Insecticide toxic effects on Trichogramma ostriniae (Hymenoptera: Trichogrammatidae)

Abstract

Background: The parasitoid Trichogramma ostriniae (Pang and Chen) is a major natural enemy of many lepidopterans, but only a few studies have been conducted on the compatibility of biological and chemical controls. In this study, the selectivity of 30 insecticides to T. ostriniae adults was evaluated.

Results: Among the seven classes of chemicals tested, organophosphates and carbamates had the highest intrinsic toxicity to the wasp, with LC(50) values ranging from 0.032 (0.029-0.038) to 2.38 (1.91-3.15) mg AI L(-1). They are followed by phenylpyrazoles, avermectins, neonicotinoids and pyrethroids, which induce variable toxicity responses, with LC(50) values ranging from 0.14 (0.11-0.21) to 56.67 (48.94-67.24) mg AI L(-1), from 2.57 (1.85-4.28) to 4.48 (3.34-6.83) mg AI L(-1), from 2.48 (1.80-4.03) to 503.6 (457.6-557.5) mg AI L(-1) and from 5.44 (3.95-8.84) to 104.2 (92.48-119.7) mg AI L(-1) respectively. The insect growth regulators (IGRs) exhibited least toxicity to the parasitoid.

Conclusion: Risk quotient analysis classifies neonicotinoids, avermectins, pyrethroids, IGRs and phenylpyrazoles (with the exception of butane-fipronil and fipronil) as safe agents to the parasitoid, but categorises organophosphates and carbamates as slightly to moderately toxic or dangerous to T. ostriniae.