Spotted wing drosophila
The spotted wing drosophila (Drosophila suzukii) is a small invasive fly that looks very similar to our usual fruit fly (sometimes called vinegar fly) but it acts very differently. The spotted wing drosophila will attack undamaged fruit. It is especially damaging to thin skinned fruit like raspberries, blackberries, blueberries, cherries, strawberries, grapes, etc. It attacks right as fruit are ready for harvest so control measures with insecticides are limited.
Spotted wing drosophila, native to Asia, was found in the mainland U.S. (California) in 2008, by 2009 it was found in Oregon, Washington and Florida. By 2010 it had spread to several other states including Michigan. In 2011, Wisconsin confirmed SWD and in 2012 Illinois and Minnesota confirmed SWD. It appears that SWD is here to stay and has spread very quickly. In Iowa we have collected adult flies in a trap in Story County.
Spotted wing drosophila can be distinguished from the normal fruit fly (Drosophila melanogaster) but the presence of spots on the wings of the male and a serrated edge on the ovipositor (egg layer) of the female. It is the serrated, saw-like, edge on the female’s ovipositor that allows this species to attack pre-harvest healthy fruit.
Sanitation is necessary for management of SWD. Picking all fruit when harvesting and remove and destroy any fallen, damaged and overripe fruit. There are insecticides available but options will be limited. At this point there is no need for treatment until SWD has been confirmed in your area.