methods of analysis of the Codex
    Committee on Pesticide Residues at its meeting in 1983 issued
    recommendations for methods of residue analysis, which included
    dimethoate and omethoate, in foods. In the references given below,
    those methods which cover omethoate as well as dimethoate are marked
    with an asterisk. The primary recommendations were for methods which
    had been collaboratively tested. These included:

         Pesticides Analytical Manual, 1979*; Manual on Analytical
         Methods, 1973/1984; Anon, 1982*; Abbott et al., 1970*; Ambrus
         et al., 1981; Panel, 1977*; Panel, 1980.

         The Working Group also recognised that a number of other methods
    which had not been collaboratively tested were probably suitable for
    regulatory purposes and merited consideration. These include:

         Anon., 1982*; Carson, 1981; Eichner, 1978*; Krause and Kirchoff,
         1970; Mestres et al., 1977a, 1979; Specht and Tillkes, 1980*;
         Steller and Pasarella 1972*; Wagner and Frehse, 1976*.


        TABLE 20.  Dimethoate Residues in Potatoes

                                                                                                   

                                      Average residues (mg/kg dimethoate) 2
                                                                                                   
    Sampling       Unwashed and        Washed and          Washed, boiled      Water in which
    (days) 1       unpeeled potatoes   peeled potatoes     and peeled          washed potatoes
                                                           potatoes            were boiled
                   A         B         A         B         A         B         A         B
                                                                                                   

    Autumn Crop, 1976-77

    10             20.3      2.73      0.44      0.57      nd        nd        nd        nd
    15             1.27      1.53      0.28      0.32      nd        nd        nd        nd
    20             0.69      0.87      0.08      0.08      nd        nd        nd        nd
    25             0.43      0.51      0.02      0.03      nd        nd        nd        nd
    30 3           0.08      0.14      nd        nd        nd        nd        nd        nd

    Spring Crop, 1977

    10             1.87      2.11      0.27      0.33      nd        nd        nd        nd
    15             0.98      1.07      0.21      0.23      nd        nd        nd        nd
    20             0.61      0.67      0.95      0.06      nd        nd        nd        nd
    25             0.21      0.33      nd        0.02      nd        nd        nd        nd
    30 3           0.06      0.09      nd        nd        nd        nd        nd        nd
                                                                                                   

    1  After last spraying.
    2  Average of three replications.
    3  At harvest.
    nd  = Residues not detected.
    A  =  300 g dimethoate a.i. per ha per spray treatment.
    B  =  500 g dimethoate a.i. per ha per spray treatment.
    

         The Working Group also recommended a number of methods which
    could be used for confirming the identity of residues determined by
    the above methods. These included:

         Pesticides Analytical Manual, 1979; Safe and Hutzinger, 1979*;
         Cabras et al., 1979; Greehalgh and Kovacicova, 1975; Mestres
         et al., 1977b*.

    Other publications include the following:

    TLC:      Mitsui et al, 1966; Joint Dimethoate Residues Panel,
              1968; Kosmatyi et al, 1969; Zadrozinska, 1973;
              Antonovich and Vekshtein, 1975; Chakrabarti et al.,
              1975; Curini et al., 1980; Segovia and Hernandez, 1981b.

    GLC:      Bazzi 1968; Joint Dimethoate Residues Panel, 1968; Baumler
              and Rippstein 1969; Steller and Brand, 1974; Laski, 1974;
              Woodham et al., 1974a,b; Manchanda and Dougan, 1975;
              Smart et al., 1978; Le Bel et al., 1979; Ripley et
              al., 1974; Ferriera and Fernandez, 1980; Iwata et al.,
              1981; Lee and Westcott, 1981; Segovia and Hernandez,
              1981a,b; Holland and McGhie, 1983; United Kingdom, 1984.

         Methods based on high performance liquid chromatography (HPLC)
    have been included in the Pesticides Analytical Manual (1979) and in
    the corresponding manual of the Federal Republic of Germany (Anon.,
    1982).

         Mass spectrometry, combined with gas chromatography, has been
    used by Manchanda and Dougan (1975), Lee and Westcott (1979) and
    Cairns et al. (1984), qualitatively and/or quantitatively.

         Chakrabarti et al (1982) published a method for the
    determination of dimethoate in formulations and its residues in foods
    by gel electrophoresis. The tissue extracts are first subjected to
    hydrolysis. It is possible that the results include both dimethoate
    and omethoate. The minimum detectable limit is 0.1 mg and the method
    is reported to be simple and quick.

