Evaluation of Amblyseius fallacis 

 Predatory Mites on Apple Trees One 

 Year After Their Release 



Margaret M. Christie, Ronald J. Prokopy, James Gamble, 



David Heckscher, and Jennifer Mason 



Department of Entomology, University of Massachusetts 



Last year we reported results of two years of 

 releases of the predatory mite Amblyseius fallacis in 

 first- and second-stage IPM blocks [Fruit Notes 

 55(1):12-16]. These demonstrated that effective 

 biocontrol is more likely with a release of about 

 67,500 adult A fallacis per acre than with a release 

 of only 22,500 adults per acre. In 1990, we examined 

 the ability of previously released A fallacis to over- 

 winter and provide control of pest mites in the first 

 year following release. To reduce the expense of 

 releasing tens of thousands of A. fallacis per acre, we 

 hoped that treatment would not need to be repeated 

 each year to achieve effective control. 



Methods 



During 1988 and 1989, we released predatory A. 

 fallacis in 2 blocks in each of 4 orchards. One block 

 was managed using first-stage IPM methods, apply- 

 ing pesticides based on the results of monitoring for 

 pests and predators. The second block was managed 

 according to transitional second-stage IPM prin- 

 ciples [Fruit Notes 55(1):9-12]. No insecticides or 

 miticides were applied to the interior of this block 

 after the final plum curculio spray in early June. 

 Border row sprays of Guthion™ or Imidan™ were 

 used every three weeks to control apple maggot fly, 

 and fungicides harsh to predatory mites (such as 

 mancozeb and benomyl) were avoided. 



In 1988, we released approximately 500 adult A. 

 fallacis beneath each of 7 trees in both first- and 

 second-stage blocks in the 4 orchards. In 1989, we 

 released approximately 1500 A. fallacis adults in the 

 foliage of each of 7 trees in the first and second stage 

 blocks. Predators were released when 20 to 40% of 

 the leaves in the first- and second-stage blocks were 

 infested with European red mites or two-spotted 

 mites. Sampling for pest and predatory mites took 

 place in June (before releases of predatory mites), in 

 July (shortly after A fallacis had been released), in 



August, and in September. 



In 1990, first-stage IPM management continued 

 in one block in each orchard. In the second-stage 

 IPM block, border row sprays for apple maggot fly 

 during July and August were replaced with sticky 

 red sphere traps placed around the perimeter of the 

 block. No mite predator releases were made in any 

 of the blocks. Sampling again occurred in June, 

 July, August, and September. 



Additionally, we monitored pest and predatory 

 mite levels in first- and second-stage blocks in 4 

 orchards each year which had not received A falla- 

 cis releases. In the second-stage blocks in these 

 orchards, sticky red sphere traps were used for AMF 

 control; no insecticide or miticide was applied to the 

 blocks after early June in any year. 



Results 



In the 4 orchards in which releases of A fallacis 

 occurred in both 1988 and 1989 (Table 1), the ratio of 

 pest mites to predatory mites averaged 8: 1 in second- 

 stage blocks and 9:1 in first-stage blocks after release 

 in 1988, suggesting that only moderate biocontrol of 

 mites could be expected. By late June of 1989, pest 

 mites had almost reached threshold levels for treat- 

 ment, and no A fallacis had been found. After 

 release of A fallacis in July of 1989, the ratio of pest 

 to predatory mites averaged 4:1. In September the 

 ratio of pest mites to A. fallacis was 2:1 in the second- 

 stage blocks and 1:1 in the first-stage blocks. These 

 ratios were highly favorable to biological control of 

 pest mites. During 1990, pest mite levels in these 

 orchards began to increase in July; by August, they 

 reached 46% of sampled leaves in second-stage 

 blocks and 36% of leaves sampled in first-stage 

 blocks. Despite their high levels at the end of the 

 1989 growing season, very few A fallacis were found 

 until late 1990. Not until September, after danger of 

 mite damage had passed, did the ratio of pest mites 



10 



Fruit Notes, Winter, 1991 



