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THE APPLE MAGGOT IN MASSACHUSETTS, MICHIGAN AND WEST COAST STATES 



Ronald J. Prokopy 

 Department of Entomology 



Massachusetts apple growers are all too familiar with the apple maggot and the 

 type of fruit injury that this pest can cause. During our pilot integrated pest management 

 (IPM) program on apples in Massachusetts from 1978-1982, we used sticky-coated red 

 wooden spheres to monitor the time and extent of maggot activity in 16-60 commercial 

 orchard blocks each year. Without exception, at least a few maggot flies were captured 

 annually in each block. In some cases, several hundred were caught in a single block. 



Our experience shows that 99.9% or more orchard maggot fly populations in 

 Massachusetts originate from wild or abandoned host apple or hawthorn trees within 

 a few hundred yards of the orchard. On only 2 occasions have we found maggot flies 

 emerging from within a commercial orchard itself. In both of these, maggot-infested 

 early-maturing varieties such as Puritan and Astrachan were not harvested the previous 

 year. 



Despite the continuous pressure that maggot flies exert on our Massachusetts 

 orchards, only 0.08 and 0.09% of harvested fruit showed maggot injury in IPM and check 

 orchards, respectively, during the 5 years of the pilot IPM program [see FRUIT NOTES 

 48(3)]. The principal reason for this comparatively low fruit injury is the high sensitivity 

 of the adults to even low dosages of pesticide. Moreover, as shown by the work of Dr. 

 Harvey Reissig of Geneva, New York, some pesticides such as Guthion are highly effective 

 not only against the adults but also kill the eggs and young larvae, just beneath the 

 fruit skin. 



Our experience reveals that so long as growers rely on red sphere trap captures 

 to determine need and timing of maggot fly sprays, there is very little chance of any 

 injury occurring. Most of the maggot injury detected in Massachusetts has been on late 

 varieties such as Delicious and Golden Delicious in cases where substantial fly 

 immigration occurred 2 or more weeks after spraying ceased for the year. 



Michigan apple growers in 1983 experienced more apple maggot injury than at 

 any time during the past 2-3 decades. According to Michigan fruit entomologist Dr. 

 Gus Howitt, fruit of late varieties such as Jonathan had more than 5% maggot injury 

 in many orchards. Dr. Howitt told me that hundreds of thousands of bushels have been 

 rejected for fresh fruit market and for processing because of excessive maggot injury. 



Dr. Howitt attributed the severe maggot problem in Michigan in 1983 to the very 

 dry summer, which precluded summer emergence of flies from overwintering pupae. 

 Emergence didn't begin in full force until just after heavy rains in late August and early 

 September. By that time, most of the summer-maturing fruits on wild or abandoned 

 trees had fallen, thereby stimulating extensive immigration of flies into commercial 

 orchards. The warm September was favorable for fly egglaying in late varieties. Also, 



