14. 



than the statewide average percent TPB injury in IPM or Check 

 blocks (1.44%). This variation in TPB injury probably relates 

 simply to differences in pest pressure rather than any direct 

 treatment effect. 



Injury to fruit from several of the major insect pests (PC, 

 EAS, AMF, LR and GFW) was at acceptable levels, with no outstanding 

 differences between treatment blocks (Table 1). However, SJS 

 injury was higher in the alternate middle blocks in 1980, indicat- 

 ing the need to thoroughly apply dilute rates of oil in an every 

 middle treatment regime in 1981 to prevent further buildup of this 

 pest . 



It is interesting to note that both the percent of leaves 

 infested with aphids and the average number of plant- feeding mites 

 per leaf were lower in alternate vs. every-middle blocks in spite 

 of reductions in pesticide use in these blocks. 



Cost-Benefit Analysis 



In 1980, alternate-middle spraying resulted in a savings of 

 $53.22 per acre for insecticide and miticide materials and $12.41 

 for application costs. In addition, fruit loss due to insect 

 injury was $10.72 less per acre in alternate vs. every middle 

 blocks (Table 2) . 



Table 2. Cost-benefit analysis of every middle vs. alternate 

 middle treatments, 1980z. 



Dollor cost/acre 



Every middle Alternate middle Differences 



Avg. cost of insecticide 



and miticide materials $156.72 $103.50 -$53.22 



Avg. application costs 32.22 19.82 - 12.41 



Avg. value of fruit loss 



due to insect injury 61.36 50.64 - 10.72 



Avg. net benefit from alternate-middle spraying for 



insects and mites +$76.35 



- 



Based on suggested retail pesticide costs published by J. Williams, 

 Regional Fruit Specialist: labor costs of $5.50 per hour, fuel 

 costs of $2.20 per acre and average yields of 550 bu/acre. 



It is interesting to note that in 1980, alternate middle pro- 

 gram costs were not exactly one half of those of every middle pro- 

 gram costs. This is due to the fact that two growers applied oil 



