blocks. This result demonstrates the effectiveness of bor- 

 der row sprays in preventing penetration of these fruit-in- 

 juring pests into the block interior. 



Unfortunately, mite predators were low in frequency 

 in border-row-sprayed blocks in 1988, as they were in 1987. 

 Indeed, in neither year in neither type of block was the 



ratio of leaves with predators to leaves with pest mites 

 better than 1 to 15. This result suggests a very low proba- 

 bility of achieving effective biological control via buildup of 

 predatory mites in border-row-sprayed blocks (assuming 

 the 6 blocks in which our tests were conducted are repre- 

 sentative). From recent work in our department on the in- 



Table 3. Effects from using border row sprays with mite predators releases. 



Year Block No. 



Avg. no. AMF 



on interior 



monitoring 



traps 



Avg. % fruit injury 



by insect pests 



active after mid-June'* 



AMF CM RBLR Other 



1988 Brd-row- 



sprayed 6 

 Fully- 

 sprayed 6 



135 0.4 0.1 



104 0.2 0.1 



Avg. % leaves (or terminals) infested/block''' 



Ratio of 

 pest to 

 ERM predatory 



TSM AF YM mites WAA WAL PL LM GAA GAAP 



^500 on-tree fruit/block sampled during July, August, and September. 

 >'AMF = apple maggot fly, CM = codling moth, RBLR = redbanded leaf roller, ERM = 

 European red mites, TSM = two spotted mites, AF = Amblyseius fallacis, YM = predatory 

 yellow mites, WAA = woolly apple aphid, WAL= white apple leafhopper, PL= potato 

 leafhopper, LM= leafminer, GAA= green apple aphid, GAAP= green apple aphid preda- 

 tors: cecidomyiids and syrphids. 

 "400 leaves (or terminals) sampled/block during July, August, and September. 



