| Summary: | Topical bioassays were conducted to evaluate the
toxicity of deltamethrin, cypermethrin, y-HCH and
chlopyrifos against 3 populations of H. theivora
namely the cocoa populations (Serdang. Selangor)
and Sungai Tekam, Pahang) and tea population
(Banting. Selangor). The synergistic effects of
piperonyl butoxide (PBO), maleic acid diethyl ether
(MADE) and s.s.s-tributyl phosphorotrittlioate (DEF)
were also tested using similar technique. Based on
the LDso values, the toxicity ofthe insecticide tested
for the Serdang and Sungai Tekam populations were
chlopyrifos > y-HCH > cypermethrin >
delWnethrin; forthe Banting population was y-HCH
> cypermethrin > chlorpyrifos > deltamethrin. The
most toxic insecticide was chlopyrifos with LD50
value of 3.028 x 10-2mg/l for the Sungai Tekam
population. The synergism of PBO on cypermethrin was higher compared to other insecticides tested.
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