Damaging species of fruit fly found in Washington orchards

PASCO — A destructive species of Asian fruit fly that can ruin ripening soft fruit has been found in a Pasco orchard and another in Mattawa, a Washington State University entomologist said Wednesday.

A group of male and female spotted-wing drosophila, a type of red-eyed vinegar fly, were found last week in a trap set in a semi-abandoned apricot-tree orchard in Pasco, said Doug Walsh, who is with WSU's Irrigated Agriculture Research and Extension Center in Pasco.

A single male spotted-wing drosophila also was found near the sewage-treatment plant in Prosser, and an infestation has been confirmed in a cherry orchard in the Mattawa area, Walsh said.

One also was captured in Douglas County.

Walsh sent an e-mail to growers to confirm the presence of a pest feared because it can deposit eggs in and feed on ripening fruit, causing it to rot.

Eating fruit infested with eggs or damaged by the pest will not make a person sick, Walsh said.

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

"It's a concern," Walsh said. "But it's important to note that while it's here, it's not everywhere."

WSU researchers are using a $1.2 million U.S. Department of Agriculture grant to trap, study and test pesticides to combat the spread of spotted-wing drosophila. It is a menace to fruit because females have a larger-than-average egg injector, which allows them to lay eggs in fruit that is ripening.

Hundreds of traps have been put out in the region since late February. Nothing was found until recently, however.

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

Cherry harvest largely is over in the region. But other crops such as blueberries are being harvested "and there's a whole lot of Concord grapes out there," Walsh said.

The confirmation of spotted-wing drosophila came as no surprise to Alan Schreiber, director of the Washington Blueberry Commission.

Growers have been watching for the insects, which have red eyes and pale brown or yellowish-brown bodies.

"At this point it doesn't appear to be widespread," Schreiber said. "We know we can control them, so it won't end up being a problem as much as an (added) expense."

The flies came from Asia — Japan, Korea and China — and were introduced into California in 2008, likely through produce imported from Hawaii, Walsh has said.

They have since migrated up the coast to Oregon and Western Washington.

They can be controlled with a number of pesticides, but not completely eliminated in a growing season, Walsh said.

Spotted-wing drosophila have a number of preferred hosts, such as blackberries, and also can find alternative hosts in such fruits as apricots or peaches, he said.

Eastern Washington's dry climate, coupled with cold winters and hot summers, ultimately could help prevent their spread, he said.