Spotted Wing Drosophila

Scientific name: Drosophila suzukii Matsumura

Native range: East Asia

At Risk

In Minnesota, raspberry has been the hardest hit crop. Other host crops that occur in Minnesota that are susceptible to spotted wing drosophila (SWD) attack include blackberries, blueberries, strawberries, grapes, plums and cherries. SWD will also attack wild berries such as elderberry and buckthorn and these hosts could serve as a reservoir.

Research in California has shown losses as high as a 40 percent for blueberries (Bolda et al. 2010) and 20 and 50 percent losses in strawberries and raspberries, respectively (Goodhue et al. 2011). Minnesota has an estimated 750 acres of raspberries, strawberries, grapes, and blueberries valued at approximately $9.9 million. Another concern is the growing number of high-tunnel operations in Minnesota. There are currently more than 5,000 statewide, valued at approximately $25 million. Spotted wing drosophila has been found to infest crops planted in these structures.

Although not harmful to eat, raspberries, blackberries, and other soft fruit with spotted wing drosophila larvae inside are not marketable for commercial fruit growers.

Distribution

Spotted wing drosophila was first found in the U.S. in 2008 where it soon became problematic along the West Coast. After spreading through much of the U.S., the first confirmation of spotted wing drosophila in Minnesota was made in August 2012. Since that time, spotted wing drosophila has been confirmed in the majority of Minnesota counties.

Identification

Drosophila species are small brown flies with striped abdomens and red eyes. It takes a close look to differentiate spotted wing drosophila from other flies, but with a little experience and a 10x hand lens anyone can do so. Spotted wing drosophila can only be definitively identified in the adult stage; however, many people have encountered the larvae inside harvested, ripe fruit.

Adult male spotted wing drosophila have a single dark spot near the tip of each wing and two dark combs (may look like bands) on each of the front legs. Adult females do not have these characteristics but can be identified by their large, serrated ovipositors.

Many times fruit does not show obvious symptoms of spotted wing drosophila infestation. There may be only a small pinprick visible from egg-laying. Within a few days, however, the fruit will start to break down and brown discolored and sunken areas will form. By this point, the white larvae can be relatively easy to detect within the fruit. People will commonly not recognize that berries are infested until they are placed together in a container which often results in the larvae moving to the top surface of the berries.

Look-Alikes

Many species of flies could be confused for spotted wing drosophila, particularly when trying to identify females. Other drosophila species will be similar, but can be differentiated by the lack of wing spots (males) or the small, weakly toothed ovipositors.

Regulatory Status: Non-regulated

There are no federal, state or local regulations pertaining to spotted wing drosophila as it is so widespread.

The SWD monitoring network Counties are all positive for SWD as of last week, August 28, 2015. A lot of SWD are being caught in traps in research sites now with population numbers expected to climb into the thousands before frost knocks them back and forces them into winter diapause.

All sites in NY’s SWD monitoring network reported SWD by the end of August. Counties in white did not have traps reporting to the network.

Reports are coming in of severely infested fall raspberries. This fall will be especially challenging for fall harvest of susceptible fruits. Blackberries and raspberries are particularly vulnerable and will require intensive management with sanitation and insecticide protection. One sanitation strategy used in California for berries is for workers to crush any fruit that has fallen to the ground, reducing the chance of larvae surviving to grow into egg-laying adults. For insecticides, maintaining good coverage is essential, so keep track of rain events that can wash off insecticide (>0.5 inch) and reapply at the appropriate interval listed on the labels.

Late-season blueberries, peaches, plums and grapes are vulnerable to infestation, though not as susceptible as brambles, it will be wise to examine the crop for infestation. Fruit that is softer than it should be, with dull sunken areas and tiny drops of sap may be infested. Hold marketable fruit samples on white paper towels for a day or so and rotate it to see if it is leaking from tiny pinholes indicative of larval breathing sites. Use salt floatation to float out larvae and assess the relative abundance of larval infestation and severity of the problem. Place 50 ripe, marketable fruit in a plastic bag, cover with salt solution (1 Tbsp salt/cup water) and examine in 15-30 minutes for emerging larvae. Larvae are small 1-3 mm or 1/16-2/16 inch long. More on checking fruit for infestation is in the blog Do my fruit have SWD?

Infestations can contribute to sour rot in grapes and fruit decays in other fruit crops. Severely infested raspberries will appear to melt off the plants.

