‘Devastating’ fruit fly has growers worried

PORTLAND – Farmers and researchers in the Northwest are racing to control an Asian fruit fly that first appeared last summer and ruined some late-season peach and berry crops.

The fly is known as the spotted wing drosophila and appears to have migrated from California, where it appeared in 2008. Some growers in Oregon reported losing 20 percent of their blueberry and raspberry crops and up to 80 percent of late-variety peaches, and the pest has also been detected in Western Washington.

Growers worry it could spread to the states’ valuable cherry crops, pears, prunes, plums and wine grapes. Working with crop consultants and university researchers, growers are trying to determine whether insecticides will control the flies.

“It’s the most devastating insect I’ve ever seen in agriculture,” said Stuart Olson, a farmer in Marion County, Oregon.

Olson, who raises cherries and peaches, shut down his peach orchard last summer after discovering damaged fruit. He estimates he lost the last 10 days of picking and at least 25 percent of the revenue he would normally expect from late-variety peaches.

“You couldn’t even find a good peach to go out and pick, they were multiplying so fast,” Olson said.

The fly is unusual because it attacks ripe and ripening fruit, while most fruit flies are attracted to rotting produce. Female flies, equipped with a saw-toothed ovipositor, cut into the fruit skin and lay eggs just below the surface. The pinprick damage goes undetected until the larvae hatch and begin feeding, and the fruit collapses in a gooey mess.

“The fruit looks great when you buy it, and it would totally disintegrate within three days,” said Vaughn Walton, who is heading a crash research project at Oregon State University.

The fly is prolific, capable of producing 10 generations of pests per crop growing season. The rapid reproduction could help the flies adjust to pesticides.

Entomologists in Washington observed the flies in blackberries through last fall, according to Washington State University’s extension program. Entomologists say it’s not clear how well the pest is adapted to Washington’s major fruit-producing regions in the Columbia Basin.

Jim LaBonte, an entomologist with the Oregon Department of Agriculture, said controlling the fly will be difficult, in part because so many Oregonians grow fruit and berries in home gardens and because wild blackberries thrive everywhere.