Spotted wing drosophila (SWD) male

Spotted wing drosophila (SWD), Drosophila suzukii, is an invasive and destructive pest originating from eastern Asia. It is a pest that can not be managed with pesticides alone. Caneberries such as raspberry and blackberry appear to be most affected followed by strawberries and blueberries. Among the tree fruits, cherries seem to suffer heavy damage.

If SWD is found, home gardeners should wash fruits thoroughly. For clean fruits commercial growers should harvest and destroy all ripe and ripening fruits when SWD is found. Follow-up with weekly (sometimes bi-weekly) spraying with organo-phosphate and pyrethroid classes of pesticides. Wet weather conditions and poor sanitation practices after fruit harvest worsen SWD attacks. Hot and dry weather lessens fruit injury.

Good sanitation is as important as pesticide spraying to prevent future infestations. Eliminate all fruits that have fallen to the ground and all infested fruits remaining on the plants to reduce SWD populations that might infest later ripening fruits or next year’s crop.

SWD can develop large populations, 10-12 generations per growing season in the mid-Atlantic and Southern Appalachian regions (USDA hardiness zones 5-8). It overwinters as adults and is active in early spring. They are most active when highs are between 62° to 83ºF, humid conditions, and fruits are present. The SWD can complete one generation in a short 12 to 14 days.

The adult SWD looks like many other Drosophila species, including the common vinegar flies that infest rotting fruit. SWD attacks the fruits in all stages- undamaged, ripe or unripe. SWD adults are small flies (size: 1/10 inch) with red eyes and a pale brown body with black stripes on their abdomen. Adult males have a distinctive black spot near the tip of each wing. Females do not have these spots. The immatures of the SWD are very small white maggots.

Special Thanks to: Dr. Frank Hale, Extension Entomologist, University of Tennessee, Nashville, TN