The use of volatile baited traps will enhance the monitoring of apple maggot fly host race populations in nature to better determine the source of late-season infestations in apple orchards.

The apple maggot fly is a major cause of damage to commercial apple production in the Northeastern U.S. There is an increasing concern about late-season infestations and the source of these populations from reservoirs in nature.

Cornell scientists discovered that the apple maggot flies infesting apple fruit and those infesting Hawthorn fruit, the native host of the fly prior to introduction of apples to north America, show a strong preference for different fruit volatile blends. The identified blends were shown to be attractive to the apple and hawthorn fly populations in the wild, offering an opportunity to study the activity of flies in nature where feral apple and hawthorn trees are in proximity. Flies that infest orchards come from these reservoirs in nature, and it might be the case that late-season infestations in apple orchards, of increasing concern in the Northeast, are from hawthorn, or hybrid, populations and would not be susceptible to trap and kill techniques currently employed for control. Hybrid flies have been shown to be unresponsive to host fruit odors.

During the summer of 2005 traps were placed in a mixed stand of apple and hawthorn trees on a dairy farm in upstate New York. Season-long trapping results showed that apple maggot flies were present in the area, but were only captured in traps releasing the apple volatiles, whether the traps were in susceptible apple or hawthorn trees, both types containing abundant fruit, and evidence of maggot damage. The results raise questions about the distribution and interactions of the two host races in the wild. Future studies will investigate in greater detail, at three field sites, whether flies of both host fruit types are present, their host fruit odor preferences, and the possibility that hybrid flies exist in the wild.

• Other USDA (e.g., Water Quality, Special Grants, NRI)
• An undergraduate student from Hobart and William Smith Colleges, Geneva, NY, was sponsored by a Merck Grant to conduct the field project.

• Wendell Roelofs
• Harvey Reissig
• student to be named