POPULATION-DYNAMICS OF AMBLYSEIUS-FALLACIS (ACARI, PHYTOSEIIDAE) AND EUROPEAN RED MITE (ACARI, TETRANYCHIDAE) IN APPLE-TREES TREATED WITH SELECTED ACARICIDES

Experiments were conducted to evaluate the effects of early-season ovi cides, selective acaricides, horticultural oil, and potassium salts of fatty acids on the population dynamics of the phytoseiid predator Amb lyseius fallacis (Garman) and its prey, the European red mite, Panonyc hus ulmi (Koch). Both ovicides prevented early-season European red mit e outbreaks but only clofentezine-treated trees, with the help of A. f allacis, had low densities of European red mites throughout the entire season. However, treatment with clofentezine kept mites at subeconomi c levels only if insecticide sprays did not disrupt predator mite popu lations. Two applications of permethrin drastically reduced natural en emies, and allowed European red mite outbreaks to occur. Selective aca ricides varied in their effects on A, fallacis and European red mites. Although not significantly different from each other, all selective a caricides resulted in significantly fewer A. fallacis and European red mites than the untreated trees. Repeated applications of horticultura l oils and hl-Pede were required to reduce the European red mite popul ations and were no more effective in conserving predator mites than so me of the selective acaricides.