If fruit is still ripening and ripe fruit is infested, clean pick all ripe and overripe fruit and discard it to remove the developing SWD population from the planting. After clean picking and sanitation, apply an effective insecticide to protect the ripening fruit.

Discard infested fruit in clear plastic bags held in the sun to solarize and kill larvae or freeze it. Holding culled fruit in tightly closed plastic bags will prevent SWD adults to emerge from the infested fruit into the environment.

High temperature will dissuade SWD, but hot days this past week in NY have been followed by cool nights which has likely allowed SWD adults to escape the impact of the heat. High humidity is conducive to SWD development, so that factor will also weigh in to make management difficult this fall. The microclimate in the fruit planting can be altered with pruning practices, so plan now to prune for a more open plant canopy in 2016.

Consult the resources in the right hand side bar for more information on SWD.

Spotted wing Drosophila: A serious pest for the home gardener

Since the spotted wing Drosophila (SWD), Drosophila suzukii, was first found in Michigan in 2010, it has become a serious pest of commercially-grown raspberries, blueberries, cherries and other fruit crops, resulting in the loss of well over 25 million dollars. This insect can also be a troublesome pest in home fruit plantings, especially for people who wish to keep pesticide use to minimal levels.

The adult SWD is a small fly, 2-3 millimeters long; the body is usually colored in shades of brown, and its large, compound eyes are red. Adult females can insert eggs through the skin of healthy, intact fruits.

The next stage of SWD is a legless, elongated maggot that feeds internally on the flesh of fruits, causing it to rapidly decay and lose fruit quality. More information about identifying SWD and the damage it makes can be found in Michigan State University Extension’s two-page publication, “Spotted Wing Drosophila Management in Home Fruit Plantings.”

Spotted wing Drosophila are small fruit flies, 2-3 millimeters long. Photo by MSU AgBioResearch.

SWD populations are low in spring but climb rapidly in summer and fall. For this reason, SWD problems tend to be worse on fruits that ripen later in the growing season. For example, summer-bearing raspberries suffer much less damage than fall-bearing raspberries.

The adults and maggots appear similar to a native insect often called the common fruit fly or the vinegar fly, which is technically named Drosophila melanogaster. The common fruit fly is only a nuisance, as it typically does not infest and destroy healthy fruits; it is primarily attracted to over-ripe fruit or fruit damaged by some other pest or during handling. The adult female of the common fruit fly is not able to insert eggs through the skin of intact fruits.

When SWD was first detected in the United States in 2008, it was only known to infest a small number of fruit crops including brambles, such as raspberries and blackberries; sweet and tart cherries; and pears. Since that time, many more host plants have been discovered, and the current tally is over 60 plant species from 24 different plant families. Many of the known hosts are common in home gardens and landscapes. Some are surprising, such as asparagus and burning bush, where SWD can infest the tiny berries the plants produce in summer.

SWD is difficult to control in the yard and garden. It has a high reproductive rate, a short generation time and is not easily detected; people usually find out they have it way too late to take effective actions against it. Good management of SWD problems requires aggressive, pro-active strategies, attention to detail and perseverance. SWD may become the deciding factor for whether or not you continue to grow fruiting trees and shrubs in the home garden.

SWD management for the gardener

  • Select species or varieties that ripen in spring to early summer, before SWD populations build up.
  • Choose a planting location and design that will allow for efficient maintenance, spraying and harvest. SWD will be very hard to manage if you cannot visit the site frequently. Plants need to be spaced and maintained to allow for good penetration of sprays into the canopy. The fruiting zone of plants needs to be readily accessible to assure clean harvests.
  • Carefully consider what other fruiting plants you have on your property and their relative susceptibility to SWD. If possible, remove alternate host plants or take actions to protect them from infestation, too. It may be necessary to seek the cooperation of your neighbors in this process, as adults of SWD can easily fly from one property to another.
  • Use traps to detect the activity of adult SWD and identify when to make pesticide applications. See “Spotted Wing Drosophila Management in Home Fruit Plantings” for information about trapping and pesticide options.

Example of a trap used to attract and capture spotted wing Drosophila adults. Photo by Rufus Isaacs, MSU.