         An isotope dilution method employing [32p]-dimethoate and a
    liquid scintillation counter was developed by Luther et al.
    (1974). The authors reported this to show a 99.5-100.1 percent
    recovery of dimethoate. Analyses performed by this method would not
    record the level of omethoate.

    RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION

         The Netherlands Government supplied comprehensive information
    from surveys conducted by the Food Inspection Service on Witloof
    chicory and other commodities produced in The Netherlands and
    imported. These results are presented in Table 21 (Netherlands
    1981a,b, 1984). It should be noted that the national MRLs were changed
    during the period for which the data apply.


        TABLE 21a.  Dimethoate & Omethoate Residues Found in Food Monitoring in The Netherlands

                                                                                                                                               

    Dimetholate (D)
    +
    Omethoate (O)

    Source
    Netherlands (N)               1973      1973      1974      1974      1978      1979      1980      1982      1982      1982      1982
    Imported (I)                  Witloof   Witloof   Witloof   Witloof   Witloof   Witloof   Witloof   Witloff   Apples    Apples    Cherries
                                  (N)       (N)       (N)       (N)       (N)       (N)       (N)       (N)       (N)       (I)       (I)
    Residue                       D         O         D         O         D+O       D+O       D+O       D+O       D+O       D+O       D+O
                                                                                                                                               

    mg/kg

    0.000                          -         -          -        -         33        32         8
    0.001-0.200                   38        51         23       31        148       192       101       60        2         8
    0.201-0.400                   21         6         15        1         39        47        38       17                            1
    0.401-0.600                                                            19        10        20        5

    0.601-0.800                                                             9         9         5        1
    0.801-1.000                    7                    5                   5        13         0
    1.001-1.500                                                             8         8         3        1
    1.501-2.000                    2                                                  3         1
    2.001-2.500                                                                       3                  1
    2.501-3.000                                                                       2
    > 3.000                                                                          4

    TOTAL                         68        57         53       32        262       323       176       85        2         8         1

    > National MRL                9         0          5        0         22        42         9        3
                                                                                                                                               

    TABLE 21b.

                                                                                                                                               

    Dimetholate (D)
    +
    Omethoate (O)

    Source
    Netherlands (N)     1982      1982      1982      1982      1982         1982        1982        1982        1982         1982
    Imported (I)        Currants  Orange    Plums     Plums     Raspberries  Endive      Lettuce     Mushrooms   Parsley      Turnips
                        (I)       (I)       (N)       (I)       (N)          (N)         (N)         (N)         (N)          (N)
    Residue             D+O       D+O       D+O       D+O       D+O          D+O         D+O         D+O         D+O          D+O
                                                                                                                                               

    mg/kg

    0.000                                                                                1
    0.001-0.200                   1                                                                  1           1
    0.201-0.400                             1                                                                                 1
    0.401-0.600         1                             1

    0.601-0.800
    0.801-1.000
    1.001-1.500                                                 1
    1.501-2.000                                                                          1
    2.001-2.500
    2.501-3.000                                                              1
    > 3.000                                                                             1
                                                                                         (7.9)

    TOTAL               1         1         1         1         1            1           3           1           1            1

    > National MRL
                                                                                                                                               
    
         The Swedish Government (Sweden, 1984) provided information from
    the monitoring of domestic and imported foods by the National Food
    Administration. Table 22, which summarizes this information, does not
    indicate the total number of samples in which dimethoate or omethoate
    residues were detected, but it clearly indicates that the number of
    samples with residues above 0.4 mg/kg was small. Over the 3 years from
    the beginning of January 1981 to the end of 1983 seven of 1017 samples
    of Swedish Commodities (0.69 percent) were found to contain dimethoate
    residues above 0.41 mg/kg and 19 of 2582 (0.74 percent) of imported
    commodities contained dimethoate above this level. None of these
    exceeded the Swedish MRL for fruit and vegetables of 2 mg/kg.

         The Government of the United Kingdom (United Kingdom, 1984)
    provided information about residues in lettuce gathered from food
    monitoring during 1981/82 as indicated in Table 23. A significant
    proportion of the samples (8.6 percent) were found to contain
    dimethoate/omethoate residues. However only 2 of the 302 samples
    contained combined residues exceeding the current recommended MRL of
    2 mg/kg.

