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    METHOMYL      JMPR 1975

    IDENTITY

    Chemical name

         1-(methylthio)ethylideneamino methylcarbamate

    Synonyms

         S-methyl-N-[(methylcarbamoyl)oxy]thioacetimidate, LannateR,
         NudrinR, Dupont 1179

    Structural formula

                   O
                   "
         CH3-C=N-O-C -NH-CH3       C5H10N2O2S
             '
             S-CH3

    Other information on identity and properties

    Molecular weight: 162.2

    Physical state: white crystalline solid

    Melting point: 78-79C

    Specific gravity: 1.2946 25/4

    Odour: slightly sulfurous

    Vapour pressure:    5  10-5 mm Hg at 25C
                        1.6  10-4 mm Hg at 40C

    Solubility:    (grams/100 grams solvent):
                   water 5.8, methanol 100,
                   acetone 73, ethanol 42,
                   isopropanol 22, toluene 3.

    Stability

         Stable in solid form. Aqueous solutions in closed systems
    decompose slowly. Aeration, sunlight, alkalinity, and higher
    temperatures increase the rate of decomposition in water.

    Purity of technical material

         Technical methomyl contains a minimum of 95% methomyl, typically
    97-99%.

    RESIDUES IN FOOD AND THEIR EVALUATION

    USE PATTERN

         Methomyl, an insecticide with systemic properties, is toxic to
    insects both by direct contact and ingestion. It provides broad
    spectrum control of insects in many vegetables and field crops,
    certain fruit crops, and ornamentals (commercial plantings).

         Methomyl is effective against pests such as beetles, aphids,
    thrips, leaf hoppers and caterpillars and particularly loopers, beet
    armyworm and corn earworm (Harvey et al., 1973).

         The registered and recommended uses of methomyl in the United
    States of America are summarized in Table 1. Available information on
    the use patterns of methomyl in several other countries is summarized
    in Table 2.

         The use of methomyl in glasshouse tests against the greenhouse
    whitefly was reported by Krueger et al. (1973).

         Methomyl is marketed on a world-wide basis and products based on
    it are used in nearly 100 countries (du Pont de Nemours, 1975).
    Formulations produced include LannateR methomyl insecticide, a 90%
    active water-soluble powder, and LannateRL methomyl insecticide, a
    24% w/w water-miscible solution. A 25% wettable powder is used in
    Europe and in some other areas. A 45% water-soluble powder is favoured
    in Japan. Granules and dust formulations are used in certain areas.

    RESIDUES RESULTING FROM SUPERVISED TRIALS

         Residue data are available from supervised trials on a variety of
    fruits, vegetables and field crops (du Pont de Nemours, 1975). A
    summary of much of this information appears in Table 3, together with
    information on rates of application, number of applications and
    pre-harvest intervals used. These data are almost exclusively from the
    United States of America except for a few trials on wheat and barley
    from Canadian locations.

         Residue data from supervised trials in several other countries
    were reported to the Meeting. These are summarized in Table 4.
    Methomyl residues were detected on most above-ground crops at the time
    of harvest. Higher residues occurred on leafy vegetables, e.g.
    lettuce, spinach, celery and cabbage with generally low levels on root
    crops, cucurbits and grain crops. High residues were detected in
    alfalfa, pea, bean and peanut foliage and straw of wheat, oats and
    barley. The residue level diminishes with time after application. The
    amount of insecticide applied, time interval between last application
    and harvest, surface area, weight and surface structure of the crop
    are factors that affect the level of the residue. The amounts of
    residues resulting from the use of the powder and liquid formulations
    are nearly identical when an equal amount of active ingredient is
    applied (du Pont de Nemours, 1975).


    
    TABLE 1.  Registered and recommended uses of methomyl in the United States of America

                                                                                                                                       

                                                                                       Last application days
                                                                                                                To livestock
    Crops                     Insects                                  kg/ha        To harvest               grazing/feeding
                                                                                                                                       

    Alfalfa                   Beet Armyworm, Lygus Bugs                1/2-1                                    7

    Alfalfa -                 Beet Armyworm                            1/4-1/2
    Calif. & Ariz.            Alfalfa Caterpillar                      1/3-1/2                                  7
                              Aphids                                   1/2-1

    Beans (snap)              Leafhoppers
                              Mexican Bean Beetle                      1/4-1        1 for 1/4-1/2 kg/ha         3 (vines)
                              Beet Armyworm, Cabbage Looper,
                              Corn Earworm                             1/2-1        3 for 1/2-1 kg/ha           7 (hay)

    Broccoli, Cauliflower     Cabbage Looper, Imp. Cabbageworm,
                              Diamondback Moth                         1/4-1           3

    Brussels Sprouts          Cabbage Looper, Imp. Cabbageworm         1/2-1           3

    Cabbage                   Cabbage Looper, Imp. Cabbageworm,
                              Diamondback Moth                         1/4-1           1

    Celery                    Cabbage Looper                           1               14
                              Beet Armyworm                            1/2-1           14

    Citrus (oranges,          Citrus Thrip                             1/2-1           1                        10
    lemons, grapefruit,
    tangelos)

    Corn (sweet)              Earworm - Whorl as needed                1/3-1/2
                              Earworm - Ears 1-3 days or
                                             as needed                 1/4-1/2         0 (ears)              3 (forage)
                              Fall Armyworm, European Corn
                              Borer - Ears 1-3 days as needed          1/2

    TABLE 1.  (Cont'd.)

                                                                                                                                       

                                                                                       Last application days
                                                                                                                To livestock
    Crops                     Insects                                  kg/ha        To harvest               grazing/feeding
                                                                                                                                       

    Cotton                    Bollworm, Tobacco Budworm -
                              Do not apply more than                   1/2-3/4         15                    Do not graze or
                                             3 applications                                                  feed treated cotton

    Cucumber                  Cabbage Looper                           1/2-1           3

    Lettuce (head)            Cabbage & Alfalfa Loopers                1/4-1/2         7
                              Beet Armyworm                            1/2-1                                 10

    Melons                    Cabbage Looper                           1/2-1           3

    Nectarines                Thrips                                   1/2-1           1                     10

    Peanuts                   Corn Earworm, Beet Armyworm -
                              Up to 3 applications as needed           1/4-1           21                    Do not feed treated vines

    Peppers                   Green Peach Aphid                        1/2             10

    Potato                    Tuberworm, Cabbage Looper                1/2
                              Aphids                                   1/2-1
                              Leafhoppers )                                            14
                              Flea Beetles) East of Miss River         1/2

    Soybeans                  Soybean Looper, Green Cloverworm,
                              Mexican Bean Beetle, Corn
                              Earworm, Beet Armyworm,                  1/4-1/2         14                    3 (forage)
                              Velvetbean Caterpillar - Up to                                                 7 (hay)
                              2 applications

    TABLE 1.  (Cont'd.)

                                                                                                                                       

                                                                                       Last application days
                                                                                                                To livestock
    Crops                     Insects                                  kg/ha        To harvest               grazing/feeding
                                                                                                                                       

    Spinach                   Cabbage Looper, Beet Armyworm -
                              Do not apply when mininum daily
                              temperature is 32F or lower.            1/2-1           7
                              Do not apply to seedlings less
                              than 3" in diameter

    Squash (summer)           Cabbage Looper
                              Melonworm )                              1/2-1           3
                              Pickleworm) Southeast only

    Tomato                    Tomato Fruitworm, Aphids,                1/2             1
                              Cabbage Looper, Beet Armyworm            over 1/2-1      2

    Tobacco (except shade)    Flea Beetle, Hornworm                    1/4-1/2         7 (flue cured)
                              Budworm (2-3 applications before
                              flower buds open), Cabbage               1/2             14 (air or fire cured)
                              Looper, Aphids

    Chrysanthemums            Cabbage Looper, Corn Earworm,            1/4-1/2 lb
                              Beet Armyworm, Thrips (weekly)           per 100 gals.
                                                                                                                                       

    TABLE 2.  Use patterns of methomyl in some countries other than the United States of America

                                                                                                                                          