  • Select and apply pesticides carefully. Check product labels to be sure they are registered for use on your crops, the allowable rates and frequency of use, and for the pre-harvest interval (PHI), which is the days or hours you must wait after a spray before eating the fruit. Sprays need to be applied thoroughly, making sure the product is well distributed in the plant canopy.
  • Consider using exclusion netting. If convenient to use in your planting, netting with 1-millimeter (0.03125 inch) mesh can be employed to help protect fruits from SWD. To be effective, the netting must completely cover the plants and be sealed to the surface of the ground. Since the netting would have to be lifted or removed for each harvest, some spraying for SWD might still be necessary.
  • Prompt and clean harvest of ripe fruits is essential. Harvest a few fruits very frequently (daily if possible, but always waiting for pesticide PHIs to expire) rather than wait for many fruits to be ripe at once. Undesirable fruits (small, disfigured or injured, etc.) should not be left on the plants or dropped to the ground, as these can be readily infested by SWD and lead to a serious population increase. Culled fruit should be destroyed in a manner that prohibits SWD from infesting it. Seal culled fruit tightly in a plastic bag and throw it in the trash. Do not bury or compost fruit.
  • When you finish harvesting fruit for the season, SWD will continue to infest any additional fruit that ripens. This may lead to a high pest population that could invade later crops or provide for a greater over-wintering SWD population that may trouble your crops in the following year.

Download tip sheet version of this article: Spotted wing Drosophila: A serious pest for the home gardener

SWD host plant list

  • Adoxaceae: viburnum, blue elderberry, black elderberry, Rocky Mountain elderberry
  • Annonaceae: pawpaw
  • Aquifoliaceae: catberry
  • Araliaceae: devil’s walkingstick
  • Berberidaceae: mayaple, hollyleaved barberry
  • Buxaceae: sweet box
  • Caprifoliaceae: Japanese honeysuckle, Morrow’s honeysuckle, Bell’s blue honeysuckle, tartartian honeysuckle, common snowberry
  • Celastraceae: burning bush
  • Cornaceae: kousa dogwood, silky dogwood, gray dogwood, stiff dogwood, red osier dogwood
  • Cucurbitaceae: cantaloupe, muskmelon
  • Ebenaceae: common persimmon
  • Elaeagnaceae: autumn olive
  • Ericaceae: black huckleberry, blue huckleberry, highbush blueberry, Blue Ridge blueberry
  • Grossulariaceae: golden currant, northern black currant
  • Lauraceae: spicebush
  • Liliaceae: garden asparagus
  • Moraceae: edible fig, Illinois ever bearing mulberry, black mulberry, red mulberry
  • Phytolaccaceae: American pokeweed
  • Ranunculaceae: red baneberry
  • Rhamnaceae: glossy buckthorn, common buckthorn, cascara buckthorn
  • Rosaceae: purple chokeberry, beach plum, wild black cherry, chokecherry, cultivated sweet and tart cherries, peaches, Alleghany blackberry, Himalaya blackberry, northern dewberry, bristly dewberry, black raspberry, red raspberry, purple flowering raspberry, wine raspberry, salmonberry, milkflower cotoneaster, cherry laurel, Portugal laurel, saskatoon berry, strawberry
  • Rutaceae: orange jasmine
  • Solanaceae: tomatoes, climbing nightshade, bittersweet nightshade
  • Taxaceae: Japanese yew
  • Vitaceae: amur peppervine, fox grape, riverbank grape, some varieties of wine grapes

Host plant listings obtained from:

  • Spotted wing drosophila (SWD)- crops of concern and wild hosts by Cornell University
  • Noncrop host plants of spotted wing drosophila in North America by Oregon State University Extension Service
  • Wild hosts of spotted wing drosophila by Ontario Ministry of Agriculture, Food and Rural Affairs
  • Spotted wing drosophila by Pennsylvania State University Extension

Download tip sheet version of the SWD host plant list: Spotted wing Drosophila host plant list

