METHOMYL

Common name: Methomyl

Chemical name: Ethanimidothioic acid, N-{{(methylamino)carbonyl}oxy}-, methyl ester

Structural formula:

Chemical class: Carbamate insecticide

CAS No.: 16752-77-5

Properties: Technical product is white powder. M.p. 78-79 ℃ , V.p. 0.72 mPa (25 ℃ ). Soluble in water 57.9g/L (25 ℃ ). In methanol 1000, acetone 730, ethanol 420, isopropanol 220, toluene 30 (all in g/kg, 25 ℃ ). Sparingly soluble in hydrocarbons. At room temperature, aqueous solutions undergo slow decomposition. The rate of decomposition increases at higher temperatures, in the presence of sunlight, on exposure to air, and in alkaline media.

Toxicity: Acute oral LD 50 for male rats 17 mg a.i./kg, for female rats 24 mg/kg. Acute percutaneous LD 50 for male rabbits ﹥ 5000mg a.i./kg; irritant to eyes of rabbits but not to skin of guinea pigs. Inhalational LC 50 (4 h) for rats 0.3 mg/L air (aerosol).

Ecotoxicology: Birds, acute oral LD 50 for mallard ducks 15.9, pheasants 15.4 mg/kg. Eight-day dietary LC 50 for Pekin ducks 1890, bobwhite quail 3680 mg/kg diet. Fish, LC 50 (96 h) for rainbow trout 3.4, bluegill sunfish 0.9 mg/L. Bees, toxic to bees, contact LD 50 0.1 µ g/bee, but not hazardous when the spray has dried. Daphnia, LC 50 (48 h) 28.7 µ g/L.

Environmental fate: Animals, in rats, methomyl was rapidly converted to methomyl methylol, oxime, sulfoxide and sulfoxide oxime; these unstable intermediates were converted to acetonitrile and CO 2 , which were eliminated primarily via respiration and in the urine. Metabolism of carbamate insecticides is reviewed. Plants, DT 50 following leaf application c. 3-5 d. Rapidly degraded to CO 2 and acetonitrile, with incorporation into natural plant components. Soil/Environment, rapidly degraded in soil. DT 50 in groundwater samples ﹤ 0.2 d. Koc 72.  

Treatment: Antidote: Atropine. Consult physician in all cases of suspected poisoning. Do NOT use morphine or 2-PAM. Except for exposure to methomyl and organophosphorous insecticides, 2-PAM may be used to supplement atropine sulfate treatment.

Mode of action: Systemic insecticide and acaricide with contact and stomach action.

Usage: Control of a wide range of insects (particularly Lepidoptera, Hemiptera, Hemiptera, Homoptera, Diptera and Coleoptera) and spider mites in fruit, vines, olives, hops, vegetables, ornamentals, field crops, cucurbits, flax, cotton, tobacco, soya beans, etc. Also used for control of flies in animal and poultry houses and dairies.