                                                                                                                             Pre-harvest
                                                                                     Application        No. of               interval
    Country        Crop                                             Formulation          rate           applications            (days)
                                                                                                                                          

    Australia      beans                                          22.5% water        100 ml/100       4 (bean fly), as            1
                                                                  miscible liquid    litres           necessary (been
                                                                                                      thrips)
                   leafy vegetables - cauliflower, broccoli,                             "            as necessary -
                   cabbage                                                                            5-14 day intervals          3

                   peaches, nectarines                                                   "            as necessary                1

                   tobacco                                                               "            as necessary                -

    Canada         lettuce                                        21.6% water        0.4-0.8 kg/ha    as necessary -              7
                   broccoli, Brussels sprouts, cauliflower,       soluble liquid     0.25-0.5 kg/ha   5-7 day intervals
                   cabbage                                        (maximum limit                             "                    7, 1
                                                                  of active                                                     (cabbage)
                   rutabaga                                       ingredient         0.9 kg/ha               1                    14
                   pea                                            content of 34%)    0.5 kg/ha        as necessary -              1
                                                                                                      5-7 day intervals
                   potato                                                                "                   "                    3

                   tomato                                                            0.25-0.5 kg/ha          "                    1

                   corn (sweet and field)                                                "            as necessary -              3
                                                                                                      2-5 day intervals

                   rapeseed                                                          0.2-0.3 kg/ha                                8

                   flax                                                              0.25-0.3 kg/ha                               30

    Malaysia       vegetables, tobacco, soybeans, rice, maize,    90% water          0.25-0.5 kg/ha   as necessary -              7
                   grapes, tomatoes, citrus, lichee               soluble powder                      5-7 day intervals

    TABLE 2.  (Cont'd.)

                                                                                                                                          

                                                                                                                             Pre-harvest
                                                                                     Application        No. of               interval
    Country        Crop                                             Formulation          rate           applications            (days)
                                                                                                                                          

    Mexico         cotton, tobacco, potato, tomato, maize,        90% water          0.25-0.4 kg/ha
                   sorghum, safflower, alfalfa, soybean,          soluble powder
                   peppers, broccoli, cabbage, cauliflower,
                   lettuce, cucumbers, melons, pumpkins, beans

    Netherlands    tomatoes, peppers (glasshouse)                 25% water                                                       3
                                                                  soluble powder

    New Zealand    cereals, pasture, maize, lettuce, brassicas,   90% water          0.27-0.36 kg/ha                              7
                   tobacco                                        soluble powder

                   tomatoes, beans                                                         "                                      7

                   canefruit                                                         0.022 kg/100                                 2
                                                                                     litres

                   grapes                                                            0.022-0.36 kg/                                                                               7
                                                                                     100 litres

    Central        Cotton, rice, okra, citrus, peppers, beans,    90% water          0.25-0.5 kg/ha                               1-7
    America        leafy vegetables, maize, peanuts, potatoes,    soluble powder
                   tomatoes, sorghum, soybeans, tobacco,
                   ornamental plants

    France         grapes, fruits, vegetables, ornamentals        25% wettable       125-200 g/100    as necessary
                                                                  powder             litres

    Germany,       leafy vegetables except cabbage, root          25% wettable       100-150 g/100                              14, 21
    Federal        vegetables                                     powder             litres                                  (glasshouse)
    Republic of                                                                                                                 7, 14
                   cabbage, onion                                                                                            (glasshouse)

    TABLE 2.  (Cont'd.)

                                                                                                                                          

                                                                                                                             Pre-harvest
                                                                                     Application        No. of               interval
    Country        Crop                                             Formulation          rate           applications            (days)
                                                                                                                                          

                   leek                                                                                                           14

                   fruits except cucumbers, tomatoes                                                                            7, 10
                                                                                                                             (glasshouse)
                   cucumber, tomatoes                                                                                             3

                   hops                                                                                                           14

                   grapes                                                                                                         28

    Japan,         rice                                             45% wettable     0.45-0.75 kg/ha    3                         21
    Far East       cabbage                                          powder                 "            3                         3

                   tea                                                                     "            2                         20

                   tobacco                                                                 "            -                         -

                   chinese cabbage                                                         "            2                         14

                   radish                                                            0.6-0.9 kg/ha      3                         7

                   pepper                                                            0.45-0.75 kg/ha    4                         7

                   sweet potato, sugarbeet                                                 "            5                         7

    South          citrus                                           90% water        0.02-0.03 kg/ha                         2 (>0.02 kg/
    Africa                                                          soluble powder                                           100 litres)
                                                                                                                             28 (>0.02 kg/
                                                                                                                             100 litres)

    TABLE 2.  (Cont'd.)

                                                                                                                                          

                                                                                                                             Pre-harvest
                                                                                     Application        No. of               interval
    Country        Crop                                             Formulation          rate           applications            (days)
                                                                                                                                          

                   peaches                                                           0.05 kg/100
                                                                                     litres                                       16

                   sorghum, maize                                                    0.165 kg/ha                                  7

                   tobacco                                                           0.225 kg/ha                             7 (ovendried)
                                                                                                                             14 (airdried)

                   tomatoes                                                          0.05 kg/100                                  2
                                                                                     litres

                   potatoes                                                          0.33-0.45 kg/ha                              3

                   green beans                                                       0.225 kg/ha        3                         3

                   cauliflower, cabbage                                              0.025-0.05 kg/                               4
                                                                                     100 litres

    Spain          tomatoes, citrus fruits, olives, cotton,         25% wettable     0.125-0.2 kg/                                7
                   sugarbeet, tobacco, ornamentals                  powder           100 litres

    United         hops                                             25% wettable     0.25-0.8 kg/ha   as necessary -
    Kingdom                                                         powder                            1-12 day Intervals
                                                                                                                                          
    

         Methomyl residues were not detected in rape seeds (limit of
    detection 0.03 mg/kg) harvested 19-28 days after spraying at the rate
    of 0.21-0.28 kg/ha (Mendoza et al., 1974). Six trials were carried out
    at different locations. Methomyl residues in rapeseed pods decreased
    from 9.06 mg/kg one day after spraying at the rate of 0.25 kg/ha to
    2.3 mg/kg on day 14 (Cochrane, 1975).

         The residual behaviour of methomyl in peppermint and spearmint
    hay and oil is summarized in Table 5 (Kiigemagi et al., 1973).
    Residues of methomyl were not detected in the oil even at hay residues
    as high as 3.54 mg/kg.

         Methomyl residues determined on flue-cured and cigar-wrapper
    tobaccos are shown in Table 6 (Tappan et al., 1973). Residues were
    higher on cigar-wrapper than on flue-cured tobacco. There appeared to
    be only minimal loss of residue from cigar-wrapper tobacco because of
    relatively low temperatures during the curing and fermentation
    processes. In one experiment (du Pont de Nemours, 1975) residues in
    green tobacco harvested 1, 3 and 7 days after last treatment with
    methomyl were 9.6, 10.0 and 0.92 mg/kg, respectively. After flue
    curing the residues were 3.8, 2.9 and 0.52 mg/kg representing a 44-72%
    reduction in methomyl residues.

         Glasshouse trials on tomatoes were reported (Krueger et al.,
    1973) and the data are shown in Table 7. Residues were higher and more
    persistent than the field trials reported in Tables 3 and 4.

         Residues of methomyl were not detected in milk from two cows fed
    the compound at 2 and 20 mg/kg in the ration for 30 days (du Pont de
    Nemours, 1975). Samples were collected and analysed every two days
    during the experimental period. At the end of the 30 day period the
    cows were killed. Residues of methomyl were not detected in samples of
    lean muscle, subcutaneous fat, liver or kidney. The method was
    sensitive to 0.02 mg/kg.

         Aerial spraying of rape fields with methomyl (0.25 kg/ha)
    resulted in the death of bees (Greenhalgh, 1975). Dead bees were
    collected 1.5, 3 and 24 hours after spraying. Methomyl residues were
    2.03, 0.46 and 0.65 mg/kg, respectively. Dead bees (3 hours after
    spraying) from an individual hive contained 0.42 mg/kg methomyl.
    Samples of nectar, collected from this hive 8 to 10 hours after
    spraying, did not contain detectable methomyl residues. Two samples of
    dead bees were stored for one year at 0 and reanalysed. Residue
    levels had dropped from 2.03 and 0.65 mg/kg to 0.4 and 0.04 mg/kg,
    respectively.

