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Researchers Discover Destructive Fruit Fly Now in Maine

University of Maine Cooperative Extension fruit and pest management specialists monitoring for a particularly destructive non-native fruit fly have discovered its presence at five locations in Maine.

Now they are hurriedly collaborating with counterparts across the country to collect and collaborate on the latest research on the tiny, spotted-wing Asian fruit fly in an effort to protect 2012 crops. The Drosophila suzukii fly poses a serious threat to Maine fruit growers’ blueberry, strawberry, raspberry and potentially other soft-skinned fruits and possibly even vegetables, according to Jim Dill, Extension educator and pest management specialist in Orono.

“Our concern is if you get the spotted wing drosophila in low-bush blueberries — 50,000 acres — it would be disastrous, just devastating to our current Integrated Pest Management program and the crop,” Dill says. “And it’s a question of when.”

Maine’s blueberry harvest in 2011 exceeded 80 million pounds. Crop value is estimated at about $190 million, with a statewide economic impact of more than $250 million.

Dill and Extension blueberry researcher Frank Drummond have been monitoring fruit fly traps around the state looking for early detection of the fly that comes from Asia and has spread in the last four years from California to states in the northern and southern United States. They discovered it in September 2011, and Dill says he has trapped them now in five locations in Maine — in a tomato greenhouse in Berwick, raspberries in Limington, Newcastle and Monmouth, strawberries in Farmington and most likely, though unconfirmed, in high-bush blueberries in Clinton.

The Asian fruit fly is particularly destructive because, unlike common fruit flies, which lay eggs only in over-ripe, rotting or fermenting fruit, the spotted-wing Asian fruit fly has a serrated appendage — an ovipositor — used in egg-laying that saws through the soft skin of ripe and unripe fruit to deposit its eggs inside the fruit, according to Dill.

“It’s just as prolific as the vinegar (fruit) fly you find on your bananas, but those guys only attack overripe fruit,” he says. The Asian fruit fly “is now out there attacking unripe fruit hanging on the vine.”

Pesticide sprays are the only known control method, says Dill, but applications are expensive and must be done at least once a week, as opposed to a few times a year as determined through monitoring for current pests. Fall raspberry growers often never spray their fruit at all, and at least one grower informed Dill that he’ll get out of the business before applying the necessary sprays.

“We’re looking to see if there are any natural controls for it,” he says. “We’ve been working for years to try to reduce applying pesticides. It’s going to be expensive if you have to spray every week, and there could be unintended consequences of spraying every week. Everybody’s now trying to run and do the research.”

The flies can be transported in shipments of fruit and vegetables and even blown by strong winds.

“You figure it got to Maine from California in four years,” Dill observes. “Only four years to make its way completely across the U.S.”

Contact: Jim Dill, (207) 581-3879

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