Big problems often come in small packages. Such is the case with spotted wing drosophila (SWD), a new threat to both commercial and home garden fruit plantings, especially berry crops. This minute fruit fly, first found in California 2008, has now spread to many areas of the country, including the Pacific Northwest, the upper Midwest, parts of Canada, and many states in the eastern U.S.
What makes this fruit fly different from the ones we commonly see buzzing around overripe fruits in our kitchens is its ability to infest healthy fruits. The female has an ovipositor shaped like a serrated knife that lets her cut into and lay eggs in sound fruits. The larvae hatch out and feed on the fruit, making it inedible. SWD is primarily a pest of berries, especially raspberries and blackberries, and stone fruits (peach, cherry, nectarine), but it can attack a wide range of fruits. It wreaks its havoc mainly late in the summer, so late season berries are at the most risk.
What can you do to minimize the threat from this tiny pest? Start with excellent garden sanitation. Harvest fruits frequently as soon as they are ripe. Dispose of any culled fruits in plastic bags in the trash or place them in plastic bags to "cook" in the sun to kill any larvae that might be inside. Small berry plantings can be carefully covered with fine (1/32 inch) netting to exclude flies. If your fruit plants become infested, you can use insecticide treatments such as spinosad for control; be sure to read and follow all label instructions and precautions when using any insecticide.
Monitoring for SWD can help you determine if you have a problem and if your treatments are bringing it under control. Make a simple trap from a plastic container baited with yeast or cider vinegar bait and containing a yellow card coated with sticky material to snag entering flies.
To find out more about identifying, monitoring, trapping, and controlling SWD, check out MSU SWD site and Cornell Cooperative Extension Fruit Resources . (Image courtesy of Hannah Burrack, North Carolina State University, Bugwood.org)