- 6 - 



Because of this exposure, A. fallacis eventually developed resis- 

 tance to certain organophosphorous Tiisecticides . Portions of our 

 orchard survey, described below, were undertaken in hopes of dis- 

 covering this particular predator in Massachusetts orchards. 



Last spring, we began intensive tri-weekly sampling of mite pop- 

 ulations from March through October in the orchard at the Belcher- 

 town Research Center, and in 6 commercial and 3 abandoned orchards 

 in 3 different locations across the state. In the Belchertown orch- 

 ard, each of the materials Zolone*, Guthion*, Imidan*, and Sevin* 

 were regularly applied by airblast sprayer to each of 3 groups of 

 trees, with 3 groups left unsprayed for comparison. Among the com- 

 mercial orchards, 3 used one type of spray program, while the other 

 3 used a different program. In each orchard, samples were taken of 

 the ground cover under the trees, bark, and leaves of 3 'Red Delici- 

 ous' and 3 'Mcintosh' trees. The ground cover and bark were sam- 

 pled to determine if mite predators, especially A. fallacis , existed 

 in these habitats at different times of the season. 



Bark and ground cover samples were placed in funnels under 

 heat lamps which forced mites out of the samples into jars of pre- 

 servative placed at the bottom. Leaf samples were brushed in a 

 mite brushing machine, the mites landing on glass discs on which 

 they could be readily observed. All mites were counted, including 

 red and two-spotted spider mites, tiny apple rust mites, and preda- 

 tory mites and insects. 



We also sampled the leaves of 20 other commercial orchards 

 from which we had obtained the spray history. This sampling was 

 conducted only once--at the peak of the mite season in August. 



Our results to date reveal arboreal mite predators to be widely 

 distributed in Massachusetts apple orchards. However, Stethorus 

 punctum , the black lady beetle important in Pennsylvania apple orch- 

 ards , and Typhlodromus pyri , the predatory mite important in Western 

 New York, were not found in our survey. The situation in abandoned 

 orchards was quite different from commercial ones. In commercial 

 orchards, fewer kinds of mite predators were found, the predominant 

 species being A. fallacis . This predator was seldom encountered in 

 abandoned orchards'!! Red and two-spotted mites were virtually ab- 

 sent in abandoned orchards, which is not surprising in view of the 

 high predator populations found there. Growth of these populations 

 was likely aided by high abundance of one of their food sources, 

 the apple rust mite. 



In many commercial orchards where the spray program included 

 repeated applications of Zolone* and/or Benlate*-glyodin combination 

 arboreal mite predators were scarce or totally absent. It appears 

 that one or all 3 of these materials may have been toxic or repel- 

 lent to the predators. In such orchards, the two-spotted spider miti 



*Trade name 