         Soil studies indicated the loss of 50-75% of applied methomyl
    after 30 days, with only trace quantities remaining after 90 days and
    no detectable residue within one year (du Pont de Nemours, 1975;
    Harvey & Pease, 1973).


    
    TABLE 3.  Methomyl residues in crops from supervised trials in the United States of America

                                                                                                                                               

                                                                              Residues (mg/kg)1

                                                                              Pre-harvest interval in days
                  Rate      No. of
        Crop      kg/ha     applications     0-1                2-3                4-7              8-10               11-14               >14
                                                                                                                                               

    Cabbage       0.25-0.38     6-10     0.03-0.40 (2)    <0.02-0.35 (3)    <02-0.02 (2)                       <0.02 (2)
                  0.5           1-8      0.04-3.0 (9)     <0.02-0.44 (7)    <0.02-0.16 (9)   <0.02-0.15 (4)    <0.02-0.02 (3)     <0.02 (2)
                  1.0           1-7      0.15-16 (7)      0.16-1.1 (4)      <0.02-0.92 (5)   <0.02-0.56 (4)    <0.02-0.02 (2)     <0.02 (2)

    Lettuce,      0.25          2-3      6.2 (1)          <0.02-5.7 (3)     <0.02-3.6 (6)    <0.02 (1)         <0.02-0.60 (4)
        head      0.45-0.5      3-6      0.80-17 (7)      0.06-17 (12)      <0.02-7.1 (23)   0.06-1.6 (5)      <0.02-0.68 (12)    <0.02 (1)
                  0.9-1.0       3-5      10-40 (3)        0.07-19 (8)       <0.02-15 (15)    0.60-0.88 (2)     <0.02-1.4 (7)      <0.02 (1)
                  1.8           4                         48 (1)            3.6 (1)          3.2 (1)           2.5 (1)

    Lettuce,      0.25          3                         2.0 (1)           0.52-1.3 (2)                       0.02 (1)
        leaf      0.50          3                         9.2 (1)           1.0-9.2 (2)                        0.48 (1)
                  1.0           3                         34 (1)            4.2-29 (2)                         0.76 (1)

    Spinach       0.3-0.6       1-7      8.8-32 (3)       1.7-7.4 (7)       0.07-6.9 (15)    0.04-1.2 (3)      <0.02-0.13 (5)     0.60 (1)
                  0.9-1.2       1-9      0.06-96 (4)      0.51-16 (11)      0.07-5.7 (14)    0.22-1.3 (3)      0.03-0.13 (5)      0.56 (1)

    Tomatoes      0.25          4-5      0.02 (2)         <0.02 (1)         <0.02 (2)        <0.02 (2)         <0.02 (1)
                  0.45-0.5      3-16     0.03-0.24 (6)    <0.02-0.09 (8)    <0.02-0.04 (16)  <0.02 (4)         <0.02 (1)
                  0.9-1.0       1-8      <0.02-1.34 (16)  <0.02-0.13 (10)   <0.02-0.04 (5)
                  1.8-2.0       5-8      0.37 (1)         <0.02 (1)         <0.02 (1)

    Peppers       0.45-0.67     1-9      0.06-0.34 (6)    0.02-0.39 (10)    0.02-0.38 (9)    0.05-0.07 (2)
                  0.9-1.0       1-8      0.11-3.2 (12)    0.03-0.44 (12)    0.03-0.74 (7)    0.03-0.10 (3)     0.19-0.24 (2)
                  1.8-2.0       1-8      0.43-2.2 (2)     0.15-0.46 (2)     0.44 (1)         0.19 (1)

    Eggplants     0.5           2-9                       0.05-0.10 (3)     <0.02-0.11 (5)   0.02 (1)
                  1.0           6                         0.30 (1)          0.11 (1)         0.15 (1)

    TABLE 3.  (Cont'd.)

                                                                                                                                               

                                                                              Residues (mg/kg)1

                                                                              Pre-harvest interval in days
                  Rate      No. of
        Crop      kg/ha     applications     0-1                2-3                4-7              8-10               11-14               >14
                                                                                                                                               

    Cucumber      0.5-0.75      2-8      0.03-0.07 (2)     0.04-0.07 (3)      0.02 (1)
                  1.0           6-8      0.04 (1)          <0.02 (1)          0.04 (1)

    Squash,       0.5           1        0.03 (1)          0.02 (1)           <0.02 (1)
        summer    1.0           1        0.07 (1)          0.05 (1)           <0.02 (1)

    Cantaloupe    0.5-0.75      1-8                        0.02-0.17 (4)      0.03-0.07 (3)
                  1.0           3-8                        0.10-0.12 (3)      0.09-0.16 (3)

    Melons -      0.5-1.0       1-2      0.03-0.15 (3)     <0.02 (3)          <0.02-0.09 (2)
        honeydew,
        crenshaw,
        casaba

    Watermelon    0.5-1.0       1-7                        <0.02-0.07 (6)     <0.02 (4)                           <0.02 (1)

    Asparagus     0.45-0.5      1-5      <0.04-0.76 (11)   <0.02-0.21 (11)    <0.04 (4)
                  0.9-1.0       1-5      <0.04-1.1 (19)    <0.02-0.52 (15)    <0.02-0.12 (8)                      <0.02 (4)

                  1.8           2-5      0.26-2.5 (8)      0.07-0.17 (4)

    Celery        0.45          1-6      4.6-7.4 (12)      0.09-2.7 (6)       <0.02-1.4 (6)    <0.02 (1)          <0.02-0.06 (14)
                  0.75-0.9      1-11     1.6-22 (2)        0.25-6.9 (8)       <0.02-3.7 (11)   <0.02-0.13 (3)     <0.02-0.17 (11)
                  1.5-1.8       3-11     2.9 (1)           0.64-7.4 (3)       0.28-4.3 (3)     0.14 (1)

    TABLE 3.  (Cont'd.)

                                                                                                                                               

                                                                              Residues (mg/kg)1

                                                                              Pre-harvest interval in days
                  Rate      No. of
        Crop      kg/ha     applications     0-1                2-3                4-7              8-10               11-14               >14
                                                                                                                                               

    Sweet corn    0.25-0.5      2-12     <0.02-0.03 (9)   <0.02 (5)         <0.02 (3)                           <0.02 (2)
                  0.75-1.5      2-14     <0.02-0.03 (3)   <0.02-0.07 (6)    0.03 (1)          <0.02-0.02 (2)

    Potatoes      0.04-0.6      3-10                      <0.02 (1)         <0.02 (1)                                               <0.02 (5)
                  1.0-10        1-7                       <0.02 (1)                                                                 <0.02 (6)

    Onions,       0.25-0.5      1-2                                         <0.02-0.28 (5)    0.36 (1)          <0.02-0.11 (7)      <0.02-
        green                                                                                                                       0.28 (12)
                  0.9-1.8       1-2                                                                             <0.02-0.26 (4)

    Onions, dry   0.45-0.9      1-4      0.05-0.08 (2)                      <0.02-0.06 (5)                      <0.02-0.1 (4)       <0.02 (3)

    Sugarbeets -  0.5-1.0       1-3                                         <0.02 (4)                           <0.02 (2)          <0.02 (7)
        roots     4-12          1-4                                         <0.02 (2)                                              <0.02 (4)

    Sugarbeets -  0.5-1.0       1-3                                         0.72-2.1 (4)                        <0.02-0.84 (6)     <0.02 (7)
        tops      4-12          1-4                                         2.8-5.7 (2)                         0.12 (1)           <0.02-
                                                                                                                                   1.4 (5)

    Peas, green   0.45-0.5      1-3      <0.02-0.12 (3)                     <0.02 (1)
                  0.9-1.0       1-3      0.09-0.52 (3)                      <0.02 (1)
                  2.0           1-2      1.1 (1)                                                                <0.02 (1)          <0.02 (1)

    Peas, green-  0.45-0.5      1-3      0.06-4.0 (5)      0.07-1.1 (4)     <0.02-0.17 (5)                      <0.02 (1)
    filled pods   0.9-1.0       1-3      0.20-4.6 (6)      0.19-1.4 (6)     0.04-0.27 (5)
                  2.0           1-2      2.2 (1)           0.64-0.93 (2)                                        <0.02 (1)          0.02 (1)

    Peas, green-  0.45-0.5      1-3      1.3-15 (5)        0.11-5.8 (2)     <0.02-3.1 (6)                       0.02 (1)
        forage    0.9-1.0       1-3      4.2-33 (5)        3.7-4.3 (2)      0.12-7.6 (6)
                  2.0           1-2      27-48 (2)                            10-14 (2)                         0.06-4.9 (2)        0.30 (1)

    TABLE 3.  (Cont'd.)

