Table 2. Appearance of exit holes of apple maggot larvae in Crataegus 

 mo 1 1 i 5 hawthorn drops. 



DATE OF W. DROPS IN WHICH A LARVAL EXIT HOLE 



DROP PICKUP DROPS APPEARED ON DAY OF DROP PICKUP 



NO. %_ 



Sept. 15 9^ 



19 90 



23 305 38 12 



27 206 Ith 21 



Oct. 1 295 86 29 



4 99 29 29 



8 25 4 16 



12 7 _2 29 



TOTAL 1121 203 l8 



What conclusions can be drawn from this work? By and large, our 

 results do indeed confirm the findings of the earlier researchers in that 

 picking up dropped fruit twice per week in commercial apple orchards is an 

 effective method of preventing entry of apple maggot larvae into the soil. 

 In fact, our results suggest that in nearly all situations, picking up drops 

 once per week should be sufficient. Only in cases where the variety is an 

 exceptionally early maturing one (for example. Early Mcintosh), and where 

 harvest of on-tree fruit is delayed well beyond the optimum for good commer- 

 cial quality, should it be necessary to pick up drops as often as every 3-4 

 days. Even then, use of sticky sphere; to capture the adults should reduce 

 larval infestation to such a low level that larval exit from fruit could be 

 delayed beyond that observed in this study. We speculate that this could be 

 so on the basis that the comparatively earlier exit of larvae after fruit 

 drop from C_^ mo 1 1 i s hawthorn trees than after fruit drop from Early 

 Mcintosh trees may have been in response to the more limited fruit flesh 

 resources of the hawthorn fruit (about 1/2 inch diameter) than the Early 

 Mcintosh apples (about 1 1/2 inches diameter). In other words, we postu- 

 late that under conditions where larval infestation is low and fruit size is 

 moderate or large, as ought to be the case in a commercial apple orchard in 

 which sticky spheres are used, larval exit from dropped fruit may occur 

 later than where larval infestation is high or the fruit is exceptionally 

 sma 1 1 . 



Further research is needed to evaluate this speculation and to deter- 

 mine the optimum frequency of apple drop pickup under existing California 

 orchard conditions. For non-pesticide-using apple growers in Massachusetts, 

 the combination of trapping with sticky red spheres and picking up maggot- 

 infested drops once per week should very effectively prevent any apple 

 maggot buildup, though it will not prevent entry of immigrating flies from 

 outside the orchard. 



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