-17- 



Injury from the other major insect pests (plum curculio, San 

 Jose scale and apple maggot fly) was consistently greater in 

 every-middle than in alternate-middle blocks. European apple saw- 

 fly and green fruitworm injury levels were identical under both 

 treatments, whereas leafroller injury was high (0.58%) in one 

 alternate-middle block. 



Disease Injury to Fruit at Harvest 



Apple scab was the principal disease problem in all blocks. 

 Various rots were of secondary importance, while rusts were only 

 occasionally present (Table 1) . 



Overall disease incidence was slightly greater in every-middle 

 (0.381) vs. alternate-middle (0.23%) blocks. (For more information 

 concerning 1979 disease results in alternate-middle vs. every- 

 middle blocks, see Fruit Notes 44(6): 6-8.) 



Cost Benefit Comparison 



In 1979, alternate-middle spraying resulted in a savings of 

 $62.61 per acre for insecticide and miticide materials and appli- 

 cation costs. Fungicide materials and application costs were $70.69 

 less in alternate-middle blocks. Fruit loss due to insect and dis- 

 ease injury was $19.03 and $6.70 less, respectively, in alternate- 

 middle blocks (Table 2). 



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

 middle treatments, 1979. 



Dollar cost/acre 



Every- Alternate- 

 middle middle Differences 



Avg . cost of insecticide 



and miticide materials 



and application $125.23 $62.62 -$62.61 



Avg. value of fruit loss 



due to insect injury $ 78.93 $59.90 -$19.03 



Avg. net benefit from alternate-middle 

 spraying for insects and mites +$81.64 



Avg. cost of fungicide 



materials and application $141.38 $70.69 -$70.69 



Avg. value of fruit loss 



due to disease injury $ 17.80 $11.10 -$ 6.70 



Avg. net benefit from alternate-middle 

 snraving for diseases +$77.69 



Ave. net benefit from alternate-middle 

 spraying for insects, mites and diseases +$159.33 



