Establishment and Spread of Released 

 Typhlodromus pyri Predator Mites in 

 Apple Orchard Blocks of Different Tree 

 Size: 1998 Results 



Ronald Prokopy, Starker Wright, and Jonathan Black 

 Department of Entomology, University of Massachusetts 



Jan Nyrop, Karen Wentworth, and Carol Herring 



Department of Entomology, Cornell University, NYSAES, Geneva, New York 



Studies in New York, other states, and other 

 countries have shown that the predatory mite 

 Typhlodromus pyri, where established, can be 

 highly effective in providing season-long suppres- 

 sion of pest European red mites in commercial 

 apple orchards. Three of the reasons why T. pyri 

 is more reliable than the mite predator Amblyseius 

 fallacis in maintaining pest mites below injurious 

 levels year after year are its better ability to endure 

 cold winter temperatures, its better ability to with- 

 stand low relative humidity, and its better ability 

 to survive periods of short supply of pest mites as 

 food (as may occur in springtime). In Massachu- 

 setts, A. fallacis has been found present in about 

 90% of commercial apple orchards sampled since 

 1978. In contrast, T. pyri has been found present 

 in numbers large enough to be detected in fewer 

 than 10% of Massachusetts commercial apple or- 

 chards sampled since 1978. 



In 1997, we initiated a program of introduc- 

 ing T. pyri into eight commercial apple orchards 

 in Massachusetts in which it was not previously 

 detected. Three of our aims were to (1) chart the 

 degree of establishment of T. pyri in each orchard 

 as affected by types of pesticide used; (2) chart the 

 rate at which T. pyri spread from trees on which 

 they were released to other trees in the same or- 

 chard blocks, as affected by tree size and planting 

 density; and (3) determine the impact of T. pyri on 

 pest mite populations. Our study was intended to 

 extend over a period of at least 3 years. In the Fall 



1997 issue of Fruit Notes, we reported on our find- 

 ings from 1997, the first year. Here, we report on 

 our findings from 1998, the second year. 



Materials & Methods 



As indicated in the Fall 1997 issue of Fruit 

 Notes, our experiment was conducted in six blocks 

 of apple trees in each of eight commercial orchards. 

 Of the six blocks per orchard, two each contained 

 trees on M.9, M.26, or M.7 rootstock, designated 

 as small, medium-size, or large trees. One block 

 of each pair received first-level IPM practices, 

 wherein growers applied insecticides and fungicides 

 of their own choosing and timing of application, 

 which extended from April through August. The 

 other block of each pair received third-level IPM 

 practices, wherein the initial intent was that no 

 pesticides known to cause a moderate or high level 

 of harm to T. pyrt were to be used. These included 

 synthetic pyrethroid insecticides (at any time) and 

 EBDC fungicides (after mid-June). In addition, 

 after mid-June, no insecticides of any type was to 

 be used, and captan or benomyl were the only fun- 

 gicides to be used. There was no restriction on 

 type of miticide allowable for use in third-level 

 blocks, except for Carzol, which was not used. 

 Each block was comprised of 49 trees (7 rows of 7 

 trees per row) and of the cultivars Mcintosh, Em- 

 pire and Cortland. Third-level IPM is similar to 

 second-level IPM in focus on using biologically- 



10 



Fruit Notes, Volume 64 (Number 1), Winter, 1999 



