PMEP Home Page Pesticide Fact Sheets and Tutorials Physical-Chemical Parameters Physical/Chemical Parameters:Methamidophos

Methamidophos

      PESTICIDE NAME: Methamidophos
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      Trade name(s): Monitor
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      Manufacturer(s): Chevron Chemical Co.
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                       Ortho Agr. Chem. Div.
                       575 Market Street, P.O. Box 3744
                       San Francisco, CA.  94105
                       Mobay Chemical Corp.
                       Agr. Chem. Div.
                       P.O. 4913
                       Kansas City, MO.  64120
      I.  Basic information
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          A. Molecular structure: C2H8NO2PS
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          B. Chemical name: O,S-Dimethyl phosphoramidothioate
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          C. Derivatives: Methamidophos is a derivative of acephate through
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      S-demethylation
          D. Molecular weight: 141.1 grams/mole
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          E. Solubility in water: very soluble
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          F. Common physical appearance: crystalline
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          G. Oral LD50(rat): 18.90-21 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: cabbage, cauliflower, broccoli, Brussels sprouts
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      II.  Text
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           Methamidophos is a very soluble organophosphate insecticide used
      on a few selected vegetable crops in New York.  The scientific
      literature does not contain significant information on methamidophos.
      III. Soils information
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           A.  Degradation and transformation
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           Acephate degrades through S-demethylation to form
      methamidophos(1).  The literature contains no substantial information
      concerning methamidophos degradation.
           B.  Adsorption and transport
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           Because methamidophos is produced in soil from acephate, it is
      rapidly absorbed by the plant thus indicating little adsorption of
      methamidophos in soil.  The concentration of methamidophos in
      tobacco-cropped soil = 1.6ppm 5d after application decreasing to
      ~0.01ppm at 15d; on uncropped soil, methamidophos concentration =
      0.005ppm at 20d, 0.003ppm at 30d (2).
      IV. References
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      1.Focht, D.D., H. Joseph. 1974.  JEQ. 3(4). 327-8.
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      2.Yamazaki, M. M. Sakai and F. Goto. 1982.  Journal of Pesticide
                                                  ____________________
           Science.  7(2). 175-80.
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