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Controlling Spider Mites in Massachusetts 

 Apple Orchards Through Conservation 

 of Predator Mites 



Roy G. Van Driesche, Ronald J. Prokopy, and William M. Coli 

 Department of Entomology, University of Massachusetts 



Introduction 



Spider mites (European red mite, Panonychus ulmi 

 (Koch), and two-spotted spider mite, Tetranychus urticae 

 Koch) have become increasingly significant pests in apple 

 orchards due to destruction of predator mite populations 

 and development of resistance to some major milicidcs. 

 While spider mites are not direct pests of the fruit itself, the 

 cost of their control has increased relative to control costs 

 of other pests. Efforts to reduce production costs 

 therefore must include less expensive alternatives for 

 spider mite control. This article discusses how the strategy 

 of predator conservation may be employed by growers to 

 reduce their mite control costs. 



The Predators 



In New England the most important mite predator is 

 the phytoseiid m'ltc, Amblyseiusfallacis (Garman) (Table 



1). A second species of importance is the stigmaeid mite, 

 Zetzellia mail (Ewing). In Western New York, 

 Typhlodromus pyri (Scheuten) rather than/l./o/Zacw is the 

 major phytoseiid predator and in Pennsylvania and New 

 Jersey, the coccincUid Stelhonis punctum (LeConte) is 

 important. 5. punctiim is most often seen as a predator 

 attacking high density mite populations (15 or more mites/ 

 leaO; whereas, A. fallacis does well moderate mite 

 densities (4 to 7/leaO. T.pyri andZ. mali are able to persist 

 at very low mite levels (under 3/leaO because of their 

 abilities to utilize various alternative food sources such as 

 rust mites, pollens, and fungi. Predator mite biology for 

 , each species must be understood if management practices 

 are to be effective. For example, whereas T. pyri spends 

 the entire year in apple Uccs,A. fallacis overwinters in the 

 orchard groundcover. Management of orchard 

 groundcover thus infiuences both A. fallacis survival and 

 the timing of its recolonization of apple trees the following 



season. 



