METALAXYL

Common name: Metalaxyl

Chemical name: methyl N -(2,6-dimethylphenyl)- N -(methoxyacetyl)-= DL -alaninate

Structural formula:

Chemical class: Benzenoid fungicide

CAS No.: 57837-19-1

Properties: Technical product is white crystalline powder. M.p. 63.5-72.3 ℃ . B.p. 295.9 ℃ (101 kPa). V.p. 0.75 mPa (25 ℃ ). Soluble in water 8.4g/L (22 ℃ ). In ethanol 400, acetone 450, toluene 340, n-hexane 11, n-octanol 68 (all in g/L, 25 ℃ ). Stable up to 300 ℃ . Stable in neutral and acidic media at room temperature.

Toxicity: Acute oral LD 50 for rats 633, mice 788, rabbits 697 mg/kg. Acute percutaneous LD 50 for rats ﹥ 3100 mg/kg; slight irritant to eyes, not irritant to skin of rabbits. No skin sensitization (guinea pigs). Inhalational LC 50 (4 h) for rats ﹥ 3600 mg/m 3 .

Ecotoxicology: Birds, LD 50 for mallard ducks (8 d) 1466 mg/kg. LC 50 (8 d) for bobwhite quail and mallard ducks ﹥ 10000 mg/kg. Fish, LC 50 (96 h) for rainbow trout, carp, and bluegill sunfish ﹥ 100mg/L. Bees, not toxic to bees; LD 50 (48 h) (contact) ﹥ 200, (oral) 269.3 µ g/bee. Worms, LC 50 (14 d) for Eisenia foetida ﹥ 1000 mg/kg soil. Daphnia, LC 50 (48 h) ﹥ 28 mg/L.

Environmental fate: Animals, in mammals, following oral administration, metalaxyl is rapidly absorbed and also rapidly and almost completely eliminated with urine and faeces. Metabolism proceeds via hydrolysis of the ester bond, oxidation of the 2-(6)-methyl group and of th ephenyl ring and N-dealkylation. Residues in tissues were generally low and there was no evidence for accumulation or retention of metalaxyl or its metabolites. Plants, metalaxyl is metabolized by more than 4 types of phase I reaction to form eight metabolites; at phase II, most of the metabolites are sugar conjugated. The types of reaction in phase I are: oxidation of the phenyl ring, oxidation of the methyl group, cleavage of the methyl ester and N-dealkylation. Soil/Environment, in soil, DT 50 19 d, DT 90 90d. Koc 30-300 ml/g. DT 50 in water 22-48 d. Photolytically stable in water.

Treatment: Get medical aid. Eyes, flush immediately with plenty of water. Skin, wash with soap and water. Remove contaminated clothing and shoes. Inhalation, remove to fresh air. Ingestion, drink 1-2 glasses of water.

Mode of action: Systemic fungicide with protective and curative action, absorbed through the leaves, stems, and roots.

Usage: Used to control diseases caused by air- and soil- borne Peronosporales on a wide range of temperate, subtropical and tropical crops. Foliar sprays with mixtures of metalaxyl and protectant fungicides are recommended to control air-borne diseases caused by Pseudoperonospora humuli on hops, Phytophthora infestans on potatoes, Peronospora tabacina on tobacco, and Plasmopara viticola on vines. Soil applications of metalaxyl alone are used to control soil-borne pathogens causing root and lower stem rots on avocado and citrus; also recommended for primary systemic infections of P. humuli on hops and in tobacco seed beds. Seed treatments control systemic Peronosporaceae on maize, peas, sorghum and sunflowers, as well as damping-off ( Pythium spp.) of various crops.