PHYSICAL CHEMISTRY Diclofop methyl
diclofop-methyl
Composition Tech. grade is ³93% pure. Mol. wt. 341.2 M.f. C16H14Cl2O4 Form Colourless crystals. M.p. 39-41 ºC V.p. 0.25 mPa (20 ºC); 7.7 mPa (50 ºC) (vapour pressure balance) KOW logP = 4.58 S.g./density 1.30 at 40 ºC Solubility In water 0.8 mg/l (pH 5.7, 20 ºC). In acetone, dichloromethane, dimethyl sulfoxide, ethyl acetate, toluene >500 g/l; in polyethylene glycol 148, methanol 120, isopropanol 51, n-hexane 50 (all in g/l, 20 ºC). Stability Stable to light. In water, DT50 (25 ºC) 363 d (pH 5), 31.7 d (pH 7), 0.52 d (pH 9).
COMMERCIALISATION Diclofop methyl
History Herbicidal activity of diclofop-methyl reported by P. Langelüddeke et al. (Mitt. Biol. Bundesanst. Land.-Forstwirtsch. Berlin-Dahlem, 1975, 165, 169). Introduced by Hoechst AG (now Aventis CropScience). Patents DE 2136828; DE 2223894 Manufacturers Aventis; Hegang Heyou; Jingma; Sundat; Tide
USES Diclofop methyl
Uses For post-emergence control of wild oats, wild millets, and other annual grass weeds in wheat, barley, rye, red fescue, and broad-leaved crops such as soya beans, sugar beet, fodder beet, flax, legumes, oilseed rape, sunflowers, clover, alfalfa, peanuts, brassicas, carrots, celery, beetroot, parsnips, lettuce, spinach, potatoes, cucumbers, peas, beans, tomatoes, fennel, alliums, herbs, etc.
ANALYSIS Diclofop methyl
Product analysis by glc (CIPAC Handbook, 1985, 1C, 2096). Details of glc methods for product and residue analysis are available from Aventis.
MAMMALIAN TOXICOLOGY Diclofop methyl
Oral Acute oral LD50 for rats 481-693 mg/kg (in sesame oil), dogs 1600 mg/kg (highest dose without induction of vomiting). Skin and eye Acute percutaneous LD50 for rats >5000 mg/kg. Inhalation LC50 for rats >1.36 mg/l air. NOEL (2 y) for rats 0.1 mg/kg b.w.; (15 mo) for dogs 0.44 mg/kg b.w. ADI 0.001 mg/kg b.w. (AgrEvo proposed value). Other Non-mutagenic in the Ames test. Toxicity class WHO (a.i.) III; EPA (formulation) III EC hazard Xn; R22, R43| N; R50, R53
ECOTOXICOLOGY Diclofop methyl
Birds Acute oral LD50 for Japanese quail >10 000 mg/kg. Dietary LC50 (5 d) for bobwhite quail >1600, mallard ducks >1100 mg/kg b.w. Fish LC50 (96 h) for rainbow trout 0.23 mg/l. Daphnia LC50 (48 h) 0.23 mg/l. Algae EC50 (72 h) for Scenedesmus subspicatus 1.5 mg/l, (120 h) for Selenastrum capricornutum 0.53 mg/l. Bees Non-toxic to bees under field conditions and application rate of 1.134 kg a.i./ha. Worms LC50 (14 d) for earthworms >1000 mg/kg soil, dry weight.
ENVIRONMENTAL FATE Diclofop methyl
Animals When fed to rats, diclofop-methyl is almost totally absorbed and then rapidly excreted; c. 90% is recovered unchanged in faeces and urine after 2 d, and 99% after 7 d. Accumulation of residues in the body is unlikely; low levels of total residues were found in organs and tissues 7 d after a single dose of 1.8 mg/kg b.w. Metabolites are identical with those in plants. Plants Diclofop-methyl is taken up rapidly and almost completely by plants, with little translocation. It is hydrolysed relatively quickly (DT50 in sugar beet 3 d), first to an isomeric mixture of hydrolysed free acids and their conjugates with glucuronic and sulfuric acid, and then to 4-(2,4-dichlorophenoxy)phenol. Total radioactive residues at the time of harvest in wheat, sugar beet and soya beans are generally low, below or around the determination limits (0.01 to 0.1 mg/kg). The same applies to rotation crops. Soil/Environment In soil, diclofop-methyl is metabolised to diclofop, which then undergoes further degradation to 4-(2,4-dichlorophenoxy)phenol, hydroxylated free acids and CO2. In various soils in field trials: DT50 1-57 d, DT90 30-281 d. Irrigation studies indicate low levels of leaching. From model calculations, a hazard to groundwater or to drinking water supplies can be excluded, even in sandy soil. Soil adsorption Koc 14 000-24 400 mg/kg.