         The levels of dimethoate and omethoate in the samples containing
    determinable residues are shown in Table 24.

         The samples were analysed by a multi-residue procedure.
    Recoveries from spiked lettuce were 80 percent and the limit of
    detection was 0.01 mg/kg. All residues reported were confirmed using
    two GLC columns of different polarities as well as by the relative
    responses of alkali-flame and flame photometric detectors.

         The UK Ministry of Agriculture, Fisheries and Food (United
    Kingdom, 1984) examined 24 samples of apples, pears and plums that had
    been treated with dimethoate 11 to 126 days before harvest. Only in
    one sample of pears did the combined residue exceed the limit of
    determination (0.01 mg/kg dimethoate and 0.02 mg/kg omethoate). This
    contained 0.13 mg/kg of omethoate. The pears in question had been
    treated only 11 days before harvest.

         The Government of Denmark (Denmark, 1984b) reported that in the
    monitoring of pesticide residues in fruit and vegetables they
    frequently find small residues of dimethoate or omethoate, mainly in
    imported fruit. Seldom are dimethoate and omethoate residues present
    in the same sample. Over the period 1976-1984 the only samples
    containing both dimethoate and omethoate were the 14 listed in Table
    25.


        TABLE 22.  Results of Residue Monitoring in Sweden, 1981-1984

    Pesticide: Dimethoate

                                                                                                                  

                                       Number of          Number of samples with residues          Highest
    Food                Origin         samples               within given ranges, mg/kg            residue
                                       analysed       n.d.-0.41      0.41-1.03      1.04-2.05      mg/kg
                                                                                                                  

    Apple               Sweden            385           379             6                          0.85
                        Import            915           914             1                          0.56

    Cabbage             Sweden            126           125             1                          0.60
    Chinese             Import            191           191

    Cherries            Sweden              9             9
                        Import             52            46             4              2           1.4

    Chicory             Import             26            19             5              2           1.4
     leaves

    Cucumber            Sweden            312           312
                        Import            416           414             2                          0.71

    Grapes              Import            452           451             1                          0.47

    Lettuce             Sweden            185           185
                        Import            179           178             1                          0.98

    Mandarin            Import            351           350             1                          0.57

    Total               Sweden           1017                           7
                        Import           2582                          15              4

    Grand Total                          3599                          22              4
                                                                                                                  

    Swedish MRL - Fruit and Vegetables:  2 mg/kg
    Potatoes:  0.2 mg/kg
    
    TABLE 23.  Dimethoate/omethoate Residues in Lettuce

                                                                        

                      Total number    Residue range    Number in range
                        analysed          mg/kg
                                                                        

    Dimethoate
    UK-produced            65          0.01-0.1               7
                                       0.11-0.5               4
                                       1.9                    1

    Imported               86          0.14, 1.48             2

    Omethoate
    UK-produced            65          0.01-0.1               7
                                       0.16, 0.27             2

    Imported               86          0.07, 0.74             2
                                                                        



    TABLE 24.  Dimethoate/omethoate Residues in Lettuce

                                                                     

    Samples        Dimethoate residue        Omethoate residue
    No.                  mg/kg                     mg/kg
                                                                     

    EL1                  0.15                      0.04
    EL2                  0.09                      0.04
    EL8                  0.50                      0.09
    EL9                  0.10                      0.04

    EL36                 1.90                      0.27
    EL37                 0.08                     <0.05
    EL43                 0.05                      0.06
    EL65                 0.12                      0.09
    EL69                 0.34                      0.16

    DL5                  1.48                      0.74
    FL41                <0.05                      0.20
    SL51                 0.14                      0.07
    SL60                 0.05                     <0.05
                                                                     

    TABLE 25.  Samples of Fruit and Vegetables Found to Contain both
               Dimethoate and Omethoate Residues (Denmark, 1976-1948)

                                                                        

    Commodity                Dimethoate (mg/kg)     Omethoate (mg/kg)
                                                                        

    Cherries (Italy)               0.02                  0.12
       "        "                  0.19                  0.22
       "        "                  0.07                  0.08
       "        "                  0.05                  0.14
       "        "                  0.51                  0.09

    Apples (France)                0.09                  0.05
       "        "                  0.10                  0.04
       "        "                  0.13                  0.02
       "   (Italy)                 0.06                  0.11
       "        "                  0.41                  0.15
       "   (Netherlands)           0.02                  0.21

    Grapes (Italy)                 0.08                  0.11

    Satsumas (Spain)               0.02                  0.07

    Lettuce (USA)                  0.04                  0.04
                                                                        


        NATIONAL MAXIMUM RESIDUE LIMITS REPORTED TO THE MEETING

    The meeting was informed that the following national MRLs had been established.

