Effect of Temperature on Toxicity and Knockdown Activity of cis-Permethrin, Esfenvalerate, and λ-Cyhalothrin in the Cabbage Looper (Lepidoptera: Noctuidae)

The time required for two symptoms of poisoning, ataxia and prostration (i.e., knockdown), to occur in third-instar cabbage loopers, Trichoplusia ni (Hübner), treated topically with cis-permethrin, esfenvalerate, and λ-cyhalothrin was determined at 15.6, 26.7, and 37.8°C. The toxicity of the pyrethroids also was examined at the three temperatures. ci8-Permethrin and λ-cyhalothrin had negative temperature coefficients of toxicity between 15.6 and 37.8°C, whereas esfenvalerate was equally toxic at both temperatures. The onset of ataxia and prostration in larvae treated with these pyrethroids occurred more rapidly as the temperature increased, thus was positively correlated with temperature. λ-Cyhalothrin was the most toxic pyrethroid; however, cis-permethrin was generally the most effective in producing ataxia and prostration in treated larvae.