                                                                                                                                               

                                                                              Residues (mg/kg)1

                                                                              Pre-harvest interval in days
                  Rate      No. of
        Crop      kg/ha     applications     0-1                2-3                4-7              8-10               11-14               >14
                                                                                                                                               

    Snap beans    0.2-0.5       2-7      <0.02-1.0 (4)    <0.02-0.30 (9)    <0.02-0.44 (10)                     <0.02 (1)
                  1.0           2-6      0.06-1.4 (3)     0.03-0.30 (3)     <0.02-0.62 (5)

    Lima beans    0.5-1.0       6-11                      0.68 (1)          <0.02-0.05 (2)        0.03 (1)

    Dry beans     0.45-0.5      1-2      <0.02 (4)                          <0.02 (9)                           <0.02 (1)
                  0.9-1.0       1        <0.02 (4)        <0.02 (6)         <0.02 (9)                           <0.02 (4)          <0.02 (1)

    Soybeans      0.5-1.0       1-4                                                                             <0.02 (2)          <0.02 (13)
                  2.0-4.0       1-4                                                                                                <0.02 (2)

    Soybean       0.5           1-4      0.60 (1)         <0.02-5.1 (5)     0.03-0.80 (3)         0.12 (1)      0.07-0.15 (2)
        forage    1.0-2.0       1-4                       0.02-8.0 (4)      3.7 (1)               0.88 (1)      0.08-0.40 (3)

    Peanuts       0.45-1.8      1-4                                         <0.02 (2)             <0.02 (1)                        <0.02 (4)

    Peanut hulls  0.45-1.8      1-4                                         <0.02 (2)             <0.02 (1)                        <0.02 (4)

    Peanut        0.45-0.5      1-4      20 (1)            14 (1)           <0.02-1.8 (2)         0.43 (1)      <0.02 (1)          <0.02-
        foliage                                                                                                                    0.34 (7)
                  0.9-1.0       1-4      13-48 (5)         7.1-31 (5)       1.3-20 (6)            1.4 (1)       0.23 (1)           0.04-
                                                                                                                                   0.99 (8)
                  1.8-2.0       3        >100 (1)          48 (1)           16 (1)                                                 0.14-
                                                                                                                                   3.8 (2)

    Cottonseed    0.25-0.5      2-9                        2.1-2.2 (2)                            <0.02 (3)                        <0.02 (6)
                  1.0-2.0       1-9                        0.1 (1)                                <0.02 (2)                        <0.02-
                                                                                                                                   0.21 (8)

    TABLE 3.  (Cont'd.)

                                                                                                                                               

                                                                              Residues (mg/kg)1

                                                                              Pre-harvest interval in days
                  Rate      No. of
        Crop      kg/ha     applications     0-1                2-3                4-7              8-10               11-14               >14
                                                                                                                                               

    Wheat         0.22-0.5      1-7      <0.02-0.09 (7)   <0.02-0.07 (8)      <0.02-0.30 (10)    <0.02-0.12 (2)    0.09 (1)
                  0.9-1.0       2-5      0.17-0.21 (2)                        0.24-0.33 (2)                        0.02 (1)

    Wheat, green  0.45-0.5      2        22-48 (2)        12-18 (2)           0.12-4.9 (7)       0.37-0.59 (2)     0.03-0.16 (6)
        forage    0.9-1.0       2-4      36-46 (2)        30-34 (2)           0.32-12 (5)                          0.12-0.34 (3)

    Wheat straw   0.22-0.5      1-5      23-26 (2)        0.90-20 (3)         0.07-11 (10)       2.0-4.0 (2)       0.09-0.16 (2)       1.0-2.7 (2)
                  0.9-1.0       4-5      34-55 (2)                            1.8-15 (3)                           0.08 (1)

    Barley        0.22-0.45     1-4                                           <0.02-0.72 (5)                       <0.02-0.21 (4)      <0.02 (1)
                  0.9           4                                             0.14-1.11 (2)                        <0.02-0.04 (2)

    Barley,       0.45          2                         14-16 (2)           11 (1)                               0.02-0.15 (2)
    green forage  0.9           2                         38-45 (2)           14-18 (2)                            0.06-0.47 (2)

    Barley straw  0.22-0.45     1-4                                           0.05-3.1 (5)                         <0.02-0.28 (4)      <0.05 (1)
                  0.9           4                                             4.8-6.8 (2)                          <0.02-0.16 (2)

    Oats          0.45-0.9      4                                                                                  <0.02 (4)

    Oats, green   0.45-0.9      2                                                                                  0.05-0.27 (4)
        forage

    Oats straw    0.45-0.9      4                                             1.7-7.1 (4)                          <0.05 (4)

    Sorghum       0.33-0.5      1                                             0.09 (2)                                                <0.02-
                                                                                                                                      0.07 (7)
                  0.75-2.0      1-2                       0.36 (1)                                                 <0.02-0.08 (4)     <0.02 (5)

    TABLE 3.  (Cont'd.)

                                                                                                                                               

                                                                              Residues (mg/kg)1

                                                                              Pre-harvest interval in days
                  Rate      No. of
        Crop      kg/ha     applications     0-1                2-3                4-7              8-10               11-14               >14
                                                                                                                                               

    Sorghum       0.33-0.5      1                                             0.56-1.4 (2)                                             <0.05-
    foliage                                                                                                                            0.59 (7)
                  0.75-2.0      1-2                            1.8 (1)                                             0.12-0.38 (2)       <0.05 (6)

    Apples        0.75-1.0      5-9      0.43-3.2 (5)      0.22-1.7 (2)       0.07-0.6 (4)      0.21-0.32 (2)      0.06 (1)            <0.02-
                                                                                                                                       0.12 (8)
                  1.5           8        8.7-9.7 (2)       4.2-5.1 (2)        0.68-1.2 (2)      0.31-0.52 (2)
                  2.0-2.5       5-12     0.12-0.64 (2)                                                             <0.02-0.06 (2)      0.32-
                                                                                                                                       0.72 (4)

    Peach         0.5           7-8      5.6-6.9 (2)                          1.1-4.0 (2)       0.69-3.1 (2)

    Nectarine     0.5           1        0.21-0.70 (2)
                  1.0           1        0.36-4.1 (2)                         0.49 (1)          0.17 (1)                               <0.02 (1)
                  2.0           1        1.5-13.5 (2)                         0.08 (1)          0.07 (1)

    Grapes        0.33-0.67     1-2      0.04-0.28 (4)     <0.02 (1)         <0.02-0.40 (7)    <0.02 (1)                               <0.02 (1)
                  1.0-2.0       1-2      0.4-4.2 (8)       0.11-1.7 (8)      0.22-2.1 (9)      0.24-0.60 (3)                           0.14 (1)

    Pineapple     2.5-5.0       6                                                                                                      <0.02 (2)
                  10-20         1-6                                                                                                    <0.02-
                                                                                                                                       0.10 (11)

    Grapefruit    0.5-1.0       1                          0.25-0.33 (2)     0.02-0.07 (2)

    Oranges       0.75-1.5      1-5      0.16-0.70 (4)     0.05-0.07 (3)     <0.02-0.07 (6)    0.02-0.04 (2)
                  2.0-4.0       1        0.28 (1)          0.13-1.6 (2)      0.05 (1)

    Lemon         1.0-4.0       1        <0.02-0.22 (4)    0.04-0.18 (3)     <0.02 (3)         <0.02 (1)

    TABLE 3.  (Cont'd.)

