Fruit fly invades West Coast

PORTLAND, Ore. -- It's a tiny fruit fly with an exotic name and a taste for some of Oregon's most valuable crops. And since its surprise and destructive appearance last August, the state's leading entomologists have been engaged in a frantic, cra...

PORTLAND, Ore. -- It's a tiny fruit fly with an exotic name and a taste for some of Oregon's most valuable crops. And since its surprise and destructive appearance last August, the state's leading entomologists have been engaged in a frantic, crash course to find it, understand it and control it.

First found in Oregon late last summer, the spotted wing Drosophila has emerged as the most serious insect threat to high-value fruit and berry crops. It's too late, experts say, to wipe it out.

Here to stay

The spotted wing Drosophila -- Drosophila suzukii, to be formal -- is probably here to stay. Its arrival slams home the hard truth about the risk that accompanies international trade and travel. The more goods and people cross borders, the more likely invasive pests will come along for the ride.

The spotted wing is a native of Asia -- Japan's farmers have battled it since 1916 -- that appeared in California in 2008 and quickly migrated to Oregon and Washington. Named for the distinctive spot at the tip of males' wings, the fly is unusual because it attacks ripe and ripening fruit. Most fruit flies go after overripe or damaged produce.


The female, equipped with an unusual serrated-edge ovipositor, cuts into the skin and deposits one to three eggs. The eggs poke a pair of tiny breathing tubes through the surface and feed on the fruit from the inside as they develop into maggots. Within a few days, healthy fruit collapses into a gooey mess.

Katy Coba, director of the Oregon Department of Agriculture, calls it the "Dracula" fruit fly.

"It's so new that we're trying not to panic, but we're very, very concerned," she says.

With good reason. West Coast farmers produce 76 percent of the nation's raspberries, blackberries, strawberries and cherries. California researchers estimate that a 20 percent damage rate would cost West Coast farmers $511 million in lost crop value, including $31.4 million in Oregon.

One peach grower in Oregon's Marion County says damage to his late-variety peaches was nearly 100 percent, causing him to shut down his orchard 10 days early and costing him 20 to 30 percent of the revenue he normally expects.

Under attack

Within weeks of confirming the fly's presence in Benton County, Ore., last summer, researchers determined it had spread to 14 other Oregon counties, from Jackson County in southern Oregon, up the Willamette Valley to Portland and east up the Columbia Gorge to Hood River, Wasco and Umatilla counties. It was found in blueberries, raspberries, blackberries, strawberries, cherries, peaches, plums and grapes.

"You name the fruit, it will attack it -- that's the big problem," says Helmuth Rogg, supervisor of the state's pest management division.


Wine grape growers sustained minor damage last year, but most of the crop was harvested by the time the fly emerged, says Chad Vargas, vineyard manager for Adelsheim Vineyard in Newberg, Ore. Vineyards will have to be vigilant this year, as grapes are a likely host for the fly to breed in, he says.

"There will be an industry-wide effort in trapping to help monitor the thing," Vargas says.

The flies live only a couple weeks but are capable of producing 10 generations per season. The females are busy; one raised for study at a U.S. Department of Agriculture lab in Corvallis, Ore., laid 160 eggs in a single day.

"This particular pest is so prolific, so abundant, there's no way to get rid of it anymore. So we have to deal with it," Rogg says.

California came to the same conclusion. By the time it was detected there, "eradication was deemed impossible," researchers wrote in 2009.

Researchers and other officials think the fly came to Oregon in infested fruit, probably from California, which in turn got it from somewhere else. While international agreements require various inspections and treatment of fresh fruit exports, and travelers between states are supposed to surrender fruit at the border, the "rigorousness of inquiry and enforcement" remains a variable, says Scott Goddin, a U.S. Commerce Department official in Portland.

Mounting efforts

The flies, and their impact, are snowballing.


Florida officials reported finding the fruit fly shortly after Oregon did last summer. In February, the European Plant Protection Organization issued an alert for the bug, saying it had been found in Italy.

Australia recently warned that imported Oregon fruit must be fumigated with methyl bromide, and it wants proof that the treatment will kill spotted wing Drosophila. Some farmers may buy crop insurance to protect against damage this summer.

While standard insecticides will kill the fly, that means additional cost for growers and increased scrutiny by consumers. And certified organic growers are left in a lurch: they don't use sprays that conventional growers do, and it's not clear what will be effective for them.

Meanwhile, beehive owners who provide pollination service up and down the West Coast are concerned that an increased spray regimen will wipe out their bees.

To the rescue

Against that backdrop, a team of researchers and entomologists in Corvallis are pressing to understand and outwit the fruit fly.

It's research in a rush, carried out in sophisticated fly-rearing cabinets with light and temperature controls and outdoors with traps jury-rigged from plastic soda containers, a slosh of apple cider vinegar and sticky fly paper.

The team, drawn from Oregon State University and the U.S. Department of Agriculture, is trying to determine how well spotted wing Drosophila survived the winter, predict when it will emerge this spring and learn about its food preference, reproduction rates and life cycles.


Key team members are Amy Dreves, an OSU extension entomologist, Vaughn Walton from the university's Department of Horticulture and USDA researchers Denny Bruck and Jana Lee.

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