Issue 12, July 26, 2013

Spotted Wing Drosophila: A New Pest of Illinois Fruits

In the upcoming weeks as fruit crops ripen and become ready for harvest, the invasive pest Spotted Wing Drosophila (SWD) will begin to make its appearance. Originally from East Asia, SWD first appeared in the Western US in 2008 and became widespread throughout the country within a matter of years. Detected in Illinois in 2012, infestations were confirmed in Pope, Union, Marion, Champaign, Tazewell, Adams, and Ogle Counties, but is likely to be present throughout the state.

Spotted Wing Drosophila is a small vinegar (fruit) fly. Females lay eggs in healthy, ripe fruit using their distinct ovipositor with two rows of dark, serrated teeth that saw open a layer of skin. Larval feeding will cause flesh breakdown, discoloration, and lead to a healthy fruit’s decay. Fungal pathogen may also be introduced. This makes SWD more destructive than native fruit flies that only lay eggs in already rotting and decaying fruit. SWD feed on a large number of host plants including ornamental shrubs and trees, fruits, and vegetables.

Many of the potential host plants are found and grown in Illinois including raspberries, blueberries, apples, pears, blackberries, grapes, tomatoes, strawberries, and more. Also, within a single growing season there can be over 10 generations of SWD. This is due to their extremely short lifespan and rapid reproduction; they live up to 8 days and can produce over 100 eggs in a single day. This can allow for the rapid growth of populations and infestations to occur, so early management and detection are important while prevention is the best management.

Identification between native fruit flies and SWD is very important for they are similar in appearance to many native Drosophila species. SWD adults are small flies about 1/8 inch with red eyes, a brown thorax, and black strips on the abdomen. Male SWD have a distinct black spot on the tip of each wing while females have the distinct ovipositor mentioned above. Larvae are small white maggots that will be seen feeding in fruit.

Key Characteristics of male and female SWD

More information, including how to trap for, and report SWD in Illinois can be found on the Illinois SWD Factsheet.

Other websites with lots of SWD facts:
Michigan State Spotted Wing Drosophila Site
Oregon State Spotted Wing Drosophila Site
Spotted Wing Drosophila in the Northeast

Kelly Estes

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