                                                                                                                                               

                                                                              Residues (mg/kg)1

                                                                              Pre-harvest interval in days
                  Rate      No. of
        Crop      kg/ha     applications     0-1                2-3                4-7              8-10               11-14               >14
                                                                                                                                               

    Tangelos      1.0           5        1.7 (1)           1.0 (1)            0.16 (1)          0.06 (1)

    Alfalfa       0.25-0.5      1        7.8-20 (3)        2.0-6.5 (5)        0.30-10 (11)                         0.20-0.78 (3)
                  1.0-2.0       1        18-100 (2)        26-62 (3)          1.5-6.8 (7)                          0.87-2.3 (2)

    Tobacco       0.5-1.0       2-4      9.1-16 (3)        0.39-10 (4)        0.02-0.92 (3)     0.24 (1)                               <0.02 (1)
        (green)   12            1                                                                                                      0.06 (1)
                  8-16 mg/      1                                                                                                      <0.02 (2)
                  plant

    Tobacco       0.25-1.0      2-5      0.60-6.5 (7)      2.8 (1)            0.07-0.52 (6)     0.17 (1)           0.03-0.11 (4)       <0.02-
                                                                                                                                       0.10 (3)
    (flue cured)  4.0           4        31 (1)                               0.29 (1)                             0.09 (1)
                  12-24         1                                                                                                      <0.02-
                                                                                                                                       0.19 (5)
                  6-12 mg/      1                                                                                                      <0.02 (3)
                  plant

    1  Residues, mg/kg, at interval, days, after application. (Number of samples in parenthesis.)
                                                                                                                                               

    TABLE 4.  Methomyl residues in crops from supervised trials from various countries

                                                                                                                                               

                                        Application               Residues in mg/kg, at intervals (days) after application1
                                        Rate kg
    Crop            Country       No.   a.i./ha      Formulation  0-1           2-3           4-7           8-10          11-14       >14
                                                                                                                                               

    Tomatoes        Germany       1     0.225        25% wp       <0.01 (1)     0.02 (1)      <0.01-        <0.01 (1)     <0.01 (1)
                    South Africa  6-10  0.05         90% WP       <0.02-                      0.02 (2)
                                                                  0.13 (4)      <0.02 (2)

    Tomatoes        Germany       1     0.225        25% WP       0.19 (1)      0.07 (1)      0.02-         0.02 (1)      0.05 (1)
    (glasshouse)    Netherlands   1     0.075        25% WP       0.01-         <0.01-        0.07 (2)
                                                                  0.02 (2)      0.02 (2)
                                  2     0.125                     0.05-         0.02-
                                                                  0.06 (2)      0.03 (2)
                    New Zealand   1     0.28         90% WP       <0.01-        <0.01-        <0.01 (2)     <0.01 (1)
                                                                  0.08 (2)      0.02 (3)
                                  1     0.56                      0.04-         <0.01-        <0.01-        <0.01 (1)
                                                                  0.11 (2)      0.06 (3)      0.02 (2)
                                  1     1.12                      0.3 (1)       0.06-         0.05 (1)
                                                                                0.13 (2)

    Cabbage         Germany       1     0.225        25% WP       0.38 (1)      0.02 (1)      0.01-         0.01 (1)      <0.01 (1)
                    South Africa  1     45g/100l     90% WP       1.8-1.9 (2)   0.21 (1)      0.02 (2)      0.08 (1)                  0.05 (1)
                    Far East      2-6   0.675        45% WP                                   0.21-                       0.21-
                                                                                              0.80 (4)                    0.33 (4)

    Cauliflower     Germany       1     0.225        25% WP       0.94 (1)      0.06 (1)      0.03-         0.01 (1)      <0.01 (1)
                                                                                              0.04 (2)
                    South Africa  1     90g/100l     90% WP       0.62 (1)      0.95 (1)      0.23 (1)      0.05 (1)                  0.06 (1)

    Beans           New Zealand   1     0.4-0.8      90% WP       0.10-         0.01-         <0.01-
                                                                  0.15 (2)      0.17 (4)      0.01 (4)
                    South Africa  3     0.225        90% WP       0.06-         0.03 (1)      <0.03 (1)
                                                                  0.69 (2)

    TABLE 4.  (Cont'd.)

                                                                                                                                               

                                        Application               Residues in mg/kg, at intervals (days) after application1
                                        Rate kg
    Crop            Country       No.   a.i./ha      Formulation  0-1           2-3           4-7           8-10          11-14       >14
                                                                                                                                               

    Peaches         South Africa  3     45g/100l     90% WP       2.0-          2.1 (1)       1.2 (1)       0.46-                     <0.1-
                                                                  3.9 (2)                                   0.5 (2)                   0.12 (2)

    Carrots         Germany       1     0.225        23% WP       0.09 (1)      <0.02 (1)     <0.02 (2)     <0.02 (1)     <0.02 (1)

    Onions          Germany       1     0.225        25% WP       <0.01 (1)     0.01 (1)      0.02-         <0.01 (1)     <0.01 (1)
                                                                                              0.08 (2)
                    Far East      2-4   0.675        45% WP       <0.01 (2)     <0.01 (2)     <0.01 (2)     <0.01 (2)

    Potatoes        South Africa  10    0.45         90% WP                     <0.02 (1)

    Sweet potatoes  Far East      3-5   0.63         45% WP                                   <0.01 (4)                   <0.01 (2)   <0.01 (2)

    Radish          Germany       1     0.225        25% WP       0.46 (1)      0.16 (1)      0.08-         0.08 (1)      0.08 (1)
                                                                                              0.20 (2)

    Radish          Germany       1     0.225        25% WP       0.14 (1)      0.78 (1)      0.81-         1.06 (1)      0.22 (1)
    (glasshouse)                                                                              0.98 (2)

    Horse radish    Far East      2-3   0.45         45% WP       0.06-         0.07 (1)      0.11-         0.16-         0.16-       0.17-
                                                                  0.07 (2)                    0.18 (2)      0.22 (2)      0.21 (2)    0.23 (2)

    Peppers         Far East      4-6   0.36         45% WP       0.51-                       0.05-                       0.01-
                                                                  2.5 (4)                     0.69 (4)                    0.20 (4)

    Grapes          New Zealand   1     25-50g/100l  90% WP       1.01-         0.49-         0.05-                       0.05 (4)
                                                                  2.14 (4)      0.94 (4)      0.12 (4)

    Apples          Denmark       1     1.25         25% WP       1.92-                                     1.18-                     0.96-
                                                                  2.08 (2)                                  1.96 (2)                  1.56 (4)

    TABLE 4.  (Cont'd.)

                                                                                                                                               

                                        Application               Residues in mg/kg, at intervals (days) after application1
                                        Rate kg
    Crop            Country       No.   a.i./ha      Formulation  0-1           2-3           4-7           8-10          11-14       >14
                                                                                                                                               

    Cucumbers       Denmark       1     0.25g/plant  25% WP       0.73-                       0.11-         0.07-
                                                                  0.97 (4)                    0.46 (4)      0.14 (2)
    (glasshouse)    Germany       1     0.225        25% WP       0.15 (1)      <0.01 (1)     0.02 (2)      <0.01 (1)     <0.01 (1)

    Cucumbers       Germany       1     0.225        25% WP       0.05 (1)      0.04 (1)      <0.01 (2)     <0.01 (1)     <0.01 (1)

    Oranges         South Africa  1     18g/100l     90% WP       0.22-         0.03 (1)      <0.02-        <0.02 (1)
                                                                  0.42 (2)                    0.03 (3)
                                  1     50g/100l                  1.8 (1)       0.63 (1)      0.58 (1)      0.27 (1)                  0.37 (1)

    Blackcurrants   Denmark       4     0.75         25% WP                                                               1.06-       0.06-
                                                                                                                          1.20 (2)    0.23 (8)

    Strawberries    Denmark       1     0.5          25% WP                                                                           <0.05 (8)

    Raspberries     New Zealand   1     22-45g/100l  90% WP       0.06-         0.01-         <0.01 (2)
                                                                  0.15 (2)      0.02 (2)

    Spinach         Germany       1     0.225        25% WP       9.06 (1)      0.86 (1)      0.16-         0.01 (1)      0.02 (1)
                                                                                              0.91 (2)

    Lettuce         Germany       1     0.225        25% wp       2.59 (1)      0.30 (1)      0.02-         <0.01 (1)     <0.01 (1)
                                                                                              0.08 (2)

    Lettuce         Germany       1     0.225        25% WP       3.20 (1)      2.73 (1)      1.80-         1.24 (1)      0.29 (1)
    (glasshouse)                                                                              2.28 (2)

    Sorghum         South Africa  1     0.33         90% WP       1.9-                        <0.04 (2)                   <0.04 (2)
                                                                  2.25 (2)

    Maize           South Africa  1     0.16         90% WP       <0.02 (1)     <0.02 (1)

    TABLE 4.  (Cont'd.)