                                                                                                            

    Argentina            dimethoate                        apple, pear.                                  1
                                                           pea, broccoli, lettuce, pepper
                                                           cabbage, savoy cabbage,
                                                           cauliflower, ruff, spinach,
                                                           chick-pea, broad bean, tomato.                2

    Australia            dimethoate (including             tomatoes, peppers.                            1
                         its oxygen analogue)              fruits, vegetables (except
                                                           tomatoes, peppers).                           2
                                                           oilseeds.                                   0.1
                                                           peanuts, eggs, meat, raw
                                                           cereals.                                   0.05

    Austria              dimethoate ) total
                                      omethoate            vegetables, fruit.                          1.5
                         omethoate  ) not over
                                      0.4 ppm
                                    ) total
                                      omethoate            grains, sugarbeets.                         0.2
                                    ) not over
                                      0.05 ppm             other.                                      0.1

                         omethoate                         vegetables, fruit,
                                                           sugarbeets.                                 0.4
                                                           other.                                     0.05

    Belgium              dimethoate                        fruit, vegetables.                            1

                         omethoate                         fruit, vegetables.                          0.2
                                                           artichokes, cherries, witloof,
                                                           spinach.                                    0.4
                                                           berries, onions, leeks,
                                                           root vegetables.                            0.1
                                                           cereal grains.                             0.05

    Canada               dimethoate (Cygon,                apples, broccoli, beet greens,
                         Rogor)                            cabbages, cauliflower, kale,
                         O,O-dimethyl S-methyl-            lettuce pears, spinach, Swiss
                         carbamoyl methyl                  chard, turnip greens.                        2*
                         phosphorodithioate
                                                           citrus fruit.                              1.5*

                                                           beans, blueberries, celery,
                                                           cherries, strawberries.                    1.0*

                                                           peas, peppers, tomatoes.                   0.5*

    Czechoslovakia       dimethoate - as                   tomatoes, green peppers.                      1
                         dimethoate (including             vegetables, fruits, including
                         the oxygen derivative)            citrus fruit.                                 2

    Denmark              dimethoate - total of             berries and small fruits,
                         dimethoate & omethoate            pome and stone fruits,
                                                           vegetables.                                   2

                         omethoate                         berries and small fruits, pome
                                                           and stone fruits, vegetables.               0.5
                                                           potatoes.                                  0.05

    * including the metabolite omethoate.

    EEC                  dimethoate                        all products.                                 1

                         omethoate                         cherries, witloof chicory,
                                                           artichokes, spinach.                        0.4
                                                           berries, onions, leeks,
                                                           root vegetables.                            0.1
                                                           other products.                             0.2

    Finland              dimethoate and                                                                0.5
                         omethoate, total

    France               dimethoate                        all fruits & vegetables.                    1.5
                         omethoate                         all fruits & vegetables.                    0.4

    German               dimethoate - max 20%              cereals.                                   0.05
    Democratic           as oxy compound                   pome, stone & small fruits,
    Republic                                               strawberries, citrus, root
                                                           vegetables, leaf vegetables,
                                                           cole crops, pulses.                         0.5
                                                           vegetable fruit                             0.5
                                                           sprout vegetables.                          0.1
                                                           other foods.                                  0

    German               dimethoate                        vegetables, fruits.                           1
    Federal                                                cereals, sugarbeets.                        0.2
    Republic                                               other vegetable foodstuffs.                 0.1

                         omethoate                         artichokes, chicory, cherries,
                                                           spinach.                                    0.4
                                                           small fruits, leeks, onions,
                                                           root vegetables.                            0.1
                                                           other vegetables and fruits.                0.2
                                                           other vegetable foodstuffs.                0.05

    Hungary              dimethoate                        green pepper, tomato,
                                                           currant, strawberry.                          1
                                                           apple, Brussels sprouts, cherry,
                                                           potato (unpeeled), apricot,
                                                           cabbage, kohlrabi, cauliflower,
                                                           savoy, pear, peach, parsley,
                                                           lettuce, sorrel, spinach, plum,
                                                           celery leaf.                                  2

