Pest Of The Month: Spotted Wing Drosophila

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Pest Of The Month: Spotted Wing Drosophila

Identification

Due to our mild climate, Florida has traditionally been a haven for imported pests and diseases. This past August, another new pest insect, the spotted wing drosophila (Drosophila suzukii), was found in Hillsborough County where a single male fly was captured in two separate traps located about 3 miles apart. Since then, trapping is underway to delineate the fly’s distribution and population levels.

This pest is of typical size and appearance for a drosophila fruit fly with an adult body length of approximately 2 to 3 millimeters, red eyes, yellowish-brown body color, and dark bands on the abdomen. The males are relatively distinctive, with a small dark spot on the wing near the tip, hence the name “spotted wing.” Florida growers should be on the lookout for the appearance of this pest.

Survival And Spread

In the fall of 2008, the first reports emerged of an unfamiliar fruit pest in the Watsonville area of California when “vinegar fly” (Drosophila) larvae were found in maturing fruits of raspberries and strawberries. This was unusual, as vinegar flies (including the well-known and ubiquitous D. melanogaster) typically lay eggs on damaged and decaying fruit. This pest, new to North America, was determined to be Drosophila suzukii.

For more information on spotted wing drosophila, click here.

Fly populations are now widespread in central California, and detections have been made statewide. High fly counts have been reported again in raspberry fields this summer in California, and flies have been found infesting fresh cherries with severe production losses reported in some areas.

Of particular concern is the high reproductive potential of the fly. Local populations can go through multiple generations and build to very large population sizes in a single cropping cycle. As soon as larvae hatch from the egg, they begin feeding inside the fruit. Within as little as two days, the fruit begins to collapse around the feeding site. Mold and infestation by secondary pests contribute to further damage to fruit.

In mid-season, the adult life span is typically three to nine weeks. However, flies emerging late in the season overwinter and may live many months until the following summer. Adult activity is highest at about 68°F and declines above 86°F. Females may lay seven to 16 eggs per day.

As the fly is reported to thrive at cool temperatures, Florida’s winter and spring berry crops probably are at highest risk. However, the discovery of this fly in the middle of summer casts some doubt on the assessment of the earlier observations on heat tolerance of the pest.

Gene McAvoy is a UF/IFAS Hendry County Extension agent based in LaBelle, FL.

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