                                                                                                                                               

                                        Application               Residues in mg/kg, at intervals (days) after application1
                                        Rate kg
    Crop            Country       No.   a.i./ha      Formulation  0-1           2-3           4-7           8-10          11-14       >14
                                                                                                                                               

    Rice            Far East      1-3   0.675        45% WP                                                                           <0.01 (5)

    Tea             Far East      1-2   0.81         45% wp                                   0.08-                       0.04-       <0.01 (4)
                                                                                              0.40 (5)                    0.33 (5)

    Tobacco         South Africa  4     0.225        45% WP       0.05 (1)
                    Far East      1     0.34-0.67    45% wp                                                                           <0.01-
                                                                                                                                      0.02 (6)
                    Turkey        1-3   0.25                                                                0.15 (1)      0.49 (1)    0.51 (1)

    Hops (dried)    Germany       3-4   0.125-0.25   25% WP                                                               <0.02 (3)   0.02 (5)
                    United        5-9   0.06-0.10    20, 25%                                  <0.02-                                  <0.02 (1)
                     Kingdom                         water                                    0.20 (6)
                                                     soluble
                                                     liquid,
                                                     25% WP
                                  4-6   0.125                                                 <0.02-
                                                                                              0.96(4)
                                  4-5   0.15-0.19                                             0.31-
                                                                                              1.20 (3)
                                                                                                                                               

    1  Numbers in parenthesis are the number of samples.
    

        TABLE 5.  Methomyl residues in mint in supervised trials (Kiigemagi et al., 1973)

                                                                                                 

    Rate            No. of          Pre-harvest            Methomyl residues (mg/kg) in
    kg/ha        applications       interval (days)    fresh hay        spent hay       oil
                                                                                                 

                                    Peppermint

    0.28            1                  13              0.09             <0.02          <0.04

    0.56            1-2                0               2.13-10.1
                                       3               1.53
                                       7               <0.02-0.66
                                       8               0.39             0.29            <0.04
                                       14-26           <0.02-0.12      <0.02-0.08      <0.04

    1.1             1-2                0               4.20-20.6
                                       3               1.06-2.56
                                       7               0.02-1.19
                                       8               0.55             0.36            0.04
                                       14-26           <0.02-0.17      <0.02-0.13     <0.04

    2.2             1                  0               28.0
                                       3               1.64
                                       7               0.55
                                       26              0.22             0.03            <0.04

                                    Spearmint

    0.56            1-2                0               56.7
                                       7               3.75
                                       8               3.59             0.28            <0.04
                                       14-22           0.23-1.51        0.11-0.12       <0.04

    1.1             1-2                0               133
                                       7               7.50
                                       8               5.34             0.34            <0.04
                                       14              0.16             0.17            <0.04
                                                                                                 
    
    TABLE 6.  Methomyl residues on cigar-wrapper and flue-cured tobaccos
              (Tappan et al., 1973)

                                                                             

    Rate                No. of                Pre-harvest       Residues
    kg/ha             applications          interval (days)     (mg/kg)
                                                                             

                           Cigar-wrapper tobacco

    0.95-1.1               3-6                 0                22.17-100.3
    1.17-1.04              4                   1                30.2
    1.07-0.95              6                   7                8.36
    1.07                   6                   14               3.87

                           Flue-cured tobacco

    0.33-0.34              4-7                 5                0.03-0.25
    0.34                   7                   12               0.03
    0.34                   6                   13               0.03
    0.34                   7                   19               <0.02
                                                                             


    TABLE 7.  Methomyl residues in glasshouse tomatoes (Krueger et al., 1973)

                                                                             

                                  Methomyl (mg/kg)1 at dosages of

    Days after treatment          0.03 kg/ha         0.06 kg/ha
                                                                             

         1st spray
         0.5                           0.61            0.99
         1.5                           0.22            0.77
         3                             0.20            0.71
         6                             0.11            0.53

         2nd spray

         0.5                           0.97            2.11
         7                             0.18            0.65

         3rd spray

         7                             0.35            0.59
                                                                             

    1  Mean of 3 replicate experiments.

    FATE OF RESIDUES

    General comments

         The metabolism of methomyl in plants and rats results in the
    rapid complete degradation of the molecule to carbon dioxide and
    acetonitrile as the major residual products.

    In animals

         Methomyl-14C was administered orally to rats (Harvey et al.,
    1973; Baron, 1971). Essentially all the radio-labelled material was
    rapidly eliminated from the body within 24 hours in the ratio of 1
    part 14C-carbon dioxide, 2 parts 14C-acetonitrile and 1 part urinary
    metabolites. Approximately 10% of the original dose was found in the
    whole body and organs one day after treatment. The chemical identity
    of the radio-labelled material excreted in the urine was not
    determined. However, the absence of methomyl, S-methyl
    N-hydroxythioacetimidate, the S-oxide and S,S-dioxide of methomyl and
    conjugates thereof was demonstrated.

    In plants

         The metabolic fate of methomyl was investigated in tobacco, corn
    and cabbage in the laboratory and greenhouse (Harvey & Reiser, 1973;
    Baron, 1971). Plants treated with 14C-methomyl rapidly degraded the
    compound to carbon dioxide and acetonitrile which volatilized from the
    plant tissues. Analysis of the tissues of treated plants showed that
    the remainder of the 14C activity had been reincorporated into
    natural plant components after total decomposition of the methomyl
    molecule. Radio-labelled lipids, Krebs cycle acids (glycolic,
    tartaric), sugars, suspected amino acids and a multiplicity of 14C
    products were identified or detected. The absence of the oxime
    (S-methyl N-hydroxythioacetimidate), the S-oxide and S,S-dioxide of
    methomyl was demonstrated. The only residue found was methomyl itself.
    The half-life of methomyl was of the order of 3-7 days. Repetitive
    season-long treatment of cabbage and corn under field conditions
    confirmed the results obtained with single treatments on young plants
    in the laboratory.

    In soil

         Laboratory studies showed that methomyl was degraded rapidly by
    microbial action in soil with carbon dioxide as the principal product
    (Harvey & Pease, 1973). In soils treated with methomyl under field
    conditions only trace residues of methomyl, its oxime and a polar
    fraction remained after one month, and none was detected after one
    year. Fractionation of the unextractable radioactivity remaining in
    soil five months after treatment with 14C-methomyl showed that the
    water-soluble residual radioactivity was distributed among the normal

    soil organic fractions. This would be expected from reincorporation of
    the 14CO2 or other small fragments formed from the complete
    breakdown of 14C-methomyl. A run-off study with unlabelled methomyl
    under farm use conditions showed that methomyl did not move laterally
    into untreated areas with run-off water.

    In storage and processing

         Some data are available on the effect of cooking and field
    trimming on residue levels of methomyl in some commodities (du Pont de
    Nemours, 1975). Table 8 shows the data on the effect of cooking.
    Residue reduction of about 70-90% was achieved for tomatoes, peas and
    cabbage. Reductions of about 50-90% in methomyl residues resulted from
    trimming celery (Table 9).