Cornell Fruit Resources

  • Strawberry Substrate Workshop, February 11-13, 2020
    An in-depth strawberry substrate workshop will be held February 11–13, 2020 at the Moakley House, Ithaca, NY Growing strawberries in substrate (soil-less media) can help prevent soil-borne diseases. It can also increase yields, improve quality, and reduce the costs associated with pesticides, fertilizer, and water. In this 3-day workshop, led by Dennis Wilson of Delphy, a worldwide …continue reading “Strawberry Substrate Workshop, February 11-13, 2020”
  • What does SWD do in the winter?
    The Sustainable SWD Management Project’s November 5 webinar covered the seasonal biology and movement of SWD, “SWD in Space and Time: What do we know about the seasonal biology and movement of SWD?” The recording from the webinar is now available on the project’s website. Access the recording here: https://swdmanagement.org/2019/11/webinar-swd-in-space-time/ You’ll gain information on: how …continue reading “What does SWD do in the winter?”
  • Cull fruit and SWD
    Fruit that has dropped to the ground in orchards and berry plantings provides resources for SWD — food and reproduction. Populations of SWD are climbing. SWD made up almost half of the fruit flies caught in traps in an unsprayed research site where ~300 were caught in four traps. I’ve seen lots of fruit flies …continue reading “Cull fruit and SWD”
  • Spotted Lanternfly IPM Conference
    Spotted Lanternfly — On the Doorstep Or Already In Our Fields? Learn more at the 2019 IPM Conference hosted by the New York State Integrated Pest Management Program on August 15, 2019 at the Broome County CCE Farmers Market, 840 Upper Front St., Binghamton, NY. Yes! That’s this Thursday, 8:30 to 4:30. Lunch provided. Earn recertification …continue reading “Spotted Lanternfly IPM Conference”
  • Managing SWD in blueberries
    Blueberries are highly susceptible to SWD. Although early maturing varieties can escape infestation in some years, that hasn’t been the case this year in many areas of NY State. U-Pick and farm stand customers want the best from farm-fresh blueberries and SWD can mar that experience — so be proactive — make sure your customers …continue reading “Managing SWD in blueberries”
  • Sustained catch in Dutchess, Erie, Herkimer, Livingston, Onondaga, Orleans, & Tioga Counties
    Sustained SWD catch was obtained over the last couple of weeks in several counties — Dutchess 1 SWD, Herkimer 6 SWD, Livingston 18 SWD, Onondaga 16 SWD, Orleans at two farms 11 and 9 SWD, and Tioga 1 SWD. Last month, I missed reporting sustained catch in Erie County on June 6, 1 female SWD. …continue reading “Sustained catch in Dutchess, Erie, Herkimer, Livingston, Onondaga, Orleans, & Tioga Counties”
  • High numbers of SWD last week!
    The ability for the SWD population to explode as summer rolls on was demonstrated last week in several counties where I have research projects. Per trap, 5 to 125 SWD were caught in raspberry, blueberry, and tart cherry in mid-July. The totals for the two to four traps set in the orchards and fields were …continue reading “High numbers of SWD last week!”

Drosophila suzukii adults are small (3–4 mm) yellowish-brown flies with red eyes. The adults have a pale brown or yellowish-brown thorax with black bands on the abdomen. The antennae are short and stubby with branched arista. Males have a distinguishing dark spot along the front edge of each wing. Spotless males are also possible, but are rarely observed in the field and should be verified by a taxonomist for positive identification. In addition, males have two rows of combs on each fore tarsus which are absent in females.

Figure 2. Adult female spotted-wing drosophila, Drosophilia suzukii (Matsumura). Photograph by Martin Hauser, California Department of Food and Agriculture.

Figure 3. Head of an adult spotted-wing drosophila, Drosophilia suzukii (Matsumura), frontal view. Photograph by Martin Hauser, California Department of Food and Agriculture.

Figure 4. Wing of an adult male spotted-wing drosophila, Drosophilia suzukii (Matsumura). Spotless males are also possible, but are rarely observed in the field. Photograph by Martin Hauser, California Department of Food and Agriculture.

The females have a serrated ovipositor with which they penetrate the fruit skin. The serrations are much darker than the rest of ovipositor (Kanzawa 1939, Walsh et al. 2011).

Figure 5. Ovipositor of an adult female spotted-wing drosophila, Drosophilia suzukii (Matsumura), lateral view. Photograph by Martin Hauser, California Department of Food and Agriculture.

Figure 6. SEM of an ovipositor of an adult female spotted-wing drosophila, Drosophilia suzukii (Matsumura), lateral view. Photograph by Martin Hauser, California Department of Food and Agriculture.

Figure 7. SEM of an ovipositor of an adult female spotted-wing drosophila, Drosophilia suzukii (Matsumura), posterior view. Photograph by Martin Hauser, California Department of Food and Agriculture.

