Table 1. Abundance of mite predators on leaves sampled in September from first-level and 

 second-level IPM blocks in which T. pyri were or were not released in May of 1995. 



Results 



For T. pyri, the results (Table 1) show that 

 for the 1995 samples, small but detectable 

 numbers of this species were found in the 

 release blocks, but none were found in the non- 

 release blocks. For the 1996 samples, numbers 

 cf T. pyri in the release blocks averaged 

 considerably greater than they did in these 

 same blocks in 1995, suggesting that a buildup 

 of T. pyri had occurred. Almost no T. pyri were 

 detected in 1996 samples taken in the non- 

 release blocks. Interestingly, when data for 

 1995 and 1996 release blocks were pooled, 

 analysis indicated a significantly greater 

 average number of T. pyri in second-level than 

 in first-level IPM blocks. 



For A. fallacis, the results (Table 1) show 

 quite similar numbers of predators of this 

 species present in each t3rpe of block each year. 

 When data for 1995 and 1996 were pooled, 

 analysis indicated no significant difference in 

 average number of A. fallacis between second- 

 level and first-level IPM blocks. 



Examination of grower spray schedules 

 revealed that no insecticides other than 

 Guthion, Imidan, Lorsban, or Sevin (as a 

 thinner) and no acaricides other than oil. 



Omite, Apollo or Savey were applied to any 

 blocks during either year. None of these 

 materials is known to be harmful to T. pyri. We 

 believe that the significant negative effect of 

 first-level compared with second-level IPM 

 practices on the buildup of T. pyri was due to 

 fungicide use from early June onward in the 

 first-level blocks. Fungicides used after early 

 June included Penncozeb, Dithane, Ziram, 

 Polyram, Benlate, Topsin, and Captan. The 

 first four of these materials are known to have 

 detrimental effects on T. pyri. 



Conclusions 



Our findings indicate that by the end of the 

 growing season of the year following their 

 release, T. pyri mite predators appeared in 

 readily detectable numbers in nearly all blocks 

 in which they were released. The only 

 exception occurred in one of the six orchards, 

 where they were detected in neither of the 

 release blocks. This orchard received 2 

 applications of Dithane annually in May, which 

 might have impacted establishment of T. pyri 

 negatively. It appears from our results that 

 pesticides, particularly certain fungicides, have 



Frait Notes, Volume 62 (Number 2), Spring, 1997 



