Fruit fly hasn't hit wine grapes

By Kevin McCullen, Herald staff writer August 13, 2010 

PROSSER -- A destructive species of Asian fruit fly has moved into backyard fruit trees in Prosser and some concord grape vineyards, but thus far has stayed away from Eastern Washington wine grapes, a Washington State University entomologist said Thursday.

An infestation of spotted-wing drosophila, a type of red-eyed vinegar fly, was found earlier this summer in a cherry orchard in the Mattawa area. Since then, the pest has spread to other areas of Eastern Washington, although an accurate assessment of its spread is not yet known, said Doug Walsh, who is with WSU's Irrigated Agriculture Research and Extension Center in Prosser.

Spotted-wing drosophila can deposit eggs in and feed on ripening fruit, causing it to rot. But eating fruit infested with eggs or damaged by the pest will not make a person sick.

Walsh spoke to wine and concord grape growers at WSU's annual Viticulture and Enology Day at the Prosser agricultural station.

Growers of soft fruits and agricultural officials have feared the pest's arrival in Eastern Washington from California and other regions because of its potential effect on the state's thriving fruit industry.

The insect is known to attack cherries, raspberries, blackberries, blueberries, strawberries, plums, grapes and nectarines.

"My initial fear is for the concords, but the jury is still out on wine grapes," Walsh said.

Spotted-wing drosophila also has been found in backyard fruit trees in Prosser and Pasco. It can be controlled with a number of pesticides, and Walsh recommended homeowners contact their local county extension officer to find out what insecticide can be used for different fruit trees.

He also suggested homeowners harvest fruit as soon as it ripens.

"The take-home message here is to not let fruit get overripe," Walsh said.

Ultimately, Eastern Washington's climate could prove too inhospitable for the pest to sustain itself long-term, he said. Spotted-wing drosophila don't do well in cold weather and may not be able to survive a cold snap, he said.

Climatically, Eastern Washington is "on the edge of where it should do well and shouldn't do well," he said.

Grape growers Thursday also inspected WSU's new research vineyard, where Markus Keller and his team of graduate students planted eight acres this spring primarily with merlot, riesling, chardonnay and cabernet sauvignon grapes.

Keller, a Chateau Ste. Michelle distinguished professor in viticulture, said 25 other varieties also were planted on outside edges of the vineyard, in part to test their cold hardiness in winter.

The new vineyard will allow WSU to broaden its research of wine grapes and their maturation "from the soil to the glass," Keller said.

WSU also will continue to use test plots in commercial vineyards. But the new vineyard will allow researchers to carefully chart grape growth and ripening, Keller said.

"Everything we do in the vineyard with grapes involves this: Will it make a difference in the wine?" said Thomas Henick-Kling, director of WSU's viticulture and enology program.

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