A Model Study of Acaricide Resistance, Spider Mite Outbreaks, and Biological Control Patterns in Michigan Apple Orchards 1 , 2

Abstract

In experimental apple orchard plots where a nonselective acaricide had been intensively applied, patterns of acaricide resistance, control failure, and spider mite outbreaks were documented by toxicological and field-sampling experiments. Contrasting examples of effective chemical control associated with initial application of the chemical and effective biological control interactions where the chemical was omitted also were characterized. In each treatment interactions of the spider mites Panonychus ulmi (Koch) and Tetranychus urticae Koch with the phytoseiid mite predator, Amhlyseiustallacis Garman, were studied in orchard tree or ground cover habitats and related to the development of an effective spider mite control program in Michigan fruit orchards.