Workshop Teaches Growers to Identify Spotted Wing Drosophila

Salt test for spotted wing drosophila shows larvae floating out of fruit. Photo: Ohio State University.

COLUMBUS, Ohio – In order to combat the damaging impact of spotted wing drosophila on small fruit crops, growers have to know what the winged pests look like so they can start treatment even after finding just one of them in their fields, according to an entomologist with the College of Food, Agricultural, and Environmental Sciences at The Ohio State University.

The spotted wing drosophila, which can destroy an entire fruit crop, looks like a common vinegar fly to the untrained eye, said Jim Jasinski, an Ohio State University Extension educator and Integrated Pest Management program coordinator.

If even one of these pests is detected in a field with ripening fruit, it needs to be treated, he said.

“When spotted wing drosophila comes into a field, it will attack ripening or ripe fruit,” Jasinski said. “For this pest, the threshold to begin management is one fly, period.

“Traditional growers have got to enact the management program of spraying a weekly insecticide through the end of harvest. They should monitor when the insect comes onto their farm and prevent females laying eggs in the fruit, which eventually turn into maggots and begin to tunnel into the fruit.”

To help growers learn how to identify spotted wing drosophila, Jasinski and Celeste Welty, an OSU Extension entomologist, will hold a 90-minute workshop on identifying these insects from other insects caught in monitoring traps. The workshop is from 1-2:30 p.m. May 20 in Room 130, Research Services Building, 1680 Madison Ave., on the campus of the Ohio Agricultural Research and Development Center in Wooster.

OSU Extension and OARDC are the outreach and research arms, respectively, of the college.

"During the workshop, participants will use a stereo microscope to see the tiny characteristics that separate these flies from other flies and beetles caught in the traps,” Jasinski said.

The adult male spotted wing drosophila is distinguished from other fruit flies by spots on its wings that can be visible with the naked eye, but there are also two dark bands on its front legs that need to be seen to positively confirm the pest.

The adult female spotted wing drosophila is distinguished from other fruit flies because of its large, saw-like, hard ovipositor, which can best be seen using a stereo microscope, Jasinski said.

“One of our goals is for the participants to be able to separate male and female spotted wing drosophila flies from other insects caught in the baited traps,” he said. “We want to help participants to understand how small spotted wing drosophila are, and learn the key characteristics of the males and females to be able to select them out of all of the other insects that are collected in the traps if they have access to the proper equipment.”

By the end of the workshop, growers should have gained the confidence to know how to identify spotted wing drosophila, and then to start their management plan, Jasinski said.

Spotted wing drosophila is a vinegar fly that targets small fruit crops, including cherries, raspberries, blackberries, blueberries, grapes, peaches, plums and sometimes strawberries. The pest causes damage through larval feeding on ripening fruit. Damage starts as a tiny scar on the skin of the fruit, with the skin collapsing in two or three days and mold developing.

The pest has caused significant losses for fruit growers in several states, including Michigan, where many blueberry, bramble and strawberry growers reported up to 50 percent fruit loss in 2012, according to a report from Michigan State University Extension.

The workshop is free but registration is required as the room holds space for only 18 participants. Registration can be found at

Tracy Turner
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Jim Jasinski