Abstract:
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 µg a.i mL-1
for herbicide caused 0% mortality at 24 h and 0.01 µg 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 µg a.i mL-1
at 72-h compared to LC50 at 48 h was 38.9 µg a.i mL-1
and LC50 at 24
h were 518.32 µg 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. |
