Drosophila suzukii

Drosophila suzukii
A male D. suzukii. Note the dark spots near the tips of the wings.
Photo by M. Francisco
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Drosophilidae
Genus: Drosophila
Subgenus: Sophophora
Species group: D. melanogaster species group
Species subgroup: D. suzukii species subgroup
Species: D. suzukii
Binomial name
Drosophila suzukii
(Matsumura, 1931)

Drosophila suzukii, commonly called the spotted-wing drosophila, is a vinegar fly—closely related to Drosophila melanogaster (the common vinegar fly). D. suzuki, 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.[1]

Native to southeast Asia, D. suzukii was first described in 1931 by Matsumura. Observed in Japan as early as 1916 by T. Kanzawa,[2] D. suzukii was widely observed throughout parts of Japan, Korea, and China by the early 1930s.[2] 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[3] and is now widespread throughout California's coastal counties,[4] western Oregon, western Washington,[3] and parts of British Columbia[5] and Florida.[6] During the summer of 2010 the fly was discovered for the first time in South Carolina, North Carolina,[7] Louisiana,[8] and Utah.[9] In Fall 2010 the fly was also discovered in Michigan[10] and Wisconsin.[11] The pest has also been found in Europe, including the countries of Belgium, Italy, France, and Spain.[12][13]

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.[3] Research investigating the specific threat D. suzukii poses to these fruit is ongoing.[14]

Description

Like other members of the vinegar fly family, D. suzukii is small, approximately 2 to 3.5 mm in length and 5 to 6.5 mm in wingspan [2] 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 3.5 mm in length.[3]

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.[15] The cherry fruit fly is significantly larger than D. suzukii (up to 5 mm) 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.

Lifecycle

The lifespan of D. suzukii varies greatly between generations; from a few weeks to ten months.[2] Generations hatched early in the year have shorter lifespans than generations hatched after September.[2] 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.).[3] 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.

Adults emerge from overwintering when temperatures reach approximately 10 °C (268 degree days).[3] The fertilized female searches for ripe fruit, lands on the fruit, inserts its serrated ovipositor to pierce the skin and deposits a clutch of 1 to 3 eggs per insertion. Females will oviposit on many fruits and in regions of scarce fruit, many females will oviposit on the same fruit. In captivity in Japan, research shows up to 13 generations of D. suzukii may hatch per season. A female may lay as many as 300 eggs during its lifespan. With as many as 13 generations per season, and the ability for the female to lay up to 300 eggs each, the potential population size of D. suzukii is huge. It is also important to note that males of D. suzukii become sterile at 30 °C and population size may be limited in regions that reach that temperature.

The larvae grow inside the fruit. The oviposition site is visible in many fruit by a small pore scar in the skin of the fruit often called a "sting". After 1 or 2 days, the area around the "sting" softens and depresses creating an increasingly visible blemish.[3] The depressions may also exude fluid which may attract infection by secondary bacterial and fungal pathogens.[4] Larvae may leave the fruit, or remain inside it, to pupate.

Economic Impact

The economic impact of D. suzukii on fruit crops is negative and significantly affects a wide variety of summer fruit in the United States including cherries, blueberries, grapes, nectarines, pears, plums, pluots, peaches, raspberries, and strawberries. Damage was first noticed in North America in the western states of California, Oregon, and Washington in 2008; yield loss estimates from that year vary widely, with negligible loss in some areas to 80% loss in others depending on location and crop.[4] The $500 million actual loss due to pest damage in 2008—the first year D. suzukii was observed in California—is an indication of the potential damage the pest can cause upon introduction to a new location. Economic losses have now been reported across North America and in Europe as the fly has spread to new areas. Future losses may decrease as growers learn how better to control the pest, or may increase as the fly continues to spread.

References

  1. ↑ Walsh et al. Drosophila suzukii (Diptera: Drosophilidae): Invasive Pest of Ripening Soft Fruit Expanding its Geographic Range and Damage Potential J. Int. Pest Man. 2:G1-G7
  2. 1 2 3 4 5 Kanzawa, T. 1939 Report. Translated from Japanese by Shinji Kawaii
  3. 1 2 3 4 5 6 7 Walsh, D. Press Release, Washington State University. 2009
  4. 1 2 3 Bolda, M, Goodhue, R, Zalom. Spotted Wing Drosophila: Potential Economic Impact of Newly Established Pest. Giannini Foundation of Agricultural Economics, University of California. 2009.http://giannini.ucop.edu/media/are-update/files/articles/v13n3_2.pdf
  5. ↑ Spotted Wing Drosophila (Fruit Fly) Pest Alert. British Columbia Ministry of Agriculture and Lands. December 2009. http://www.agf.gov.bc.ca/cropprot/swd.htm
  6. ↑ Steck, G, Dixon, W, Dean, D. Pest Alert, Spotted Wing Drosophila, a fruit pest new to North America. 2009
  7. ↑ Spotted Wing Drosophila. NC Small Fruit, Specialty Crop, and Tobacco IPM. 2010. http://ncsmallfruitsipm.blogspot.com/p/spotted-wing-drosophila.html
  8. ↑ Spotted Wing Drosophila. Louisiana Department of Agriculture and Horticulture. August 2010. http://www.ldaf.state.la.us/portal/Portals/0/AES/Horticulture/Quarantine_programs/Spotted%20Wing%20Drosophila%20Profile.pdf
  9. ↑ Davis, R., Alston, D., Vorel, C. Spotted Wing Drosophila September 2010. http://extension.usu.edu/files/publications/publication/ENT-140-10.pdf
  10. ↑ Early detection program finds a new invasive pest of fruit in Michigan MSU Fruit Crop Advisory Team Alert, 29 Oct 2010. http://www.ipmnews.msu.edu/fruit/Fruit/tabid/123/articleType/ArticleView/articleId/3202/Early-detection-program-finds-a-new-invasive-pest-of-fruit-in-Michigan.aspx
  11. ↑ Hamilton, K. Wisconsin Pest Bulletin. 19 November 2010. https://onlineservices.datcp.wi.gov/pb/pests.jsp?categoryid=32&issueid=155
  12. ↑ Belgian Journal of Zoology - Drosophila suzukii (Diptera: Drosophilidae): A pest species new to Belgium. - Link
  13. ↑ Drosophila suzukii (Diptera: Drosophilidae): Spotted wing drosophila. European and Mediterranean Plant Protection Organization. January 2010. http://www.eppo.org/QUARANTINE/Alert_List/insects/drosophila_suzukii.htm
  14. ↑ Herring, P. Grant funds help regional effort to combat spotted wing drosophila. 29 April 2010. http://extension.oregonstate.edu/news/story.php?S_No=729&storyType=news.
  15. ↑ Spotted Wing Drosophila, Drosophila suzukii: A New Pest in California. UC IPM Online, 10 Apr 2010. http://www.ipm.ucdavis.edu/EXOTIC/drosophila.html

External links

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Further reading

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