Spotted Wing Drosophila Found In Minnesota
August 21, 2012 
The Minnesota Department of Agriculture and the University of Minnesota are making the state’s growers and homeowners aware of the presence of a new pest. The spotted wing drosophila (SWD) feeds on small fruits and stone fruits. The SWD is an invasive pest of Asian origin that was first detected in the continental U.S. in California in 2008 and has since spread to several western and eastern states.
The first two detections of this pest in Minnesota were made by members of the public who reported the flies to the Minnesota Department of Agriculture (MDA). First, a homeowner from Hennepin County contacted the MDA about some flies she found in a yeast-baited trap she placed near a raspberry patch. Days later, the MDA was contacted by a citizen who found an abundance of maggots in some wild raspberries picked in Ramsey County. The MDA quickly followed up on both of these reports to visit the sites, collect specimens and confirm the identity of this new pest.
The SWD feeds on healthy, intact, ripening fruits. In particular, the SWD will feed on thin-skinned, soft fruits such as raspberries, blackberries, blueberries, strawberries, grapes, plums, and cherries.
The SWD is difficult to distinguish from other species of small flies. The SWD is a small fly, with yellowish-brown coloration and prominent red eyes. Male SWD have dark spots near the tips of the clear wings. Several other species of small flies with spots on their wings can easily be confused for SWD. Female SWD have few distinguishing characters and are even more difficult to identify. Larvae of SWD are white with a cylindrical body that tapers on both ends. To date, SWD is known to be an outdoor pest; fruit flies found indoors are likely to be a different species.
With this pest being so new to Minnesota and the U.S., little is known about how big of an impact it will have and what management tactics will be most effective. The MDA will be working with the University of Minnesota (Extension and the Department of Entomology) to determine how widespread this pest is in Minnesota and to alert farmers and gardeners of its presence and potential impacts. The University of Minnesota will also be developing recommendations for management of this pest on Minnesota fruit crops. SWD could be particularly devastating to blueberry, raspberry, and grape growers, but more information is needed on when the pest is active in Minnesota and how well it can survive the state’s winter weather.
For more information, go to http://blog.lib.umn.edu/efans/ygnews/2012/08/minnesotas-newest-fruit-pest-t.html.
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