Spotted wing fruit fly could devastate the Walla Walla Valley

Spotted Wing Drosophila is the enemy of wine grapes and other crops.


Scroll below to watch a video about the spotted wing drosophila.

WALLA WALLA -- It's no bigger than a preschooler's crayon dot but has the potential to cost the Walla Walla Valley $500 million in damages.

Clive Kaiser, head of Oregon State Extension Services office in Milton-Freewater, said Friday that five new sightings of the "spotted wing drosophila" fruit fly have been confirmed in the area during the past few weeks.

The flies, which are "the same size as the little midges you get above rotting bananas," are a common problem in California, Western Washington and Oregon, along with British Columbia, Kaiser explained.

Mild winters in those regions allow the pest to thrive -- indeed, the population has "exploded," Kaiser noted.

Seen in parts of Japan, Korea and China as long as eight decades ago, this particular fruit fly was unknown to the United States until it appeared in California in 2008. It was not present in Oregon until last year. However, in one growing season the pest has spread up, down and over the state, he said.

"Basically what happens is it gets introduced to an area, it comes in on fruit that is infected. It could be a commercial or an individual (operation). We're not pointing fingers now that we have it, we just have to deal with it."

The hope is the more severe winter temperatures here will be enough to kill overwintering spotted wing populations in the Walla Walla Valley, the extension agent said. "So the threat is expected to be from reintroduction of the pest to the Valley every year."

It is a significant threat. This prolific pest has the potential to be devastating to berry and grape crops, Kaiser noted. While other fruit flies lay eggs in the cracks and spots of soft or rotting fruit, the female Spotted Wing -- and she is not, in fact, spotted -- is uniquely equipped to attack green fruit in order to prepare a birthing bed.

Her ovipositor, an organ used for laying eggs, looks like the edge of a saw. She can open unripe fruit and tuck her one to three eggs. In a few days, the fruit has a visible, widening blemish that sometimes weeps juice, attracting bacteria and fungus.

The female spotted wing may lay as many as 300 eggs in her short lifetime and one growing season may see up to 13 generations of the pest. Oregon's Willamette Valley has had entire blueberry farms fall victim to the fly, Kaiser said.

The pest doesn't choose one fruit over another; instead it is a danger to all, he added. "It will move from cherries to blackberries to wine grapes. Quite a few concerned growers have been in my office to see me."

However, so far the fly has left the Valley's apple crop alone, he emphasized. "It's not been found to effect apples anywhere in the U.S."

Along the Columbia Gorge in Oregon, farmers in The Dalles region have been forced to drastically alter operations, spraying crops every five to seven days "religiously," the agent said. The increased time and chemicals add to the cost of farming, which can include whatever fruit is made unmarketable by the fruit fly.

Without timely intervention, the Valley's wine industry could be ruined, Kaiser added. "We need everyone to be vigilant in the Valley this fall."

Officials have been trapping the pests, sometimes catching as many as 14 in one trap.

Experts speculate local wild blackberries could become a delectable host to the Spotted Wing flies. "We fully expect eradication of wild blackberries to be a requirement in the future if the (pest) is to be controlled effectively," Kaiser said.

The news could be even worse, he added. "Fortunately our lucrative markets already have this pest, so that will not increase controls for exporting."

For more information: call 541-938-5597 or visit Oregon State University Spotted Wing Drosophila website


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