Residual Toxicity of Avermectin b1 and Pyridaben to Eight Commercially Produced Beneficial Arthropod Species Used for Control of Greenhouse Pests

Residual toxicities of avermectin b1 and pyridaben for 2- to 28-day exposure periods were assessed in laboratory and greenhouse trials for eight species of beneficial arthropods that are commercially produced for greenhouse pest management. In laboratory trials, Amblyseius degenerans Berlese, Aphidius colemani Viereck, Aphidoletes aphidimyza (Rondani), Dacnusa sibirica Telenga, Encarsia formosa (Gahan), and Orius insidiosus (Say) showed high mortality (>85%) when exposed to ≤6-day residues of both acaricides. Lower toxicities were observed for pyridaben to the predatory mites Amblyseius cucumeris (Oudermans) and Phytoseiulus persimilis Athias-Henroit and for avermectin b1 to A. cucumeris after exposure to ≤6-day residues. In greenhouse trials, pyridaben showed significantly higher residual toxicity to all beneficial species than avermectin b1. Pyridaben had high residual toxicity (40–60% mortality) to E. formosa, A. colemani, A. aphidimyza, A. degenerans, and P. persimilis 6 days after treatment. Residual toxicity of pyridaben to D. sibirica, A. cucumeris, and O. insidiosus decreased to a low level (<15% mortality) after 6 days. Avermectin b1 was slightly toxic or nontoxic to the predaceous mites A. cucumeris, A. degenerans, and P. persimilis. Toxicity of avermectin b1 to E. formosa, A. colemani, D. sibirica, and O. insidiosus rapidly decreased to <25% mortality 6 days after application. Based on the results of the greenhouse trials, avermectin b1 was considered suitable for use with predacious mites and could be combined in integrated pest management (IPM) programs with other beneficial species after residual toxicity is taken into consideration. Pyridaben can also be combined in IPM programs with A. cucumeris, O. insidiosus, and D. sibirica after a 6-day residual period.