         A study was carried out to follow the distribution of methomyl in
    wheat spiked at 0.05, 0.10 and 0.20 mg/kg levels and processed through
    laboratory simulated milling. The data from this study (Table 10) show
    that approximately 20-35% of the methomyl is recovered with the major
    portion in the flour fraction.

    Residues in food in commerce or at consumption

         Data were not available to the Meeting to indicate the level and
    incidence of methomyl residues in food moving in commerce or in food
    at the time of consumption.

    METHODS OF RESIDUE ANALYSIS

         Residues of methomyl can be determined by gas-chromatographic
    methods. Pease & Kirkland (1968) described a method for determining
    residues in animal and plant tissues and soil. Samples were extracted
    with ethyl acetate followed by solvent-partitioning clean-up steps.
    Methomyl was then hydrolysed to the corresponding oxime,
    methyl-N-hydroxythioacetimidate, which was determined by
    programmed-temperature gas chromatography with microcoulometric sulfur
    detection. The limit of determination of the method was 0.02 mg/kg
    based on a 25 g sample, with an average recovery of 93% for all
    tissues investigated. Lower recoveries, averaging 63%, were obtained
    with soils. Pease (1969) modified the method by using the flame
    photometric detector in the sulfur mode, allowing the injection volume
    to be reduced from 50 l to 5 l with the same limit of determination.
    Certain crops (e.g., sweet corn, cabbages) contain troublesome
    interferences and others such as cottonseed and tobacco cause emulsion
    difficulties during the procedure.

         Fung (1975) reported an adaptation of the Pease & Kirkland (1968)
    method for determining methomyl residues in tobacco. The sensitivity
    of the method was 0.01 mg/kg based on a 50 g sample, with an average
    recovery for green and cured tobacco of 87%.

    TABLE 8.  Effect of cooking on residues of methomyl

                                                                             

                                           Residue level
                    Original residue       after cooking        Reduction
    Sample          level (mg/kg)             (mg/kg)              %
                                                                             

    Tomatoes             0.70                 0.18*                74

    Peas                 1.1                  0.09                 92

    Cabbage              16                   1.1                  93

    Water                2.0                  0.56                 72

    Water                10                   3.7                  63
                                                                             

    * Cooking water contained 0.04 mg/kg methomyl.


    TABLE 9.  Effect of trimming on residues of methomyl in celery

                                                                             

                            Pre-harvest
    No. of         Rate     interval       Untrimmed    Trimmed    Reduction
    applications   kg/ha     (days)          mg/kg      mg/kg         %
                                                                             

          3         0.45       3             2.3        0.27          88

          3         0.45       7             1.4        0.25          82

          3         1.8        3             7.4        0.64          91

          3         1.8        7             4.3        0.53          88

          1         0.45       3             2.7        0.8           70

          1         0.9        3             3.4        0.8           77

          1         0.45       2             1.1        0.09          92

          1         0.9        2             3.2        0.25          93

          6         0.9        3             6.9        3.9           44

          6         0.9        5             3.7        1.5           60

          6         0.9        7             1.8        1.0           45
                                                                             

    TABLE 10. Effect of milling wheat on methomyl residues1

                                                                             

                                   Methomyl found, g          Recovered (%)

    Methomyl added, g             Bran         Flour         Bran     Flour
                                                                             

           5.0                     N.D.         1.7           0        34

           10                      0.42         2.6           4        26

           20                      0.65         3.7           3        19
                                                                             

    1  Whole wheat grain was "spiked" and then carried through the milling
       process.


         Mendoza et al. (1974) described a method for determining methomyl
    using 1-fluoro-2,4-dinitrobenzene. Methomyl is hydrolysed to
    methylamine and after reaction with 1-fluoro-2,4-dinitrobenzene, the
    reaction product 2,4-dinitrophenylmethylamine is analysed by GLC with
    electron capture detection. Recoveries of methomyl added to rapeseed
    oil at 0.01-1 mg/kg averaged 97%. This method lacks specificity since
    under the conditions used other methyl carbamate insecticides would
    interfere.

         Williams (1972) reported the direct gas-chromatographic
    determination of methomyl with microcoulometric nitrogen detection but
    did not apply it to samples. Reeves & Woodham (1974) described a
    method for the analysis of methomyl in soil, sediment, water and
    tobacco. Methomyl is extracted from soil, sediment and water with
    dichloromethane and from tobacco with a mixture of dichloromethane and
    benzene. Soil, sediment and water extracts are purified by elution
    through a chromatographic column of activated Florisil, while tobacco
    extracts are purified by a coagulation procedure. Determination is by
    GLC with a sulfur flame photometric detector. The limit of
    determination of the method is 0.05 mg/kg. Average recoveries of 75,
    19, 80 and 78% were obtained for water, soil, sediment and tobacco,
    respectively.

         Methomyl can also be determined by a thin-layer
    chromatographic-enzyme inhibition technique (Mendoza et al., 1974).
    Rape seeds, oils and meals are extracted with ethyl acetate and
    cleaned up by liquid-liquid partitioning. Quantitative recoveries are
    obtained and the limits of detection are 0.01 mg/kg in rape oils and
    meals and 0.03 mg/kg in seeds. McLeod et al. (1975) utilized the same
    detection procedure to analyse fortified food samples. Estimated
    recoveries from milk, eggs, beef, honey, butter, pork, peas and
    cabbage were variable: 70-90% for samples fortified at 0.5 mg/kg and
    40-90% for 0.05 mg/kg.

         None of the methods discussed can be considered satisfactory for
    regulatory purposes. The method of Pease & Kirkland (1968) requires
    resolution of emulsion and interference problems. The method of Reeves
    & Woodham (1974) has been tested on only soil, sediment, water and
    tobacco and requires further validation. The thin-layer
    chromatographic-enzyme inhibition method (Mendoza et al., 1974) is
    semi-quantitative and the dinitrofluorobenzene method (Mendoza et al.,
    1974) is non-specific.

    NATIONAL TOLERANCES REPORTED TO THE MEETING

         Some examples of national tolerances were reported to the Meeting
    and are listed in Table 11.


    TABLE 11.  Examples of National tolerances for methomyl reported to
               the Meeting

                                                                             

                                                                   Tolerance
    Country       Commodity                                        (mg/kg)
                                                                             

    Australia     Soybeans, grapes, rapeseed, citrus fruit,
                  cherries                                            2

                  Leafy vegetables, tomatoes, potatoes, peaches,
                  nectarines, apples, maize, peppers, beans,
                  eggplant                                            1

    Canada        Cabbages                                            5.0

                  Lettuce                                             2.0

                  Citrus fruits                                       1.0

    Netherlands   Peppers, tomatoes                                   0.05

    New Zealand   General                                             0.2

    South Africa  Cabbages, cauliflowers, citrus, green beans,
                  potatoes, peaches, sorghum, maize, tomatoes,
                  tobacco                                             0.2

    United        Alfalfa, bean forage, corn fodder and forage,
    States        pea vines, soybean forage 10
    of America    Spinach                                             6

                  Cabbage, endive (escarole), grapes, lettuce,
                  nectarines, peaches, peas 5
                  Broccoli, celery                                    3

    TABLE 11.  (Cont'd.)

                                                                             

                                                                   Tolerance
    Country       Commodity                                        (mg/kg)
                                                                             

                  Beans (succulent), Brussels sprouts,
                  cauliflower, grapefruit, lemons, oranges,
                  tangerines, mint hay                             2

                  Apples, sorghum forage                           1

                  Cucurbits, fruiting vegetables, leafy
                  vegetables (except broccoli, Brussels sprouts,
                  cabbage, cauliflower, celery, endive
                  (escarole), lettuce and spinach), root crop
                  vegetables, sorghum grain, soybeans              0.2*

                  Beans (dry), corn grain (including popcorn),
                  fresh corn including sweet corn (kernels plus
                  cob with husk removed), cottonseed, peanuts,
                  peanut hulls                                     0.1*
                                                                             

    *  Negligible residues.


