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 exposur e periods were assessed in laboratory and greenhouse trials for eight speci es of beneficial arthropods that are commercially produced for greenhouse p est management. In laboratory trials, Amblyseius degenerans Berlese, Aphidi us colemani Viereck, Aphidoletes aphidimyza (Rondani), Dacnusa sibirica Tel enga, Encarsia formosa (Gahan), and Orius insidiosus (Say) showed high mort ality (>85%) when exposed to less than or equal to 6-day residues of both a caricides. Lower toxicities mere observed for pyridaben to the predatory mi tes Amblyseius cucumeris (Oudermahs) and Phytoseiulus persimilis Athias-Hen roit and for avermectin bl to A. cucumeris after exposure to Is-day residue s. In greenhouse trials, pyridaben showed significantly higher residual tox icity to all beneficial species than avermectin bl. Pyridaben had high resi dual 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 bl was slightly toxic or nontoxic to the predaceous mites A. cucumeris, A. degenerans, and P. pe rsimilis. Toxicity of avermectin b1 to E. formosa, A. colemani, D. sibirica , and O. insidiosus rapidly decreased to <25% mortality 6 days after applic ation. Eased on the results of the greenhouse trials, avermectin bl was con sidered suitable for use with predacious mites and could be combined in int egrated pest management (IPM) programs with other beneficial species after residual toxicity is taken into consideration. Pyridaben can also be combin ed in IPM programs with A. cucumeris, O. insidiosus, and D. sibirica after a 6-day residual period. (C) 2000 Academic Press.