National Pest Alert: Spotted Wing Drosophila


July 1, 2019 - USDA and Regional IPM Centers


The Spotted Wing Drosophila (SWD), Drosophila suzukii, is a small vinegar fly that damages many fruit crops. Unlike most other vinegar flies that require damaged fruit to attack, SWD causes damage when the female flies cut a slit and lay eggs in healthy fruit.

This insect is a pest of blueberry, blackberry, raspberry, strawberry, cherries, grapes and tree fruits, with a preference for softer-fleshed fruit. Given its potential to infest fruit, it is important to learn about monitoring and management of SWD to minimize the risk of larvae developing in fruit and affecting fruit marketability.
Spotted Wing Drosophila was first discovered in the western United States in 2008 and is now well-established throughout North America and Europe.


Female SWD can cut into intact fruit using their serrated ovipositor to inject eggs under the skin. Consequently, the larvae of SWD can be present during ripening, and will be in after harvest. Damage to fruit by egg laying and larval feeding can lead to secondary fruit rots as fungal diseases may be introduced, further affecting fruit quality. There is a greater risk of fruit contamination at harvest from SWD compared with native vinegar fly species that lay eggs only in already-damaged and rotting fruit.
The adult SWD lives for about two weeks and can lay more than 300 eggs. This demonstrates their high potential for fruit infestation and distribution through a field if not controlled. Infested fruit do not show obvious symptoms of infestation at first, with only a small pinprick visible from egg-laying. Within a few days, the fruit flesh will start to break down, leading to discolored regions and eventual collapse of the tissues. By this point, the white larvae can be relatively easy to detect.


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