PHYSICAL CHEMISTRY Bispyribac Sodium

Composition Tech. is >93%. Mol. wt. 452.4 M.f. C 19 H 17 N 4 NaO 8 ; C 19 H 18 N 4 O 8 for the acid Form White powder. M.p. 223-224 °C V.p. 5.05 ' 10 -6 mPa (25 oC) K OW logP = -1.03 (23 °C) Henry 3.12 ' 10 -11 Pa m 3 mol -1 (calc.) S.g./density Bulk density 0.0737 (20 °C, CIPAC MT 3) Solubility In water 73.3 g/l (25 oC). In methanol 26.3, acetone 0.043 g/l (25 °C). Stability Stable in water; DT 50 >1 y (pH 7 & 9), 448 h (pH 4). Stable to light. Not decomposed after 14 d at 55 °C. pKa 3.05

APPLICATIONS Bispyribac Sodium

Biochemistry Branched chain amino acid synthesis (ALS or AHAS) inhibitor. Mode of action Selective, systemic post-emergence herbicide, absorbed by foliage and roots. Uses Control of grasses, sedges and broad-leaved weeds, especially Echinochloa spp., in direct-seeded rice, at rates of 15-45 g/ha. Also used to stunt growth of weeds in non-crop situations. Formulation types SC; water-soluble liquid.

ANALYSIS Bispyribac Sodium

By hplc. Details available from Kumiai.

MAMMALIAN TOXICOLOGY Bispyribac Sodium

Oral Acute oral LD 50 for male rats 4111, female rats 2635, male and female mice 3524 mg/kg. Skin and eye Acute percutaneous LD 50 for rats >2000 mg/kg. Non-irritating to skin; slightly irritating to eyes (rabbits). Inhalation LC 50 (4 h) for rats >4.48 mg/l. NOEL (2 y) for male rats 20 mg/kg diet (1.1 mg/kg b.w. daily), female rats 20 mg/kg diet (1.4 mg/kg b.w. daily), male mice 14.1 mg/kg daily, female mice 1.7 mg/kg b.w. daily. ADI 0.011 mg/kg. Other Non-mutagenic in the Ames test, and non-teratogenic to rats and rabbits. Toxicity class WHO (a.i.) III (Table 5)

ECOTOXICOLOGY Bispyribac Sodium

Birds Acute oral LD 50 for bobwhite quail >2250 mg/kg. Dietary LC 50 (5 d) for bobwhite quail and mallard ducks >5620 mg/kg diet. Fish Acute LC 50 (96 h) for rainbow trout and bluegill sunfish >100 ppm. Daphnia LC 50 (48 h) >100 ppm. Algae EC 50 (120 h) for Selenastrum capricornutum 3.4 mg/l, NOEC 0.625 mg/l. Bees LD 50 (oral) >200 m g/bee; LC 50 (contact) >7000 mg/l spray. Worms NOEL (14 d) for Eisenia foetida >1000 mg/kg soil.

ENVIRONMENTAL FATE Bispyribac Sodium

Animals >95% of dose applied to rats was excreted in urine and faeces within 7 d. Plants Following application to foliage and soil at 5-leaf stage of rice plants, c. 10% of carbon label was distributed between straw and roots at harvest. Soil/Environment In soil, DT 50 <10 d (flooded and upland conditions).