Drosophila suzukii, commonly called the spotted wing drosophila or SWD, is a fruit fly. D. suzukii, originally from southeast Asia, is becoming a major pest species in America and Europe, because it infests fruit early during the ripening stage, in contrast with other Drosophila species that infest only rotting fruit.
Native to east Asia, D. suzukii was first described in 1931 by Shōnen Matsumura, it was observed in Japan as early as 1916 by T. Kanzawa.
D. suzukii is a fruit crop pest and is a serious economic threat to soft summer fruit; i.e., cherries, blueberries, raspberries, blackberries, peaches, nectarines, apricots, grapes, and others. Research investigating the specific threat D. suzukii poses to these fruit is ongoing.
Description
Like other members of the Drosophilidae, D. suzukii is small, approximately in length and in wingspan and looks like its fruit and vinegar fly relatives. Its body is yellow to brown with darker bands on the abdomen and it has red eyes. The male has a distinct dark spot near the tip of each wing; females do not have the spotted wing. The foreleg of the male sports dark bands on the first and second tarsi. The female has a long, sharp, serrated ovipositor. The larvae are small, white, and cylindrical reaching in length.
When first observed in a new region, D. suzukii has often been confused with the western cherry fruit fly (Rhagoletis indifferens) and was given the short-lasting name cherry vinegar fly. The cherry fruit fly is significantly larger than D. suzukii (up to ) and has a pattern of dark bands on its wings instead of the telltale spot of D. suzukii. The telltale spots on the wings of male D. suzukii have earned it the common name "spotted wing drosophila" (SWD).
Unlike its vinegar fly relatives which are primarily attracted to rotting or fermented fruit, female D. suzukii attack fresh, ripe fruit by using their saw-like ovipositor to lay eggs under the fruit's soft skin. The larvae hatch and grow in the fruit, destroying the fruit's commercial value. Economic impacts are significant; losses from large scale infestation (20% loss) across the US alone could equate to farm gate impacts > $500M.
D. suzukii has a slow rate of evolution due to its lower number of generations per year, because it enters winter diapause.
Distribution
Native to southeast Asia, D. suzukii was first described in 1931 by Matsumura. Observed in Japan as early as 1916 by T. Kanzawa, it was widely observed throughout parts of Japan, Korea, and China by the early 1930s. By the 1980s, the "fruit fly" with the spotted wings was seen in Hawaii. It first appeared in North America in central California in August 2008, then was found in Oregon and Washington State by Lee et al., 2011 in the Pacific Northwest in 2009, and is now widespread throughout California's coastal counties, western Oregon, western Washington, and parts of British Columbia and Florida. During the summer of 2010 the fly was discovered for the first time in South Carolina, North Carolina, Louisiana, and Utah. In Fall 2010 the fly was also discovered in Michigan and Wisconsin. The fly was first discovered in the northeastern states in 2011 and in Minnesota and Idaho in 2012. As D. suzukii continues to spread, most of the states will most likely observe it. The pest has also been found in Europe, including the countries of Belgium, Italy, France, and Spain.
Lifecycle
The lifespan of D. suzukii varies greatly between generations; from a few weeks to ten months. Generations hatched early in the year have shorter lifespans than generations hatched after September. Research shows that many of the males and most of the females of the late-hatching generations overwinter in captivity—some living as long as 300 days. Only adults overwinter successfully in the research conducted thus far. In Washington state, D. suzukii has been observed in association with two exotic and well-established species of blackberry, Rubus armeniacus (= Rubus discolor) and Rubus laciniatus (the Himalayan and Evergreen Blackberries, respectively.). The fly has been observed reproducing on many other species of soft-skinned wild fruit, however, research is still ongoing to determine the quality of individual species as reproductive hosts.