Physiological selectivity of insecticides to wasps (Hymenoptera: Vespidae) preying on the diamondback moth.

摘要

In the present study, we evaluate the toxicity of seven insecticides to the predatory wasps Brachygastra lecheguana, Protonectarina sylveirae, Polybia scutellaris and Polybia fastidiosuscula (Hymenoptera: Vespidae), relative to Plutella xylostella (Lepidoptera: Plutellidae). Adults of the predatory wasps and larvae of P. xylostella were exposed to nine concentrations of carbaryl, cartap, deltamethrin, methamidophos, methyl parathion, permethrin and trichlorfon. Selectivity, toxicity, and tolerance ratios were calculated from LC₅₀ values to determine insecticide toxicity to predatory wasps and P. xylostella as well as insecticide tolerance of the predatory wasps. The predatory wasps showed steeper slopes in concentration-mortality regression lines for insecticides than the P. xylostella. Overall, the insecticides showed no selectivity in favor of predatory wasps, thus the LC₅₀ were higher for P. xylostella than for predatory wasps. Cartap showed selectivity to the predatory wasps B. lecheguana, and P. sylveirae and trichlorfon was selective to P. sylveirae. The mortality of P. scutellaris estimated by all insecticides tested was higher than 95%. In addition, the mortalities of B. lecheguana, P. sylveirae, and P. fastidiosuscula by all insecticides tested were higher than 80%, except for cartap, which caused 41, 42 and 71% wasp mortality, respectively. P. fastidiosuscula was the most susceptible wasp to the majority of the insecticides as indicated by lower LC₅₀ values for the insect relative to the other wasps. Deltamethrin and permethrin were the most potent insecticides against B. lecheguana and P. sylveirae, as were deltamethrin and methyl parathion against P. scutellaris, and carbaryl, deltamethrin and methyl parathion against P. fastidiosuscula.