Good Fruit Grower / Web 2010 / Scientist works to ID maggots

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Scientist works to ID maggots

Dr. Wee Yee, entomologist with the U.S. Department of Agriculture in Yakima, Washington, is working on ways to distinguish apple maggot (which is a quarantine pest) from the almost identical snowberry maggot fly, which is not a pest of apple.

Yee said when trapping is done for apple maggot, sticky traps are often placed in hawthorn trees (which are a host of both species) or abandoned apple trees where snowberry bushes are in the vicinity. It would not be unusual to find a snowberry maggot fly on an unsprayed apple tree, even though it does not attack the fruit.

Yee believes that if the flies could be identified with 100 percent accuracy, apple orchards would never be mistakenly placed under quarantine status and unmanaged apple or hawthorn trees, which are a host for both insects, would not need to be treated unnecessarily for apple maggot if the insect is in fact the snowberry maggot.

He reported to the Washington Tree Fruit Research Commission, which is funding his research, that by analyzing the wing shape of the two species, a female apple maggot can be identified with 98.5 percent accuracy and a female snowberry maggot with 99 percent accuracy. The shape and length of the female’s ovipositor, and the shape of the male’s clasper (which is used to hold the female during mating) can also be used to help identify the species. A combined analysis of wing shape, ovipositor, and clasper should result in almost perfect identification of the species, Yee believes.

In practice, flies could be removed from sticky traps for identification, Yee said. He envisions that such an analysis could be done by the Washington State Department of Agriculture.