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Document Type

Peer-Review Article

Abstract

A survey was conducted to identify the types and relative abundance of predatory arthropods associated with Panonychus ulmi in 21 Ohio apple orchards. Mite populations were sampled by leaf brushing, and insects and spiders were sampled by limb jarring. A state-wide survey was conducted in early July and in late August 1992, and five blocks were evaluated periodically from May until August 1992 at one farm in central Ohio. Predatory mites were detected in only 27% of the blocks surveyed in early July, but in 74% of the blocks surveyed in late August. The ratio of predatory mites to motile P. ulmi was ~0.1 in 20% of blocks in July and in 26% of blocks in August. In commer­cial orchards, the predominant species was Neoseiulus (Amblyseius) fallacis (Acari: Phytoseiidae), but Agistemus fleschneri (Acari: Stigmaeidae) and Zetzellia mali (Acari: Stigmaeidae) were found in several blocks. In orchards monitored throughout the season, N. fallacis was rarely detected until July, and reached the highest density in August when P. ulmi was at a seasonal peak. Important predators of P. ulmi that were detected in limb-jarring samples were Stethorus punctum punctum (Coleoptera: Coccinellidae), green lacewings (Neuroptera: Chrysopidae), the black hunter thrips (Leptothrips mali; Thysanoptera: Phlaeothripidae), and the insidious flower bug (Orius insidiosus; Heteroptera: Anthocoridae). No regional differences were observed in types of predatory mites or insects; the same types were found in all parts of Ohio.

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