    APPRAISAL

         Methomyl is a broad spectrum insecticide that is toxic to insects
    both by direct contact and ingestion. It is used on a considerable
    scale in many countries on a relatively wide range of crops. Methomyl
    is effective against many pests such as beetles, aphids, thrips, leaf
    hoppers and particularly caterpillars, loopers, beet armyworms and
    corn earworms which damage many vegetables, field crops, certain fruit
    crops and commercial plantings of ornamentals.

         Methomyl is marketed in the form of water-soluble powder, water
    miscible solution and wettable powder.

         The rates of application vary depending on part and crop. Normal
    application rates are 0.25-1 kg/ha.

         Extensive residue data were available from the United States of
    America with limited data from Canada, Denmark, Germany, the
    Netherlands, New Zealand, South Africa and the Far East. Methomyl was
    the only residue found. Limited data are available on the fate of
    methomyl residues in storage and processing. No data were available to
    indicate the level and incidence of methomyl residues in food moving
    in commerce or in food at the time of consumption.

         Information is available on the fate of methomyl residues in
    plants, in rats and in soil. In plants the half-life of methomyl is of
    the order of 3-7 days. Methomyl itself is the only residue detected.
    The absence of the oxime (S-methyl N-hydroxythioacetimidate), the
    S-oxide and the S,S-dioxide of methomyl has been demonstrated. The
    molecule is degraded to carbon dioxide and acetonitrile as the major
    residual products which volatilize from the plant tissues.

         In rats methomyl is eliminated from the animal body within 24
    hours in the ratio of 1 part carbon dioxide, 2 parts acetonitrile and
    1 part urinary metabolites. Methomyl, S-methyl
    N-hydroxythioacetimidate, the S-oxide and S,S-dioxide of methomyl and
    conjugates thereof are not present in the urine. Methomyl degrades
    rapidly in soil with carbon dioxide as the principal end product.

         Available residue methods do not appear to be suitable for
    regulatory purposes.

         National tolerances have been established in a number of
    countries.

    RECOMMENDATIONS

         The following guideline levels are recommended.

                                                                             

                                                               Pre-harvest
                                                                intervals
                                              Guideline          on which
                                              level,         recommendations
    Commodity                                 mg/kg          are based (days)
                                                                             

    Cabbage                                     5                  1
    Spinach                                     5                  7
    Lettuce                                     5                  10
    Celery                                      3                  10
    Citrus (oranges, lemons,
      grapefruit, tangelos)                     2                  1
    Apples                                      2                  7
    Snap beans, cauliflower,
      tomatoes, peppers                         1                  3
    Nectarines, grapes                          1                  7
    Hops (dried), tobacco (flue-cured)                             14
    Cucumbers, eggplant                         0.5                3
    Green onions                                0.5                10
    Summer squash, cantaloupes,
      melons, watermelons                       0.2                3
    Asparagus                                   0.2                5
    Green peas                                  0.2                7
    Dry onions, barley, sorghum                 0.2                14
    Pineapples                                  0.2                30

                                                                             

                                                               Pre-harvest
                                                                intervals
                                              Guideline          on which
                                              level,         recommendations
    Commodity                                 mg/kg          are based (days)
                                                                             


    Sweet corn                                  0.1                1
    Potatoes, dry beans                         0.1                3
    Sugar beets                                 0.1                7
    Cottonseed, soy beans, wheat, oats          0.1                14
    Peanuts                                     0.1                21
    Milk, meat                                  0.02*
    Animal feedstuffs: alfalfa, pea
      forage                                    10                 7
      Sorghum and soy bean forage,
      wheat, oat and barley straw               10                 14
      Peanut forage                             5                  21
      Mint hay                                  2                  14
      Peanut hulls                              0.1                21
                                                                             

    * At or about the limit of determination.


    FURTHER WORK OR INFORMATION

    REQUIRED

    1.   Full toxicological data (before an acceptable daily intake can be
         recommended).

    2.   Modification or refinement of available methods of residue
         analysis to make them suitable for regulatory purposes.

    DESIRABLE

    1.   Further data on the disappearance of residues during storage and
         processing.

    2.   Further residue data from countries other than the United States
         of America.

    REFERENCES

    Baron, R. L. (1971) Toxicological considerations of metabolism of
    carbamate insecticides: Methomyl and carbaryl. Pesticide Terminal
    Residues, Tahori, A. S., ed., Butterworths, London, pp. 185-197

    Cochrane, W. P. (1975) Canada Department of Agriculture, Ottawa
    (unpublished report)

    Du Pont de Nemours (1975) Information on methomyl insecticide. E. I.
    Dupont de Nemours & Company (Inc.), Wilmington, Delaware, U.S.A.
    (unpublished)

    Fung, K. K. H. (1975) Determination and identification of S-methyl
    N-((methyl-carbamoyl) oxy) thioacetimidate (methomyl) residues in
    tobacco. J. Agr. Food Chem., 23:695-698

    Greenhalgh, R. (1975) Canada Department of Agriculture, Ottawa
    (unpublished report)

    Harvey, J. jr, Jelinek, A. G. & Sherman, H. (1973) Metabolism of
    methomyl in the rat. J. Agr. Food Chem., 21:769-775

    Harvey, J. jr & Pease, H. L. (1973) Decomposition of Methomyl in soil.
    J. Agr. Food Chem., 21:784-786

    Harvey, J. jr & Reiser, R. W. (1973) Metabolism of methomyl in
    tobacco, corn and cabbage. J. Agr. Food Chem., 21:775-783

    Kiigemagi, U., Wellman, D., Cooley, E. J. & Terriere, L. C. (1973)
    Residues of the insecticides phorate and methomyl in mint hay and oil.
    Pestic. Sci., 4:89-99

    Krueger, H. R., Lindquist, R. K., Mason, J. F. & Spadafora, R. R.
    (1973) Application of methomyl to greenhouse tomatoes: Greenhouse
    whitefly control and residues in foliage and fruits. J. Econ.
    Entomol., 66:1223-1224

    McLeod, H. A., Mendoza, C. E. & McCully, K. A. (1975) Analysis of
    foods for methomyl using thin-layer chromatography after low
    temperature clean-up. Pestic. Sci., 6:11-16

    Mendoza, C. E., Mcleod, H. A., Shields, J. B. & Phillips, W. E. J.
    (1974) Determination of methomyl by using 1-fluoro -2,
    4-dinitrobenzene reaction and gas liquid chromatography. J. Agr. Food
    Chem., 22:255-258

    Pease, H. L. (1969) Modification of the published gas chromatographic
    method for determination of methomyl residues: Use of a flame
    photometric detector. E. I. DuPont de Nemours & Company (Inc.),
    Wilmington, Delaware, U.S.A. (unpublished)

    Pease, H. L. & Kirkland, J. J. (1968) Determination of methomyl
    residues using microcoulometric gas chromatography. J. Agr. Food
    Chem., 16:554-557

    Reeves, R. G. & Woodham, D. W. (1974) Gas chromatographic analysis of
    methomyl residues in soil, sediment, water and tobacco utilizing the
    flame photometric detector. J. Agr. Food Chem., 22:76-78

    Tappan, W. B., Wheeler, W. B. & Lundy, H. W. (1973) Methomyl residues
    in cigar-wrapper and flue-cured tobaccos in Florida. J. Econ.
    Entomol., 66:197-198

    Williams, I. H. (1972) Direct gas chromatographic determination of
    methomyl (LannateR) with microcoulometric nitrogen detection.
    Pestic. Sci., 3:179-181
    


    See Also:
       Toxicological Abbreviations
       Methomyl (EHC 178, 1996)
       Methomyl (HSG 97, 1995)
       Methomyl (ICSC)
       Methomyl (PDS)
       Methomyl (Pesticide residues in food: 1976 evaluations)
       Methomyl (Pesticide residues in food: 1977 evaluations)
       Methomyl (Pesticide residues in food: 1978 evaluations)
       Methomyl (Pesticide residues in food: 1986 evaluations Part II Toxicology)
       Methomyl (Pesticide residues in food: 1989 evaluations Part II Toxicology)
       Methomyl (JMPR Evaluations 2001 Part II Toxicological)