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    CHLOROTHALONIL        JMPR 1978

    Explanation

         Chlorothalonil was reviewed by the Joint Meeting in 1974 and
    1977 (FAO/WHO, 1975b, 1978b). During the tenth session of the Codex
    Committee on Pesticide Residues, data were promised that would
    allow MRLs for new commodities to be recommended (Alinorm 79/24,
    para 153). The data received are evaluated in this monograph
    addendum.

    RESIDUES IN FOOD AND THEIR EVALUATION

    USE PATTERN

         Data were available on residues in some cereals, in grapes and
    in strawberries. There was insufficient information on the
    registered uses in grapes and strawberries to establish MRLs or the
    basis of good agricultural practice, Although information on
    registered use for cereals was also scarce, it was considered that
    an MRL could be proposed on the basis of an interval of 6 weeks
    between last application and use, Residues data are based on the
    use of a 75% wettable powder, a 720 g/l liquid and a wettable
    powder containing 20% chlorothalonil, 22% zineb and 40% sulphur.

    RESIDUES RESULTING FROM SUPERVISED TRIALS

         The data on residues of chlorothalonil in some types of
    cereals are summarized in Table 1 (de Mey, 1977).

    National MRLs reported to the Meeting

         In addition to the national MRLs reviewed by the 1974 JMPR,
    the following were reported.

             Country        Commodity      MRL (mg/kg)

             Japan          cereals        0.5

             Netherlands    cereals        0.2

             Switzerland    cereals        0.3

    APPRAISAL

         On the basis of the residue data on winter wheat, summer wheat
    and winter barley, it appears that after use of chlorothalonil at
    1 to 3 kg ai/ha and taking into account a period of 6 weeks between
    the last application and harvest, a temporary maximum residue limit
    of 0.2 can be recommended.


    
    TABLE 1. Chlorothalonil in cereals

                                                                                                                                         

                                                         Residues (mg/kg) at interval (days) after application
    Crop           Year   Rate kg ai/ha    Formulation                                                                                   
    (Country)             1/(application
                          unless indicated)              24     28     30      36     42      43      45       47      52      56     61
                                                                                                                                         

    Winter wheat   1975        1.2         wp 20%                                                              0.02

    Winter wheat   1975        1.2         wp 20%                                                              <0.01
    (Belgium)
                                                                                                                                         

    Winter wheat   1974        1.5         wp 75%                                                                              0.16

    Winter wheat   1974        1.5         wp 75%                                                                      0.01

    Winter wheat   1974        1.5         wp 75%                                             <0.01

    Winter wheat   1975        1.5         wp 75%               <0.01          <0.01

    Winter wheat   1975      n.i.1/        liquid               <0.01          <0.01

    Winter wheat   1975       1.62         liquid                      0.068
                                           720 g/l

    Winter wheat   1976       1.08         liquid                                                     0.021
                                           720 g/l

    Winter wheat   1976       1.08         liquid         0.088
    (Germany)                              720 g/l
    
                                                                                                                                         

    TABLE 1. (Cont'd)

                                                                                                                                         

                                                         Residues (mg/kg) at interval (days) after application
    Crop           Year   Rate kg ai/ha    Formulation                                                                                   
    (Country)           1/(application
                        unless indicated)                24     28     30      36     42      43      45       47      52      56     61
                                                                                                                                         

    Winter wheat   1974        1.2         wp 20%                                     0.52
    (ears & grain)

    Winter wheat   1974       +1.2         wp 20%                                     0.46
    (ears & grain)
    (Netherlands)
                                                                                                                                         

    Wheat          1970       1.08         flowable                                                                            0.01

    Wheat          1970       1.08         flowable                                                                            0.0175

    Wheat          1970       1.08         n.i.1/                                                                              0.01

    Wheat          1970       1.08         n.i.1/                                                                              0.01

    Wheat          1976       1.08         n.i.1/                                                                              0.0105

    Wheat          1976       1.08         n.i.1/                                                                              0.0155
    (France)
                                                                                                                                         

    Wheat          1975       2.51         wp 75%                                                                              <0.01

    Wheat          1975       2.51         wp 75%                                                                              <0.01
    (U.K.)
                                                                                                                                         

    TABLE 1. (Cont'd)

                                                                                                                                         
                                                         Residues (mg/kg) at interval (days) after application
    Crop           Year   Rate kg ai/ha    Formulation                                                                                   
    (Country)            1/ (application
                        unless indicated)                21     31     35      39     40      41      47       48      49      61
                                                                                                                                         

    Summer wheat   1974       1.125        wp 20%                                                                              <0.01

    Summer wheat   1975       1.62         liquid
                                           720 g/l                                    0.29

    Summer wheat   1975       1.62         liquid
                                           720 g/l                                            0.03

    Summer wheat   1976       1.08         liquid
                                           720 g/l                     0.04

    Summer wheat   1976       1.08         liquid
                                           720 g/l              0.097

    Summer wheat   1976       1.08         liquid
                                           720 g/l                                                                     0.04

    Summer wheat   1976       1.06         liquid
                                           720 g/l       0.777
    (Germany)
                                                                                                                                         

    Winter barley  1976        1.7         liquid
                                           720 g/l                                                    <0.01

    Winter barley  1976        1.7         liquid
                                           720 g/l                             0.09

    TABLE 1. (Cont'd)

                                                                                                                                         

                                                         Residues (mg/kg) at interval (days) after application
    Crop           Year   Rate kg ai/ha    Formulation                                                                                   
    (Country)            1/(application
                        unless indicated)                21     31     35      39     40      41      47       48      49      61
                                                                                                                                         

    Winter barley  1976        1.7         liquid
                                           720 g/l                                                    <0.01

    Winter barley  1976        1.7         liquid
                                           720 g/l                             0.10

    Winter barley  1976        1.7         liquid
                                           720 g/l                                                             <0.01

    Winter barley  1976        1.7         liquid
                                           720 g/l                             0.07
    (Belgium)
                                                                                                                                         

    Winter barley  1975        1.5         wp 75%                                                                              <0.01
                                                                                                                               100 days

    Winter barley  1975     1.5 + 1.5      wp 75%                                                                              <0.01
    (Tunisia)                                                                                                                  80 days
                                                                                                                                         

    1/ not indicated
    

    RECOMMENDATIONS

         In addition to former recommendations the following temporary MRL
    is proposed:

            Commodity      Temporary MRL       Pre-harvest interval

            Cereals        0.2                 6 weeks

    REFERENCES

    de Mey, W. Residue Analysis of Chlorothalonil in cereals, Vol. I
    (1977)         and II.

    FAO/WHO Pesticide Residues in Food 1974.
    (1975b)

    FAO/WHO Pesticide Residues in Food 1977.
    (1978)
    


    See Also:
       Toxicological Abbreviations