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Spotted wing drosophila appears in Spokane County for first time

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Matthew Weaver
The fruit fly pest spotted wing drosophila has been recorded in Spokane County for the first time. Washington State University Tree Fruit Research and Extension Center entomologist Elizabeth Beers said the pest is becoming more established each year, and spreading, but growers are learning to manage it. WSU Spokane County Extension urban horticulture coordinator Tim Kohlhauff is hoping for cold winter to help kill off the insect.

SPOKANE — A fruit fly pest that caused $500 million in damages in its first year in the Northwest has shown up in Spokane County for the first time.

Washington State University Extension urban horticulture coordinator Tim Kohlhauff said it’s the first time the spotted wing drosophila has been recorded in the county.

“What makes this pest stand out is that females are able to lay eggs in healthy, still-growing fruit,” Kohlhauff said. “Most fruit flies, the fruit has to be overripe or on the ground.”

The insect shows a preference for softer skin summer fruits, particularly cherries, Kohlhauff said.

“It doesn’t make the fruit inedible, but not many people are prone to (eating it),” Kohlhauff said. “It certainly lowers the quality and the saleability would certainly be impacted.”

It first appeared in 2009, moving up the coast from northern California along western Oregon and western Washington and into British Columbia. It has since shown up in Idaho.

It first appeared in eastern Washington in 2010, said Elizabeth Beers, entomologist with WSU’s Tree Fruit Research and Extension Center in Wenatchee. Spotted wing drosophila is becoming more established each year, she said, and is increasing its range.

Kohlhauff said one theory is that the pest entered the Spokane area on a produce truck, or larvae on fruit that was thrown out may have hatched, he said.

So far, the pest has only been found on homeowners’ backyard blackberries. It may have been introduced sometime early in the summer, Kohlhauff said, because the homeowners are reporting sightings only on later-season blackberries and raspberries.

The extension recommends homeowners make a trap, luring the insects with apple cider vinegar in a cup and a yellow sticky trap hanging over the cup. That way researchers can examine the insect anatomy to confirm it as spotted wing drosophila.

Beers said the first line of defense is pesticides. Other research efforts include development of biological controls like parasites to target the pest, or cultural controls like sanitation.

Kohlhauff recommends cleaning up fallen fruit, noting most occurrences have taken place within city limits.

Chemical treatments for spotted wing drosophila are continuous, compared to a one-time application for the cherry fruit fly, Kohlhauff said.

“As long as there’s fruit in the tree or on the shrub, they’re likely to be in there and reproducing,” he said.

Mild winters mean the insect is likely to survive.

“We’re hoping it doesn’t overwinter,” Kohlhauff said. “Normally it wouldn’t survive a cold Spokane winter; we need some temperatures to get down into the single-digits for a period of time to get rid of them.”

But Beers says the industry is becoming accustomed to managing the insect.

“I think this pest is here to stay, and we’ll learn to manage it and carry on,” she said.

For more information, contact Kohlhauff at 509-477-2172 or tkohlhauff@spokanecounty.org



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