June 1, 2020 - Matthew J. Grieshop, Diane Brown, Rufus Isaacs, Julianna Wilson,

Pest background

Spotted wing drosophila (SWD), Drosophila suzukii, is a relatively recent and serious pest of wild and cultivated berries (e.g. strawberries, blueberries, raspberries, blackberries) and cherries. It was first detected in California in 2008 and in Michigan in 2010. It is now present throughout much of the world. While SWD is similar in appearance to other vinegar flies, the SWD female possesses a saw-like ovipositor that allows it to lay eggs in ripening as well as rotting fruits. Fruit are susceptible to SWD when they begin to color until they are harvested. Eggs hatch inside the fruit, and the small white larvae feed, eventually causing fruit to collapse. Eggs develop into adults in as little as 8 days and individual females can lay more than 300 eggs, allowing populations to increase rapidly.

Identifying SWD and their damage

Adult SWD are 2-3 mm (5/64-1/8 inch) long, yellow to golden brown in color, with red eyes, and rounded abdomens. Male (but not female) SWD have a distinctive black spot near the tip of each wing, while females have a serrated ovipositor used to deposit eggs into developing fruit (Fig. 1). Larvae are off-white and grow from 0.1 mm when they hatch to 2-3 mm when mature. Larvae develop rapidly and are typically visible within 3 days of hatching. Larval feeding causes rapid break down of fruit tissues (Fig. 2). Mature larvae form a brown pupal case before transforming into adult flies.


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