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red spheres were used by only a handful of Michigan growers to monitor fly activity, 

 and most spraying had ceased by early to mid-August. This combination of events 

 undoubtedly explains the maggot fly problem which occurred in Michigan. It should 

 serve as a reminder to us that the comparatively little effort required to emplace and 

 examine red spheres for monitoring maggot fly abundance can pay very large dividends. 



Eastern and midwestern growers are not the only ones who must be concerned 

 with apple maggot. In 1979, a homeowner near Portland, Oregon brought some rotting 

 apples to the local extension service which were diagnosed as being heavily infested 

 with apple maggot larvae. Subsequent trapping and fruit injury surveys on the west 

 coast showed that apple maggot is more or less continuously distributed from southern 

 Washington to northern California. Numerous wild apple and hawthorn host trees in 

 presently infested areas appear capable of supporting substantial fly populations. 



Just how far the fly can penetrate into the major apple growing regions around 

 Yakima and Wenatchee in Washington is uncertain. The very dry summers in the 

 Washington state fruit growing areas coupled with the relatively low numbers of wild 

 host trees, are factors arguing against the widespread establishment of apple maggot 

 much beyond the northern border of Oregon. Nonetheless, a concerted and expensive 

 effort is now underway to maintain a buffer (fly-free) zone around the present infestation 

 area in Washington to prevent any further northward movement. The buffer zone, about 

 15 miles wide, is trapped heavily (50-80 traps per square mile) for maggot flies. Imidan 

 is sprayed extensively in locales surrounding sites of trap captures. In addition, there 

 is an intensive host tree removal program within the buffer zone. 



In Oregon, the apple maggot is now so entrenched (it may have been there, 

 undetected, for 10-20 years prior to 1979) that no feasible means exists of exluding it 

 from the vicinity of any of the apple growing areas. However, buffer zones, similar 

 to those in Washington, have been erected immediately around certain locales of intensive 

 apple growing, such as the Hood River Valley. 



Possibly California apple growers believed the fly would never be so bold as to 

 move south across the Oregon border. But on August 24, 1983 the first flies were detected 

 in traps about 50 miles into California. Within 2 months, the area of known infestation 

 reached about 150 miles south into California. Actually, it shouldn't be surprising that 

 the apple maggot was found in California. During the past 30 years apple maggot (in 

 the form of larvae in infested fruit) was intercepted by Border Station Inspectors more 

 often than any other insect pest entering that state. 



In mid-October, 1983 1 was asked to chair a panel of scientists to go before officials 

 of the California Department of Agriculture, growers, and the public to make 

 recommendations as to what to do about this "sudden" invasion of the fly. Because 

 of the near hysteria caused by the Mediterranean fruit fly invasion of California in 

 1981, 1 was very reluctant to accept this charge. But it proved to be a highly informative 

 and relatively calm experience. 



Our panel concluded that the apple maggot fly had probably been in California 

 for at least 5 years. Scouts were finding it nearly everywhere they looked, although 



