Toxicity of selective insecticides to Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae), a parasitoid of the American serpentine leafminer Liriomyza trifolii (Burgess) (Diptera: Agrizomydae)

The susceptibilities of Neochrysocharis formosa, a larval parasitoid of the American serpentine leafminer Liriomyza trifolii, to three insecticides (imidacloprid, pymetrozine and lufenuron) were investigated in the laboratory. Individual parasitoids were placed in the grass vials whose internal surface was coated with the insecticides. For 24 h exposure, the LC₅₀ values were 0.033 μg/0.5 ml for imidacloprid, 75.57 μg/0.5 ml for pymetrozine and 0.417 μℓ/0.5ml for lufenuron. For imidacloprid and lufenuron, these values were 775.5 and 14.9 times lower than the recommended concentrations, respectively. Even in the concentrations lower than the LC₅₀, parasitoid survival rapidly decreased with time, and the longevity of parasitoid females was also reduced. These results suggested that all of imidacloprid, pymetrozine and lufenuron were harmful to N. formosa.