COUNTY AG NEWS

Spotted Wing Drosophila

Spotted wing drosophila is an invasive vinegar fly native to Southeast Asia. This invasive fly is very similar in size and appearance to the common fruit fly. It was first discovered in the continental United States in California in 2008.

SWD quickly spread throughout the Pacific Northwest and Canada, and was found in Florida in 2009. At least 45 states have now reported SWD, with Michigan and Wisconsin first reporting the insect in 2010. Breeding populations and fruit infestations in Wisconsin were reported in 2012 and were most severe in fall-bearing raspberries. This can be an economically devastating insect for fruit growers.

So far this year SWD flies have been captured in Columbia, Dane, Door, La Crosse, Pierce, Sauk, and Trempealeau counties.

The female SWD has a serrated ovipositor that allows her to cut into healthy fruit to lay eggs. Larvae feed within healthy fruit tissue causing tissue collapse within a few days; consequently crop loss can be severe. SWD adults are small, 1/16 to ⅛ inch long with red eyes and a light brown thorax and abdomen. SWD eggs are tiny and white, and larvae are cream-colored, wormlike, legless, and up to ⅛ inch long.

SWD prefers thin-skinned, soft-fleshed fruit and is primarily a pest of berry crops, including blackberries, raspberries, strawberries, blueberries, and currants. Grapes and tree fruits are also hosts for SWD, as are non-edible fruiting plants such as snowberry, pokeweed, dogwood, honeysuckle, bittersweet nightshade, as well as buckthorn.

Spotted wing drosophila is an invasive vinegar fly native to Southeast Asia. This invasive fly is very similar in size and appearance to the common fruit fly. It was first discovered in the continental United States in California in 2008. SWD quickly spread throughout the Pacific Northwest and Canada, and was found in Florida in 2009. At least 45 states have now reported SWD, with Michigan and Wisconsin first reporting the insect in 2010. Breeding populations and fruit infestations in Wisconsin were reported in 2012 and were most severe in fall-bearing raspberries. This can be an economically devastating insect for fruit growers. So far this year SWD flies have been captured in Columbia, Dane, Door, La Crosse, Pierce, Sauk, and Trempealeau counties. The female SWD has a serrated ovipositor that allows her to cut into healthy fruit to lay eggs. Larvae feed within healthy fruit tissue causing tissue collapse within a few days; consequently crop loss can be severe. SWD adults are small, 1/16 to ⅛ inch long with red eyes and a light brown thorax and abdomen. SWD eggs are tiny and white, and larvae are cream-colored, wormlike, legless, and up to ⅛ inch long. SWD prefers thin-skinned, soft-fleshed fruit and is primarily a pest of berry crops, including blackberries, raspberries, strawberries, blueberries, and currants. Grapes and tree fruits are also hosts for SWD, as are non-edible fruiting plants such as snowberry, pokeweed, dogwood, honeysuckle, bittersweet nightshade, as well as buckthorn.

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