Figure 8. SEM of genitalia of an adult male spotted-wing drosophila, Drosophilia suzukii (Matsumura). Photograph by Martin Hauser, California Department of Food and Agriculture.

Eggs: The eggs are translucent, milky-white, and glossy. The eggs develop and hatch within the fruit in which they are laid (Walsh et al. 2011).

Larvae: The larvae are milky-white and cylindrical with black mouthparts. The body is tapered anteriorly with elevated posterior spiracles. First instar larvae are approximately 0.07 mm in length. Internal organs of larvae are visible after it has consumed some fruit. Larval development occurs inside the fruit and develops through three instars before pupation. Mature larvae may grow up to 6 mm in length (Kanzawa 1939, Walsh et al. 2011).

Figure 9. Larvae of Drosophila spp. on overripe banana. Photograph by Whitney Cranshaw, Colorado State University, Bugwood.org.

Pupae: The pupae are cylindrical, reddish brown with two small projections at the end. They are approximately 2–3 mm long. Pupation can occur either inside or on the exterior of fruit.

Figure 10. Pupae of Drosophila spp. on overripe banana. Photograph by Whitney Cranshaw, Colorado State University, Bugwood.org.

Life Cycle (Back to Top)

Drosophila suzukii prefers a moderate climate but can also survive in cold conditions (Kanzawa 1939). The flies are most active at 20°C (68°F). Activity becomes reduced at temperatures above 30°C (86°F) or below freezing. However, Drosophila suzukii is firmly established on the island of Hokkaido in Japan where winters average -4 to -12°C (Kimura 2004), suggesting the possibility of its establishment in cooler climates. Preliminary research from Oregon suggests that Drosophila suzukii larvae, pupae, and adults have the potential to survive fluctuating overwintering conditions for periods up to 60 days. Adults are able to withstand longer periods of cold conditions than larvae or pupae (Walsh et al. 2011). In general, Drosphila spp. are very sensitive to desiccation. However, sensitivity to desiccation depends upon climatic conditions and flies could develop desiccation resistance over time (Davidson 1990, Bradley et al. 1999).

Like most Drosophila spp., reproduction in Drosophila suzukii is rapid. The total life cycle may be completed within one to two weeks depending upon the climatic conditions (Kanzawa 1939). Adult life span is about three to nine weeks. However, flies emerging late in the season overwinter and may live longer. In Japan, the fly produces 10 to 13 generations (Kanzawa 1939). Flies could survive up to 10 generations per year under California climate conditions (Walsh et al. 2011). The egg, larval and pupal stages last from 1–3, 3–13, and 4–5 days, respectively (Kanzawa 1939). Degree-day models on Drosophila suzukii suggest that the entire life cycle (egg to egg laying female) can be completed within 12 to 15 days at 18.3°C (65°F) or a little more than a week at 21.1°C (70°F) (Walsh et al. 2011).

A single female can lay one to 60 eggs per day and 200–600 eggs in her lifetime. A female lays approximately one to three eggs per oviposition site. The eggs are laid singly and are randomly distributed on fruits. Multiple clutches of larvae may be present on the same fruit because females may oviposit on the same fruit (Kanzawa 1939, Mitsui et al. 2006, Walsh et al. 2011).

Hosts (Back to Top)

Drosophila suzukii has a wide host range, including:

  • Cornus kousa, dogwood
  • Eugenia uniflora, Surinam cherry
  • Fragaria ananassa, strawberries
  • Morus spp., mulberry
  • Murraya paniculata, orange jasmine
  • Myrica rubra, Chinese bayberry
  • Prunus spp. – P. avium, sweet cherries; P. domestica, plums; P. persica, peaches
  • Pyrus pyrifolia, Asian pears
  • Ribes spp., currants
  • Rubus spp. – R. armeniacus, Himalayan blackberries; R. loganobaccus, loganberries; R. idaeus, raspberries; R. laciniatus, evergreen blackberries; R. ursinus, marionberries
  • Vaccinium spp., blueberry, cranberry
  • Vitis vinifera, wine grape

The following hard fruits may be attacked if the skin is already broken:

  • Actinidia spp., kiwi
  • Diospyros kaki, persimmons
  • Eriobotrya japonica, loquat
  • Ficus carica, fig
  • Lycopersicon spp., tomato
  • Malus domestica, apple
  • Pyrus spp., pear

Damage (Back to Top)

Fruit infestation is initially manifested by scars on the fruit surface left by ovipositing females (stinging). The initial oviposition site becomes sunken. Damage is caused primarily by larvae feeding on fruit pulp turning the fruit flesh brown and soft. The larger larvae cut breathing holes in fruit. Infested fruit collapse around the feeding site very rapidly and rot due to mold or secondary infections (Beers et al. 2010).

