Research not able to find where spotted-wing drosophila spends cold months

By MITCH LIES

Capital Press

Oregon State University Extension entomologist Peter Shearer said he still is catching spotted-wing drosophila in his traps in Hood River and Wasco counties, which shows the insect overwinters.

But experiments to determine where it resides during cold winter months have been unfruitful.

"It may be they are overwintering in crawl spaces in houses, maybe barns, maybe in duff," Shearer said.

Where the drosophila overwinters is one of many questions scientists hope to answer as research into the vinegar fly moves into its third year.

The fly, first was found in Oregon in the fall of 2009, "is a big threat for fresh-picked fruit and the processing market," Shearer said.

Shearer advised growers to trap and treat for the pest, beginning when fruit starts ripening.

"We know that the spotted-wing becomes attracted and starts damaging fruit when it becomes pink colored, so that is when the first spray should go on," he said.

"We recommend if flies are found in and around your orchard that you treat for them because the flies and the damage they cause can really build up fast," he said.

Shearer also advised growers to rotate insecticides to avoid the build up of resistance.

And, he said, "I think 20 days before harvest is the most crucial time to protect cherries from this fly."

In laboratory tests, organophosphates outperformed other insecticides, Shearer said.

"Newer pyrethroids" also performed well, "but they are not IPM friendly," he said.

Neonicotinoid insecticides "surprisingly aren't that good" at controlling the fly, Shearer said.