                         omethoate                         apple, cherry, apricot,
                                                           pear, peach, plum, grape.                    2*

    India                dimethoate                        fruit, vegetables.                            2
                         (residues to be determined
                         dimethoate and its oxygen
                         analogue and expressed as
                         dimethoate)

    Ireland              dimethoate                        all products.                                 1

    Israel               dimethoate                        tree fruits (including citrus
                                                           fruit), eggplant, cucurbits,
                                                           peas, beans, vegetables.                      2
                                                           tomatoes, peppers.                            1

                         omethoate                         citrus fruit.                               0.4

    Italy                dimethoate                        fruits, vegetables, sugarbeets.             1.5
                                                           cereals.                                    0.2

                         omethoate                         fruits, sugarbeets, vegetables.            0.4*
                                                           cereals.                                   0.05

    Japan                dimethoate                        persimmon, summer orange (pulp),
                                                           summer orange (peel), mandarin
                                                           orange, potato, tomato.                       1

    Kenya                dimethoate                        tree fruit (including citrus).                2
                                                           maize, millets, sorghum,
                                                           tomatoes, peppers.                            1
                                                           other vegetables.                             2

                         omethoate                         apples, beans, broccoli,
                                                           cabbage, cauliflower, collards,
                                                           endive (escarole), kale, lemons,
                                                           lettuce, oranges, pears, peas,
                                                           peppers, spinach, Swiss chard,
                                                           tomatoes, turnips.                            2
                                                           melons.                                       1
                                                           potatoes.                                   0.2
                                                           pecans.                                     0.1
                                                           wheat grain.                               0.04
                                                           meat, fat and meat by-products
                                                           of cattle, goats, hogs, horses
                                                           and sheep.                                 0.02

    Mexico               dimethoate                        alfalfa, celery, broccoli, peas,
                                                           chili peppers, cabbage, citrus
                                                           fruit, spinach, string beans,
                                                           lettuce, tomato, apples, pears,
                                                           soybeans (forage and hay), wheat
                                                           (forage and straw).                           2
                                                           corn (forage), melons, grapes.                1
                                                           corn (grain).                                1N
                                                           potatoes, sorghum (forage).                 0.2
                                                           safflower, sorghum (grain)
                                                           nuts, cottonseed.                           0.1
                                                           soybeans (grain).                          0.05
                                                           wheat (grain).                            0.04N

    Netherlands          dimethoate                        fruit, vegetables (not
                                                           potatoes), spices.                            1

                         omethoate                         fruit, vegetables (not
                                                           potatoes), spice.                           0.2
                                                           Belgian endive (chicory),
                                                           spinach, cherry, artichoke.                 0.4
                                                           strawberry, berry, leek,
                                                           onion, carrot greens.                       0.1

    New Zealand          dimethoate                        tomatoes.                                     1
                                                           other fruit and vegetables.                   2

    Singapore            dimethoate                        fruits.                                     0.5
                                                           olives.                                       1

    South Africa         dimethoate (sum of                apples, beans, citrus, cruici-
                         dimethoate and                    ferae, cucurbits, grapes, peaches,
                         omethoate)                        pears, plums, sorghum and wheat.              2
                                                           cottonseed and groundnuts.                  0.1
                                                           potatoes, strawberries and
                                                           pineapples.                                 0.5
                                                           apples, Grapes and pears.                   1.5
                                                           citrus and lucerne.                           2
                                                           peas.                                         1

    Spain                dimethoate                        fruit, vegetables.                       1.5(2)

                         omethoate                         fruit, vegetables.                          0.4

    Sweden               dimethoate including              fruit and vegetables,
                         oxygen analogue (of               except potatoes.                              2
                         omethoate)                        potatoes.                                   0.2

                         omethoate                         citrus fruit.                               0.5
                                                           fruit and vegetables,
                                                           except potatoes.                            0.2

    Switzerland          dimethoate                        fruit (except cherries).                    0.5
                                                           vegetables.                                 0.3
                                                           cherries.                                   0.8
                                                           beets.                                     0.05
                                                           milk.                                     0.005

    Taiwan               dimethoate                        citrus fruit.                                 2

