appears identical to A. fallacis even under a 

 powerful hand lens, can not be counted on at 

 this point to provide mite biocontrol in any but 

 a small minority of orchards. In an attempt to 

 establish T. pyri in additional orchards, we 



released hundreds of nymphs and adults (ob- 

 tained from Geneva, New York) in 1992 and 

 1993 in two orchards. Unfortunately, there is 

 no evidence to date that these releases have 

 resulted in estabUshment of T. pyri. 



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How Beneficial Are Pre-bloom Oii 

 Sprays Against European Red IVIites? 



Ronald Prokopy, Jennifer Mason, and Xingping Hu 

 Department of Entomology, University of Massachusetts 



For decades, most Massachusetts apple 

 growers have been applying pre-bloom oil sprays 

 against overwintering eggs of European red 

 mites. Just how beneficial to spring and sum- 

 mer mite control are these sprays? Further- 

 more, does the reduction in number of hatching 

 mites after spraying oil cause our principal mite 

 predator, Amblyseuis fallacis, to leave apple 

 trees in search of more prey elsewhere? 



To answer these questions, in 1993, we 

 cooperated with commercial growers in con- 

 ducting a test in two-acre blocks of apple trees in 

 each of nine orchards. Half of each block re- 

 ceived no oil or other miticide through May. The 

 other half received two applications of oil: one 

 during half-inch green to tight cluster and the 

 other during tight cluster to early pink. Each 

 application was at a rate of about one gallon of 

 oil to 100 gallons of water, with 100 to 300 

 gallons of water used per acre. Duiing the third 

 week of May, following egg hatch, 200 leaves 

 per untreated and treated block were examined 

 for presence of motile red mites and A. fallacis. 



In the untreated blocks, an average of 35% 

 of sampled leaves had motile red mites com- 



pared with an average of only 5% in the oil- 

 treated blocks (an 86% reduction in mite num- 

 bers). Nearly all untreated blocks required 

 repeat applications of miticide beginning after 

 petal fall. None of the treated blocks required 

 miticide apphcation until July or August. In 

 two sampled blocks that received only a single 

 pre-bloom application of oil, numbers of motile 

 mites were reduced 45% compared with un- 

 treated blocks. 



No A. fallacis were found on any of the 

 blocks in leaf samples taken before oil applica- 

 tion began in April or during May, although by 

 August, all of the blocks had at least some A. 

 fallacis. Evidently, cold winter temperatures 

 reduced populations of A. fallacis to such low 

 levels that it was inconsequential whether or 

 not red mite prey were low or high in numbers 

 in May. 



We conclude from these 1993 tests that two 

 pre-bloom applications of oil against red mite 

 eggs pay high dividends in suppressing red mite 

 populations through spring and early summer, 

 and in some years, possibly through the entire 

 growing season. 



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Fruit Notes, Spring, 1994 



11 