Figure 11. Oviposition scars from a female spotted-wing drosophila, Drosophilia suzukii (Matsumura), on a cherry fruit. Photograph by Martin Hauser, California Department of Food and Agriculture.

Management (Back to Top)

Monitoring and trapping. Management practices for spotted-wing drosophila are similar to those used to manage common Drosophila flies. Monitor adult fly populations before fruit begin ripening and before flies begin laying eggs. Bucket-style traps or quart containers used for monitoring other Drosophila flies can be effectively used for monitoring Drosophila suzukii. Mixtures of yeast, sugar, and water; fruit purees, distillates from apple cider vinegar or wine; ethanol, acetic acid, and phenylethanol in 1: 22: 5 ratios are potent baits for monitoring Drosophila suzukii populations. However, traps baited with yeast-sugar-water mixtures facilitate easy identification of flies because of the clear color of the bait material. Addition of a small drop of dish soap as a surfactant or placement of a sticky card within the traps improves trap efficiency by retaining the flies which have already entered the traps. The traps perform best when deployed under cool and shady areas in the field (Walsh et al. 2011).

Figure 12. Simple funnel trap baited with vinegar to trap adult Drosophila. Photograph by Whitney Cranshaw, Colorado State University, Bugwood.org.

Cultural control. Good field sanitation is critical to prevent further spread of flies. Ripe fruit should be picked frequently to minimize population buildup. All damaged fruit should be removed from the field and destroyed, either by burial or disposal in closed containers. Drosophila flies are weak fliers but spread easily through infested fruits or by wind. Therefore, all nearby sources of fruit should be managed to eliminate flies (Ministry of Agriculture and Lands, British Columbia 2009).

Biological control. Parasitoids from the families Braconidae and Cynipidae are potential biocontrol agents of Drosophila suzukii. Orius insidiosus has been reported to feed exclusively on Drosophila suzukii. (Kanzawa 1939, Dubuffett et al. 2009, Walsh et al. 2011). However, the role of beneficial organisms in management of Drosophila suzukii has not been fully ascertained (Walsh et al. 2011).

Chemical control. Insecticide sprays effective against other Drosophila flies are also effective against Drosophila suzukii adults. However, Drosophila suzukii’s preference for ripening fruit necessitates use of chemicals with shorter pre-harvest intervals (Walsh et al. 2011).

Selected References (Back to Top)

