Establishment and Spread of Released 

 Typhlodromus pyri Predator Mites in 

 Apple Orchard Blocks of Different 

 Tree Size: 1999 and Final Results 



Ronald Prokopy, Starker Wright ,and Jonathan Black 

 Department of Entomology, University of Massachusetts 



Jan Nyrop, Karen Wentworth, and Carol Hering 



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



As discussed by Nyrop in the Winter 1 999 issue of Fruit 

 Notes, the predatory mite Typhlodromus pyri can be highly 

 effective in providing season-long suppression of pest Eu- 

 ropean red mites in commercial apple orchards. Unfortu- 

 nately, T. pyri has been found present (in numbers large 

 enough to be detected) in fewer than 10% of Massachusetts 

 orchards sampled since 1 978. In contrast, the predatory mite 

 Amblyseius fallacis has been found present in readily de- 

 tectable numbers in about 90% of Massachusetts apple or- 

 chards sampled since 1978. However, A. fallacis is less ca- 

 pable than T. pyri of enduring cold winter temperatures, 

 withstandmg low relative humidities, and surviving periods 

 of short supply of pest mites as food. 



In 1997, we initiated a program of introducing T pyri 

 into eight commercial apple orchards in Massachusetts in 

 which It was not previously detected. Two of our aims were 

 to ( 1 ) chart the rate at which T. pyri spread from trees on 

 which they were released to other trees in the same orchard 

 blocks, as affected by tree size and planting density, and (2) 

 determine the impact of T. pyri on pest mite populations. 

 Our study was intended to extend over a period of 3 years. 

 Ill the Fall 1997 and Winter 1999 issues of Fruit Notes, we 

 reported, respectively, on our findings from 1997 (the first 

 year) and 1998 (the second year). Here, we report on our 

 findings from 1999 (the third year) and our final conclu- 

 sions. 



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 hann to T pyri were to be used. These included 

 synthetic pyrethroid insecticides (at any time) and EBDC 

 fungicides (after mid-June). In addition, after mid-June, no 

 insecticide of any type was to be used, and captan or henomyl 

 were the only fungicides to be used. There was no restric- 

 tion 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 (seven rows of seven trees per 

 row) and of the cultivars Mcintosh, Empire, or Cortland. 

 Third-level 1PM is similar to second-level IPM in its focus 

 on using biologically-based pest-management practices, but 

 it embraces integration with horticultural concerns (such as 

 tree size) as an added component. 



T pvri were released onto the center tree of each thud- 

 level IPM block in May of 1997, in the manner described in 

 the Fall 1997 issue of Fruit Notes. No T pyri were released 

 in first-level 1PM blocks. Three times during the summer of 

 1997 and four times during the summer of each of 1998 and 

 1999 in each of the 48 blocks, we sampled 25 leaves from 

 the center tree, 15 leaves from each of the two outer-most 

 trees in the center row, and 15 leaves each from the center 

 tree in each of the two outermost rows. The leaves were 

 sent by overnight mail to Geneva, New York for the identi- 

 fication and counting of pest and predatory mites. In all, 

 more than 12,000 leaves were sampled in 1997 and more 

 than 16,000 in each of 1998 and 1999. 



Results 



Results on establishment and spread of T. pyri for all 3 

 years (1997, 1998, and 1999) are presented in Figs. 1, 2, 

 and 3. The data show good establishment of T. pyri in 1997 



Fruit Notes, Volume 65, 2000 



