-20- 



This latter analytical component likely introduces substan- 

 tial error in 1981, a crop year when growers throughout the state 

 are reporting better than normal packout percentages (i.e., relative- 

 ly few fruit being culled for insect or disease injury, poor color 

 or poor size). Recent work of Bahn, et al . ( Fruit Notes 46:3) shows 

 that only about a third of insect injured fruit observed in on-tree 

 harvest surveys actually ends up in the cull bin. As a consequence, 

 we believe that the "avg. value/A of fruit loss due to insect injury' 

 parameter should not be weighed as heavily as it is here, and that 

 the cost benefit analysis should principally reflect differences in 

 spray application and pesticide material costs. 



Pesticide Use and Insect Injury, 1977-1981 . 



Figure la details trends in Insecticide use in IPM and check 

 blocks since the onset of the Massachusetts' Apple IPM program. 

 These data indicate that while check insecticide use has remained 

 relatively constant at or near 1977 levels, IPM growers (all 1980 

 IPM data from 18 good cooperator blocks) have substantially reduced 

 the number of dosage equivalents of insecticide used in their 

 orchards, averaging about 30% fewer such sprays during the four 

 year period noted. 



A similar pattern is evident in Figure lb, with IPM orchards 

 registering about 601 fewer dosage equivalents of miticide used 

 in comparison to the checks. Check blocks nonetheless showed a 

 slight downward trend in miticide usage over this period as well. 



Such savings were not made at the expense of fruit quality, 

 however. Figure Ic indicates about 201 less permanent type fruit 

 injury in IPM blocks vs. the check overall, with IPM blocks sustain- 

 ing less average injury than the check in 3 out of the 4 years. 



Fruit injury resulting from aphids has been relatively unimport- 

 ant during the period cited (Figure Id) with a steady downward trend 

 evident in IPM and check blocks alike. 



