Inventory of Predacious Mites in Quebec Commercial Apple Orchards Where Integrated Pest Management Programs Are Implemented

The commercial apple (Malus spp.) orchard ecosystem in Quebec has a diverse fauna of predacious mites. A systematic 2-yr survey showed Amblyseius fallacis (Garman), Typhlodromus caudiglans Schuster (Acari: Phytoseiidae), and Agistemus fleschneri Summers (Acari: Stigmaeidae) to be the most abundant species. Other phytoseiids, Typhlodromus conspicuous (Garman), Typhlodromus herbertae Chant, Typhlodromus longipilus Nesbitt, Typhlodromus bakeri (Garman), Typhlodromus pyri Scheuten, Amblyseius okanagensis (Chant), and Amblyseius finlandicus (Oudemans), were found in low numbers. Two of these species, A. finlandicus and T conspicuus, were identified for the first time in Quebec. Other occasional species included Anystis baccarum (L.) (Acari: Anystidae) and Balaustium sp. (Acari: Erythraeidae). Tetranychid mite numbers were always less than two mites per leaf throughout the study, and none of the commercial orchards required an acaricide treatment. A notable aspect of this study was that seasonal totals for A.fleschneri and A.fallacis decreased 7.3- and 42.2-fold, respectively, whereas T caudiglans increased 9.1-fold from 1999 to 2000. Possible mechanisms for these changes, including variations in winter mortality, competition for food, and intraguild predation are discussed.