STUDY ON TOXICITY EFFECT OF BISPYRIBAC-SODIUM HERBICIDE ON EARTHWORMS BY FILTER PAPER AND SOIL MIXING METHOD

Two techniques were used to assess the toxicity of the herbicide bispyribac-sodium on earthworms (Aporrectodea caliginosa) by filter paper contact test at 24, 48 and 72 h and soil mixing test at 5 and 10 day. The results obtained in filter paper contact test showed that the concentrations of 1 g a.i mL -1 for herbicide caused 0% mortality at 24 h and 0.01 g a.i mL -1 caused 0% mortality at 48 h. BS showed the highest intrinsic toxicity to the worms with an LC50 value of 0.062 g a.i mL -1 at 72-h compared to LC50 at 48 h was 38.9 g a.i mL -1 and LC50 at 24 h were 518.32 g a.i mL -1 . The toxicity of BS on earthworms by soil mixing technique expressed as LC50 was increased when the exposure time was increased. The LC50 was reduced from 152.92 to 18.59 in clay soil, from 311.60 to 29.63 in clay soil: sandy clay loam soil (1:1) and from 448.23 to 33.67 in sandy soil at 5 and 10 days after treatment, respectively. The toxicity of tested pesticide was greater in clay soil at both time intervals than clay soil: sandy clay loam soil (1:1) and sandy clay loam soil.