  • Beers EH, Smith TJ, Walsh DB. (August 2010). Spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilida). Orchard Pest Management Online. (3 March 2017)
  • Bradley TJ, Williams AE, Rose MR. 1999. Physiological responses to selection for desiccation resistance in Drosophila melanogaster. Integrative and Comparative Biology 39: 337-345.
  • Bolda MP, Goodhue RE, Zalom FG. (February 2010). Spotted wing drosophila: Potential economic impact of a newly established pest. Agriculture and Resource Economics Update. (no longer available online)
  • Davidson JK. 1990. Nonparallel geographic patterns for tolerance to cold and desiccation in Drosophila melanogaster and Drosophila simulans. Australian Journal of Zoology 38: 155-161.
  • De Camargo R, Phaff HJ. 1957. Yeasts occurring in Drosophila flies and in fermenting tomato fruits in Northern California. Journal of Food Science 22: 367-372.
  • Dubuffet A, Colinet D, Anselme C, Dupas S, Carton Y, Poirié M. 2009. Variation of Leptopilina boulardi success in Drosophila hosts: what is inside the black box? Advances in Parasitology 70: 147-88.
  • Green MM. 2002. It really is not a fruit fly. Genetics 162: 1-3.
  • European and Mediterranean Plant Protection Organization. (February 2010). http://www.eppo.org/QUARANTINE/Alert_List/insects/drosophila_suzukii.htm (3 March 2017)
  • Hauser M, Gaimari S, Damus M. (October 2009). Drosophila suzukii new to North America. North American Dipterists Society. (3 March 2017)
  • Kaneshiro KY. 1983. Drosophila (Sophophora) suzukii (Matsumura). Proceedings of Hawaiian Entomological Society 24: 179.
  • Kanzawa T. 1939. Studies on Drosophila suzukii Mats. Kofu. Review of Applied Entomology 29: 622.
  • Kimura MT. 1988. Adaptations to temperate climates and evolution of over-wintering strategies in the Drosophila melanogaster species group. Evolution 42: 1288-1297.
  • Markow TA, O’Grady PM. 2006. Drosophila: A Guide to Species Identification and Use. Academic Press, London. 272 pp.
  • Ministry of Agriculture and Lands, British Columbia. (December 2009). Spotted wing drosophila (Fruit fly) Pest alert. (3 March 2017)
  • Mitsui H, Achterberg VK, Nordlander G, Kimura MT. 2007. Geographical distributions and host associations of larval parasitoids of frugivorous Drosophilidae in Japan. Journal of Natural History 41: 1731-1738.
  • Molina JJ, Harisson MD, Brewer JW. 1974 Transmission of Erwinia carotovora var. atropeptica by Drosophila melanogaster Meig. American Potato Journal 51: 245-250.
  • Oku T. 2003. SWD: Drosophila suzukii (Matsumura) in Japan. Agricultural Pest Encyclopedia. Zenkoku Noson Kyoiku Kyokai 381 pp.
  • Price JF, Nagle CA. (November 2010). Spotted wing drosophila new in Florida berry culture. EDIS. (3 March 2017)
  • Steck GJ, Dixon W, Dean D. (August 2009). Spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera, Drosopilidae), a fruit pest new to North America. FDACS-Division of Plant Industry. (no longer available online)
  • Toda MJ. 1987. Vertical microdistribution of Drosophilidae (Diptera) within various forests in Hokkaido. III. The Tomakomai Experiment Forest, Hokkaido University. Research Bulletin of College Experiment Forests. 44: 611-632.
  • Walsh DB. (2009). Spotted wing drosophila could pose threat for Washington fruit growers. Washington State University Extension. (3 March 2017)
  • Walsh DB, Bolda MP, Goodhue RE, Dreves AJ, Lee J, Bruck DJ, Walton VM, O’Neal SD, Frank GZ. 2011. Drosophila suzukii (Diptera: Drosophilidae): Invasive pest of ripening soft fruit expanding its geographic range and damage potential. Integrated Pest Management 106: 289-295.

Spotted Wing Drosophila—Drosophila suzukii

The spotted wing drosophila (SWD) is a fruit fly orginally from Asia, was found in Hawaii in the 1980s, in California in 2008, in Michigan in 2010 and in Maine in 2012. It looks very much like other fruit flies, but unlike most fruit flies, which attack rotting or over-ripe fruit, SWD attacks healthy, undamaged fruit. It has the potential to be a serious pest of strawberries, raspberries, blackberries, blueberries and other soft fruit. To date it has not been found on cranberries, nor on hard fruits such as apples.

More information on fruit flies

The spotted wing drosophila adult is approximately 1/16 to 1/8 inches long (which is very, very small). The males can be identified by the dark spots on the wings; the females do not have these spots. The female uses a prominent, sawlike ovipositer to deposit eggs just under the skin of the fruit. Thread-like “breathing tubes” can sometimes be seen protruding from the fruit. Eggs hatch inside the fruit. The larvae are tiny, white, cylindrical maggots, approximately 1/8 inch long when fully grown.

Click on images to view full-size

Identification and Control Information (each will open in a new window)
  • Spotted Wing Drosopholia in the Northeast—Northeastern IPM Center
  • Spotted Wing Drosophila—Cornell University
  • Fruit Flies/Spotted Wing Drosophila Fact Sheets and Seasonal Update—University of Maine Cooperative Extension
  • Spotted Wing Drosophila—Maine Organic Farmers and Gardeners Association
  • Spotted Wing Drosophila Information—Michigan State University Integated Pest Management
  • Spotted Wing Drosophila Information—UMass Amherst Fruit Advisor

It is the policy of the State of Maine to minimize reliance on pesticides. The Maine Department of Agriculture and the Maine IPM Council encourage everyone to practice integrated pest management and to use pesticides only as a last resort. The mention of pesticides in the fact sheets linked to these pages does not imply an endorsement of any product. Be sure that any product used is currently registered and follow all label directions.

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