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Azinphos methyl

      PESTICIDE NAME: Azinphos methyl
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      Trade name(s): Guthion
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      Manufacturer(s): Mobay Chemical Corporation
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                       Agricultural Chemicals Division
                       P.O. Box 491
                       Kansas City , Mo. 64120
      I.  Basic information
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          A. Molecular structure: C10H12N3O3PS2
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          B. Chemical name: O,O-dimethyl phosphorodithioate S-ester with
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      3-(mercaptomethyl)-1,2,3-benzotriazin-4(3H)-one
          C. Derivatives: N-methyl benzamide sulfide; N-methyl benzamide
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      disulfide; N-methyl benzamide
          D. Molecular weight: 317.1 g/mole
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          E. Solubility in water: 29 mg/l
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          F. Common physical appearance: colorless crystals (pure compound)
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          G. Oral LD50(rat): 16 mg/kg
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          H. Pesticide classification: organophosphate insecticide
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          I. Restricted use list (N.Y.): yes
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           EPA priority pesticide list: no
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           J. Crop use: apple, pear, peach, apricot, plum, prune, cherry,
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      raspberry, grape, blackberry, strawberry, blueberry, beans, celery,
      broccoli, cabbage, cauliflower, Brussels sprouts, cucurbits, peppers,
      potato, eggplant, spinach, tomato
      II. Text
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           Azinphos methyl is a fairly immobile, short-lived organophosphate
      insecticide used on a variety of fruit, vegetable and ornamental crops
      in N.Y. state.  It is rapidly converted to its derivatives which are
      more persistent than the parent compound, not subject to leaching and
      eventually degraded.Degradation follows first-order kinetics.
      III. Soils information
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           A. Degradation and transformation
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           The disappearance of azinphos methyl from soil is estimated to be
      2-4wks(1), less than one year(1,3), and after 30d at 40deg C in sandy
      loam with a half-life in sandy loam of 5d(5).  Derivatives were not
      found in a field soil after 4yrs(3).  A lag time before the chemical's
      disappearance has been seen inboth sterile and non-sterile soils, thus
      the degradation is not strictly biological.  Degradation does follow
      first-order kinetics(6).  Disappearance of azinphos methyl from soil is
      more rapid in the 0-2.5cm layer than at 2.4-7.5cm due to exposure to
      elements, photodecomposition, hydrolysis, and volatilization(4). The
      photodecomposition is especially evident with high soilmoisture and in
      the presence of UV light.  Volatility of azinphos methyl is considered
      to be low.  In the lab a 95% disappearance has been reported after 6d
      for analytical grade azinphos methyl and after 22d for diluted
      emulsifiable concentrate.  In the field, a 50% loss was reported after
      12d for emulsion on the soil surface and at 28d for granular form
      roto-tilled into the top 4-5 in(3).
           The tables below present data concerning azinphos methyl
      degradation.  The reference is given in parentheses at the end of each
      title.
      The half-life of azinphos methyl in sterile and non-sterile soils and
      at varying temperatures(6)
                                    half-life (days)
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                        sterile                 non-sterile
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          deg C      dry       wet           dry         wet
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           6        484        88           484          64
          25        135        29            88          13
          40         36         6            32           5
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      Effect of temperature and moisture content on degradation rate of
      azinphos methyl in soil. k1 is rate constant or proportionality
      constant for reaction(6)
      wet soil, soil temp. = 6deg C   k1 = 8.5 x 10 3
                            40deg C   k1 = 1.3 x 10 1
      soil temp. = 25deg C, dry soil  k1 = 6.1 x 10 3
                            wet soil  k1 = 2.8 x 10 2
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           B. Adsorption and transport
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           The information in the scientific literature is not extensive
      concerning movement of azinphos methyl in soil.  The chemical is
      considered to be fairly immobile (1,4,5) and its adsorption is
      influenced by soil type(1).  Azinphos methyl has been reported to be
      retained in the upper 30cm layer(4,5), and the upper 2in(2) of the soil
      column.
      IV. References (*denotes key reference)
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       1.Kahn, S.U.  Pesticides in the Soil Environment. 1980.  Amsterdam:
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           Elsevier.
       2.Kuhr, R.J., A.C. Davis and J.B. Bourke. 1974.  Bull. Env. Contam.
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           Toxiocol.  11. 224-30.
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      *3.Schulz, K.R., E.P. Lichtenstein, T.T. Liang, and T.W. Fuhremann.
           1970. J.Econ.Ento. 63. 432-8.
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       4.Staiff, D.C., S.W. Comer, J.F. Armstrong, and H.R. Wolfe.  1975.
             Bull.Environ.Contam.Toxicol. 13. 362-8.
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      *5.Yaron, B., H. Bielorai and L. Kliger. 1974.  JEQ. 3. 413-17.
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      *6.Yaron, B., B. Hever and Y. Birk. 1974.  J.Agr.FoodChem. 22. 439-41.
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