    USA                  dimethoate (Cygon,                dried citrus pulp.                           5*
                         Rogor)                            alfalfa, apples, beans (dry,
                         O,O-dimethyl S-methyl-            lima, snap), broccoli, cabbage,
                         carbomoly methyl                  cauliflower, celery, collards,
                         phosphorodithioate                endive (escarole), grapefruit,
                                                           kale, lemons, lettuce, mustard
                                                           greens, oranges, pears, peas,
                                                           peppers, soybean forage and hay,
                                                           spinach, Swiss chard, tangerines,
                                                           tomatoes, turnips (roots and tops),
                                                           wheat (green fodder and straw).              2*

                                                           corn fodder and forage,
                                                           grapes, melons.                              1*

                                                           potatoes, sorghum forage.                  0.2*

                                                           cottonseed, pecans, safflower
                                                           seed, sorghum grain.                       0.1*

                                                           corn grain.                                 0.1
                                                           (negligible residues)

                                                           soybeans.                                 0.05*
                                                           (negligble residues)

                                                           wheat grain.                              0.04*
                                                           (negligible residues)

                                                           eggs, meat, fat, and meat
                                                           by-products of cattle,
                                                           goats, hogs, horses,
                                                           poultry and sheep.                        0.02*
                                                           (negligible residues)

                                                           milk.                                    0.002*
                                                           (negligible residues)

    * including its oxygen analog O,O-dimethyl S-(N-methylcarbamoylmethyl) phosphorothioate

    USSR                 phosphamide (Rogor,               fruits, citrus fruits.                      1.5
                         dimethoate)

    Yugoslavia           dimethoate                        edible olives, fruit, vegetables.             1
                                                           other food commodities.                     0.5

                         omethoate                         vegetables and fruit.                       0.5
                                                           sugarbeets and other food
                                                           commodities.                               0.05
                                                                                                            
    
    APPRAISAL

         Following requests made at the 1980, 1981 and 1983 meetings of
    CCPR that, if possible, separate MRLs should be proposed for
    dimethoate and omethoate when the latter is used directly as an
    insecticide as well as when it occurs as a metabolite of dimethoate
    and formothion, a review was made of the published scientific
    literature as well as limited unpublished information available to the
    meeting. This included all information published since 1960 that was
    accessible and which had not already been evaluated by JMPR.

         Information on current uses in 11 countries indicated
    considerable similarity in rates of application but important
    differences in preharvest intervals. There is considerable overlap in
    the use of dimethoate and omethoate when viewed world-wide though in
    individual countries the uses may not coincide closely.

         The convention which has been accepted from the early days of the
    development of dimethoate that the residue should be expressed as the
    sum of the parent and metabolite has meant that most of the residue
    data has not indicated the relative proportions of dimethoate and
    omethoate. Furthermore, many of the analytical methods that have been
    widely used measured total phosphorus by colorimetric procedures. This
    has no doubt caused authorities to wonder whether omethoate occurs as
    a relatively high proportion of the total residue.

         A concerted effort has therefore been made to locate and evaluate
    all available reports of studies in which the concentration of both
    dimethoate and omethoate have been reported. In all of these studies
    it is clear that omethoate is produced within one day of treating
    crops with dimethoate dusts, wettable powders, or emulsion sprays. The
    concentration of omethoate remains low and relatively constant for
    periods as long as 35 days. The concentration of dimethoate falls
    rapidly during the first 7 days and thereafter, at a steady rate until
    it eventually reaches a level comparable with the concentration of
    omethoate. Thereafter the concentration of dimethoate continues to
    decline whilst the omethoate remains relatively constant. Thus, the
    proportion of omethoate in the total residue ranges from 1-2 percent
    initially, 10-15 percent during most of the post-treatment period,
    rising to approximately 50 percent after 35 days when the total
    residue level is of the order of 0.1-0.2 mg/kg.

         When omethoate is applied directly to these or similar crops the
    initial deposit of approximately 20 mg/kg declines within a few days
    to about 5 mg/kg and to between 2 mg/kg and 1 mg/kg by the 14th day
    after treatment. This level is 10-50 times the level which occurs from
    the metabolism of dimethoate applied to the same crops.

         It is noteworthy that several investigators have failed to detect
    omethoate residues in some fruits and vegetables following the
    application of dimethoate. This was reported for strawberries, citrus
    (edible portion), Brussels sprouts from preharvest application, and
    tomatoes and bananas following postharvest treatment.

