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Spotted Wing Drosophila

 Spotted Wing Drosophila
The photo is by J.Kalisch and M. Rethwisch.

Well, once again we have been "invaded" by a foreign pest. This is not your mother-in-law from out of state, but one of the many pests that have "jumped ship" (or airplane) from another country to become a threat to our food sources. The USDA tries to inspect/quarantine shipments of food and other goods coming into the country and sometimes between states, but often if some adult insects find their way into an open door and survive the plane ride over, they just fly out once the plane has landed.

Many of our insect pests are of foreign origin, going way back (the European corn borer was introduced in the early 1900s) and more recently (the soybean aphid in 2000). Often these insects become well established because their natural enemies don't come along with them. This results in a "tidal wave" of damage as these new pests spread before our native natural enemies discover the new food source and help balance the scales a little bit.

The newest pest arrival is the Spotted Wing Drosophila (SWD), a tiny vinegar fly with the potential to damage many fruit crops. It was first detected in the North Central region of the US in Michigan in 2010, and has spread rapidly. This summer the SWD was captured in nearly every Nebraska county where a trap was set out. Although traps have not been set throughout the entire state of Nebraska, traps have caught this insect in all corners of the state, including Scottsbluff, Lincoln, Dakota, and Gage counties. Because the fly is so small (less than 1/8 inch) and a poor flyer, it is thought that they have spread by human assistance, such as through transport of infected fruit or simply by hitching a ride. 

This fly damages fruit when a female cuts a slit and lays eggs in healthy fruit. It is a pest of most berry crops, cherries, grapes, and other tree fruits, with a preference for fruits with softer flesh. The significance is that there is a greater risk of fruit contamination at harvest compared to native fly species that lay eggs only in already damaged and rotting fruit.

Females lay eggs soon after hatching, and will produce multiple generations during a season in the North Central Region. This means that active monitoring by traps will be required to help manage this insect, along with cultural controls and insecticides in fruit farms.

For more information on the SWD, visit the North Central IPM site.

Image of Keith Jarvi
Keith Jarvi
Extension Educator - Crops & Integrated Pest Management
Keith Jarvi has been with the University of Nebraska since 1979. He received a Master’s Degree in Entomology from North Dakota State University and a Bachelor of Arts degree in Biology from Gustavus Adolphus College in St. Peter, MN. His area of focus is Crops and Integrated Pest Management. As far as insect id he has seen a lot of interesting specimens, but there are always a few surprises every year.

Contact Keith at:
Dixon County Extension
57905 866 Rd
Concord NE 68728-2828
(402) 584-3819