Those which used two or fewer appUcations of 

 benzimidazole fungicides, whose detrimental 

 effects on mite predators are not agreed upon 

 universally, likewise were classified as "soft" 

 programs. Due to seasonal variability of spray 

 programs, blocks were reevaluated yearly and 

 reclassified by the tjT)es of pesticide used during 

 the previous production season. In total, the 

 study included 14 orchards using "hard" pro- 

 grams and 14 using "soft" programs. 



In 1988, the "hard" program resulted in 

 slightly higher infestations by European red 

 mite than did the "soft" program (Table 1). The 

 relationship, however, varied with saimpling 

 date, i.e. for some sampling dates, "hard" pro- 

 grams had more European red mites, and for 

 other dates, "soft" programs had more. Spray 

 program had no impact on the amount of Euro- 

 pean red mites present in 1989. The lack of a 

 difference in 1989 likely was due to an aggres- 

 sive spray program directed at mites in "hard" 

 blocks which kept plant-feeding mite numbers 

 comparable to those in "soft" blocks in spite of 

 lower predator numbers. 



The "hard" spray program resulted in sig- 

 nificantly more two-spotted spider mites than 

 the "soft" program in 1989, but in 1988, there 

 was no difference between programs (Table 1). 

 The first sample in 1989, however, found fewer 

 two- spotted spider mites in the "hard" program 

 orchards than in the "soft" ones. Because of the 

 differences fi"om year to year and the lack of a 

 consistent relationship between programs, even 

 when significant differences were noted, we can- 

 not state conclusively that numbers of two- 

 spotted spider mites were related to spray pro- 

 gram in this study. 



"Hard" spray programs had a significantly 

 lower proportion of leaves infested with the 

 Phytoseiid predator Amblyseius fallacis in 

 1989,butnotin 1988 (Table 1). The relationship 



between programs, however, again varied with 

 sample date, as with European red mite and 

 two-spotted spider mite. Hence, these results 

 also must be considered inconclusive. 



Lack of consistent spray-program effects on 

 European red mites, two-spotted spider mites, 

 and A. fallacis may be related to the initial 

 grouping of spray programs, which considered 

 the use of limited applications of potentially 

 toxic benzimidazole fungicides as part of "soft" 

 programs. Other factors independent of spray 

 program, such as low prey numbers in previous 

 years or high overwintering predator mortality 

 in certain orchards, also could have affected 

 predator numbers. 



Results were more conclusive in the case of 

 the Stigmaeid Zetzellia mali, which was found 

 in significantly higher numbers in "soft" pro- 

 gram orchards in both 1988 and 1989 (Table 1). 

 Differences were maintained across all sam- 

 pling dates in both years. The more consistent 

 results are not surprising withZ. mali, because 

 this predator spends its entire life either on the 

 tree or at its base Eind consequently would be 

 expected to be affected severely by harsh chemi- 

 cal sprays. Differences in time of appearance of 

 Z. mali were particularly evident (data not 

 shown), with individuals observed in "hard"- 

 program orchards only in very low numbers on 

 the last sample round in 1988. In 1989, only a 

 single individual was found in a "hard" orchard 

 over all sampling dates. 



Although, some aspects of this study were 

 inconclusive, we believe that the results give 

 some confirmation that insecticides, fungicides, 

 and herbicides can affect densities of prey and 

 predatory mites in apple trees. A clear implica- 

 tion of this finding is that growers wishing to 

 enhance the numbers of endemic mite predators 

 should avoid materials which can adversely 

 affect them. 



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Fruit Notes, Fall, 1993 