         The information from residue trials made available from this
    review was evaluated to determine residue levels which would be
    appropriate for use in the establishment of MRLs. Data from trials on
    apples, apricots, black currants, cherries, citrus, grapes, peaches,
    plums, strawberries, olives, beans, Brussels sprouts, cabbage,
    cauliflower, chicory, peanuts and soybeans were available. With the
    exception of information on olives, all other data strongly supported
    the existing recommendations for MRLs when considered in the light of
    the PHI's adopted in most countries for these crops. The data from
    trials on olives would suggest that the MRL could be reduced to
    0.5 mg/kg if the olives were not harvested until 30 days after the
    last spray.

         Considerable information on the metabolism of dimethoate in
    animals, plants and soil and on the fate of dimethoate in animals and
    soil was available to the meeting. There appears to be only a remote
    possibility of omethoate residues being excreted in milk following the
    feeding of dimethoate treated fodder, silage or agricultural wastes to
    dairy cows. The level in the milk is not likely to exceed 0.1 mg/kg.

         It is clear that residues of dimethoate are taken up by crop
    plants following the application of dimethoate to the soil but the
    levels appear to be well within the limits already recommended for
    dimethoate and omethoate residues in the corresponding commodities.

         There was a substantial amount of information available on the
    effect of processing and cooking on dimethoate residues in fruit,
    vegetables, olives and grapes. The preparation of citrus juice
    eliminates most, if not all, of the dimethoate from whole citrus. As
    far as could be determined from the several studies available, no
    omethoate is found in the juice of citrus. Dimethoate residues are
    eliminated when treated apples are processed into juice, jam or puree.
    Dimethoate residues on grapes find their way into grape juice and wine
    without change in composition or concentration but during storage of
    wine the residues completely degrade. There is a significant loss of
    the omethoate component during the processing of raisins but the
    dimethoate residue appears to remain at about the same concentration
    in the dried fruit as in the fresh fruit if no allowance is made for
    the water lost in the process.

         The processing of olives for the recovery and refining of olive
    oil eliminates virtually all traces of dimethoate and omethoate
    residues. The process of pickling olives for eating removes and
    destroys substantially all trace of residues present in the fresh
    olives.

         Normal domestic preparation and cooking of beans, cabbage,
    cauliflowers, peppers, tomatoes and chicory removes or destroys from
    60-100 percent of the dimethoate and omethoate present in the fresh
    commodity.

         Methods of residue analysis used to develop residue data over the
    30 years since dimethoate insecticides have been available have been
    reviewed. Some of these have obviously not recovered all of the
    omethoate that may have been present but methods recommended since
    about 1970 appear more satisfactory. The recommendations of the ad
    hoc. Working Group of the CCPR on methods suitable for regulatory
    purposes were confirmed.

         A number of countries have provided results of monitoring studies
    which indicate that the incidence of dimethoate and omethoate residues
    in foods in commerce is relatively low and that these residues are
    well within the recommended MRLs.

         Attention is drawn to the differences between the MRLs
    established in the legislation of many countries and the lack of
    harmony with the recommendations of the CCPR. The variation in
    preharvest intervals which apply in different countries could, in
    part, explain the differences in MRLs.

    RECOMMENDATIONS

         The Meeting, having considered extensive information on the
    occurence, level, nature and fate of residues resulting from the use
    of dimethoate and omethoate agreed that it was not possible to develop
    separate MRLs for dimethoate and omethoate bearing in mind that
    omethoate is frequently used on exactly the same commodities that are
    generally treated with dimethoate and in such cases the residues of
    omethoate are considerably higher than those from dimethoate.

         The MRLs previously recommended are confirmed.

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    See Also:
       Toxicological Abbreviations
       Dimethoate (EHC 90, 1989)
       Dimethoate (HSG 20, 1988)
       Dimethoate (ICSC)
       Dimethoate (PDS)
       Dimethoate (FAO Meeting Report PL/1965/10/1)
       Dimethoate (FAO/PL:CP/15)
       Dimethoate (FAO/PL:1967/M/11/1)
       Dimethoate (JMPR Evaluations 2003 Part II Toxicological)
       Dimethoate (AGP:1970/M/12/1)
       Dimethoate (Pesticide residues in food: 1983 evaluations)
       Dimethoate (Pesticide residues in food: 1984 evaluations)
       Dimethoate (Pesticide residues in food: 1987 evaluations Part II Toxicology)
       Dimethoate (Pesticide residues in food: 1996 evaluations Part II Toxicological)