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Metribuzin |
| Chemical name： |
4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one |
| Molecular weight： |
214.3
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| Molecular formular： |
C8H14N4OS |
Mode of action： |
Selective systemic herbicide, absorbed predominantly by the roots, but also by the leaves, with translocation acropetally in the xylem. |
Uses： |
Pre- and post-emergence control of many grasses and broad-leaved weeds in soya beans, potatoes, tomatoes, sugar cane, alfalfa, asparagus, maize and cereals, at 0.07-1.45 kg/ha. Phytotoxicity Phytotoxic to many crops, including crucifers, cucurbits, lettuce, onions, sugar beet, sunflowers, flax, strawberries, sweet potatoes, and tobacco. |
Physical chemistry： |
Form White crystals, with a weak characteristic odour. M.p. 126 °C B.p. 132 °C/2 Pa. V.p. 0.058 mPa (20 °C) Kow logP = 1.6 (pH 5.6, 20 °C) Henry 1 × 10-5 Pa m3 mol-1(20 °C, calc.) S.g./density 1.26 (20 °C)
Solubility In water 1.05 g/l (20 °C). In dimethyl sulfoxide, acetone, ethyl acetate, dichloromethane, acetonitrile, isopropanol, polyethyleneglycol >250, benzene 220, xylene 60, n-octanol 54 (all in g/l, 20 °C). Stability Relatively stable to u.v. irradiation. At 20 °C, stable to dilute acids and alkalis; DT50 (37 °C) 6.7 h (pH 1.2); DT50 (70 °C) 569 h (pH 4), 47 d (pH 7), 191 h (pH 9). Photodecomposition in water is very rapid (DT50<1 d). On soil surfaces under natural light conditions, DT50 14-25 d. |
Mmmalian toxicology： |
Oral Acute oral LD50 for male rats 510, female rats 322, mice c. 700, guinea pigs c. 250, cats >500 mg/kg. Skin and eye Acute percutaneous LD50 for rats >20 000 mg/kg. Not irritating to skin and eyes (rabbits). Inhalation LC50 (4 h) for rats >0.65 mg/l air (dust). NOEL (2 y) for rats and dogs 100, mice c. 800 mg/kg diet. ADI 0.013 mg/kg b.w. Toxicity Class WHO (a.i.) II; EPA (formulation) III EC classification Xn; R22| N; R50, R53 (also draft concn. dep. assignments) |
Ecotoxicology： |
Birds Acute oral LD50 for bobwhite quail 164, mallard ducks 460-680 mg/kg. Fish LC50 (96 h) for rainbow trout 74.6, golden orfe 141.6, sheepshead minnows 85 mg/l. Daphnia LC50 (48 h) 49.6 mg/l. Algae ErC50 for Scenedesmus subspicatus 0.021 mg/l. Bees Not toxic to bees; LD50 35 μg/bee. Worms LC50 for Eisenia foetida 331.8 mg/kg dry soil. |
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