Scientific name: Drosophila suzukii Matsumura
Native range: east Asia
There are no federal, state or local regulations pertaining to spotted wing drosophila as it is so widespread.
Spotted wing drosophila was first found in the U.S. in 2008 where it soon became problematic along the West Coast. After spreading through much of the U.S., the first confirmation of spotted wing drosophila in Minnesota was made in August 2012.
Drosophila species are small brown flies with striped abdomens and red eyes. It takes a close look to differentiate spotted wing drosophila from other flies, but with a little experience and a 10x hand lens anyone can do so. Spotted wing drosophila can only be definitively identified in the adult stage; however, many people have encountered the larvae inside harvested, ripe fruit.
Adult male spotted wing drosophila have a single dark spot near the tip of each wing and two dark combs (may look like bands) on each of the front legs. Adult females do not have these characteristics but can be identified by their large, serrated ovipositors.
Many times fruit does not show obvious symptoms of spotted wing drosophila infestation. There may be only a small pinprick visible from egg-laying. Within a few days, however, the fruit will start to break down and brown discolored and sunken areas will form. By this point, the white larvae can be relatively easy to detect within the fruit. People will commonly not recognize that berries are infested until they are placed together in a container which often results in the larvae moving to the top surface of the berries.
Spotted Wing Drosophila Volunteer Surveyor Info
Many species of flies could be confused for spotted wing drosophila, particularly when trying to identify females. Other drosophila species will be similar but can be differentiated by the lack of wing spots (males) or the small, weakly toothed ovipositors.
Guide to differentiating spotted wing drosophila from other common flies
Host Plants - In Minnesota, raspberry has been the hardest hit crop. Other host crops that occur in Minnesota that are susceptible to spotted wing drosophila attack include blackberries, blueberries, strawberries, grapes, plums and cherries. Spotted wing drosophila will also attack wild berries such as elderberry and buckthorn and these hosts could serve as a reservoir.
Impact - Research in California has shown losses as high as a 40 percent for blueberries (Bolda et al. 2010) and 20 and 50 percent losses in strawberries and raspberries, respectively (Goodhue et al. 2011 ). Minnesota has an estimated 750 acres of raspberries, strawberries, grapes, and blueberries valued at approximately $9.9 million. Another concern is the growing number of high-tunnel operations in Minnesota. There are currently more than 5,000 statewide, valued at approximately $25 million. Spotted wing drosophila has been found to infest crops planted in these structures.
Although not harmful to eat, raspberries, blackberries, and other soft fruit with spotted wing drosophila larvae inside are not marketable for commercial fruit growers.
Bolda M., R. E. Goodhue, & R. G. Zalom. 2010. [SWD]: Potential economic impact of a newly established pest. Giannini Foundation of Agric. Econ., UC 13: 5–8.
Goodhue, R.E., M. Bolda, D. Farnsworth, J.C. Williams, & F.G. Zalom. 2011. [SWD] infestation of California strawberries and raspberries: Economic analysis of potential revenue losses and control costs. Pest Manage. Sci. 67:1396-1402.
2017 updates: Spotted wing drosophila has been captured in Anoka, Dakota, Douglas, Washington and Watonwan Counties so far in 2017. A total of 32 sites in 25 counties are being monitored with traps by volunteers this year.
2016 summary: The MDA was able to recruit 79 volunteers from 36 counties to monitor for SWD in the 2016 field season. This year we confirmed SWD in 34 counties, up from 23 counties in 2015. Confirmations came both from the volunteer monitoring as well as MDA monitoring through the Pathways survey in community gardens. The earliest SWD activity reported was from University of Minnesota research plots in Dakota, Wright, Washington and Rice Counties the week of June 13, 2016. This was approximately 10 days earlier than the first activity found in 2015. Our latest positive confirmations came the week August 8 from two growers in Cass and Roseau Counties.
2015 summary: 63 volunteers from 44 counties participated in the SWD survey during 2015. These volunteers were responsible for confirmation of SWD activity in 13 counties. SWD activity in an additional 3 counties was confirmed through other survey work and 7 counties were confirmed through reports to "Arrest the Pest". SWD activity was reported in an additional 8 counties but could not be confirmed by the MDA. The first confirmation of the summer was made by the University of Minnesota in Dakota and Washington Counties during the week of June 23. Rock County was also reported around this same time. The latest confirmation of the year was during the week of August 19 from Houston County.
Monitoring for spotted wing drosophila is important. Growers can use traps to monitor for adult flies and inspect fruit regularly for the presence of larvae. If spotted wing drosophila is found, management techniques are available to reduce the impacts.
The Minnesota Department of Agriculture and University of Minnesota are coordinating a volunteer network to track the start of spotted wing drosophila activity throughout the state. Updates will be posted here as they come in.
Contact the Minnesota Department of Agriculture via Arrest the Pest if you suspect an infestation of spotted wing drosophila in Minnesota.
Last Updated: June 6, 2017