Spotted wing drosophila pressure eases

An Asian fruit fly, spotted wing drosophila, is down in number so far this season in Central Washington which probably indicates a lighter year.
Dan Wheat

Capital Press

Published on July 1, 2014 2:40PM

WENATCHEE, Wash. — Spotted wing drosophila may be less prevalent in Central Washington cherries and stone fruit than it was last season.

That seems to be the case, based on early trap counts, says Elizabeth Beers, entomologist at the Washington State University Tree Fruit Research Center in Wenatchee.

“It’s great for growers to have clean crops,” she said.

Only 12 flies were caught between April 1 and June 19, which is less than last year and indicates populations just aren’t coming back, Beers said.

There were 332 caught between Jan. 1 and April 1 with most being on a single day in January in a single trap in the Tri-Cities, she said.

Counts usually peak in October and November, which is well past harvest of cherries and stone fruits.

Beers said she’s not sure why populations may be down. Freezing weather hit the region in early December and early February. There was no severe freeze like the pre-Thanksgiving Day freeze of 2010 that reduced populations in 2011, she said.

This is the fifth year of trapping in Central Washington. Trap counts exploded to 791,408 in 2013, up from 61,722 in 2012, due to a proliferation of the pest, a change in the style of trap and more bait being used, Beers has said.

There are fewer traps this year — 260 compared to 359 last year — because a collaborative collection program with company fieldmen ended, she said.

Trapping continues for an early warning of infestations and to track hot spots and overall pressure. It’s also being done to test which lures work best.

“We’ve had traps in some of the same places all five years, which gives a basis for comparison,” Beers said.

The Asian fruit fly was first detected in the U.S. in California strawberries in 2008. It moved into berries in the western parts of Oregon and Washington and into Central Washington cherries in 2010.

It has been kept under control with early detection and pesticides. It was a bigger challenge for cherry growers near Washington’s Tri-Cities and berry growers in the western sides of Oregon and Washington in 2013 because of increased numbers and multiple rains and winds making it hard to spray pesticides, Beers has said.


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