was the principal mite pest and miticides were applied repeatedly 

 (2-4 applications) for its control. Two-spotted populations first 

 appeared in early June, increasing thereafter until miticides were 

 applied in July and August. 



In comr.ercial orchards where the above materials were not used, 

 arboreal mite predators, particularly A. fallacis , were present in 

 numbers sufficient to exert some suppressive effect on the spider 

 mites. In most such orchards, the predominant mite pest was the 

 European red mite. In 2 of the intensively studied orchards, pop- 

 ulations of red mite peaked in late June in one orchard and late 

 July in the other. In each case, only one miticide application 

 was needed. A. fallacis (which appears to be only slightly suscep- 

 tible to the principal miticides used in all sample orchards: Plic- 

 tran* and Omite*) first appeared in the trees in July and increased 

 thereafter in apparent response to increasing European red mite pop- 

 ulations. The miticides undoubtedly eliminated part of A. fallacis ' 

 food source but apple rust mites were present in sufficient numbers 

 to provide alternate food. In the third orchard studied intensively, 

 spider mites never reached numbers high enough to cause damage and 

 no miticide was needed. 



None of the arboreal mite predators, including A. fallacis , 

 appeared in the bark samples, suggesting wind dispersal as the pri- 

 mary means of their getting into the tree. The ground cover samples 

 are still being analyzed. When completed, this analysis should 

 tell us more about the early season habits of these mite predators. 



We are encouraged by the wide distribution of certain arboreal 

 mite predators such as A. fallacis in Massachusetts apple orchards. 

 However, results to date tend to confirm our suspicion that these 

 important predators either cannot survive or are repelled in orch- 

 ards sprayed with certain insecticides and/or fungicides. This is 

 of immediate economic importance to the grower, and may have serious 

 long-term consequences as well. For example, if spider mites ever 

 become resistant to all available miticides (which is a possibility), 

 orchardists using these materials will almost certainly have little 

 protection against spider mite buildup. In orchards where the build- 

 up of mite predators is not discouraged, it is likely that miticide 

 usage can be reduced in most cases. 



During the next two years, we will be continuing our field and 

 laboratory studies so that we may more fully comprehend the poten- 

 tail of natural enemies, particularly mite predators, in the suppres- 

 sion of red and two-spotted spider mites in our commercial orchards. 



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