Ministry of Agriculture

Spotted Wing Drosophila (Fruit Fly) Pest Alert

Updated: June 9, 2014

Spotted wing drosophila (Drosophila suzukii), a serious new fruit fly pest of soft fruit and berries, was first identified in British Columbia in 2009. It is now widespread in Coastal and Interior fruit growing areas of B.C.

Spotted wing drosophila is a temperate fruit fly, native to Southeast Asia; preferring temperatures of 20-30 oC.  It is known to infest thin-skinned fruit.  Many species of fruit flies are present in late summer; most normally infest overripe, fallen, decaying fruit, so are not crop-limiting pests. However, a spotted wing drosophila female lays her eggs inside sound fruit before harvest with her saw-like ovipositor, which contaminates fruit with larvae, and causes it to become soft and unmarketable. 

Monitoring Reports
Management
Identification
Home Garden
spotted wing drosophila female spotted wing drosophila adult male
Figure 1. Spotted Wing Drosophila Adult Female. Inset shows ovipositor.
Photo Credit: Sheila Fitzpatrick, Agriculture & Agri-Food Canada, Pacific Agri-Food Research Centre, Agassiz
Figure 2. Spotted Wing Drosophila Adult Male with wing spots
Photo Credit: Sheila Fitzpatrick, Agriculture & Agri-Food Canada, Pacific Agri-Food Research Centre, Agassiz

Appearance

Many features are typical for Drosophila fruit flies, with a few key differences.  Male and female characteristics are key identifiers for this species.

Adults: 2-3 mm (1/8 inch) long, brownish with red eyes and clear fly-like wings.  Compared to other fruit flies, D. suzukii is a robust fly, but this is difficult to discern unless compared directly to other species.  Males have a black/grey spot on the end of each wing (figure 2), as well as two black ‘combs’ or bands on the front legs.  The females do not have spots or leg bands.  Females have saw-like ovipositors that are used to cut into fruit skin (figure 1).  Ovipositors are easier to see when extended.  A hand-lens or dissecting microscope is needed to confirm ovipositor presence. 

Eggs: 0.6 mm long, oval, white, 2 filaments at one end (figure 3, 4).

Larvae: Legless, headless, up to 6 mm long at maturity, white or transparent (figure 5).

Pupa: 3 mm long, brown, football-shaped, two stalks with small finger-like projections on one end (figures 6 & 7).

Refer to the Identification Guide for Spotted Wing Drosophila (PDF, 2.5 MB) for additional information on characteristics of this pest.

Distribution

SWD continues to spread, and is now widely distributed globally in most temperate soft fruit producing areas. Notable exceptions are South America, New Zealand and Australia, where SWD is not known to be established. Below is an approximate list of places where SWD is established.

Asia: Burma, China, India, Japan, Korea, Russia (far east), Thailand, Taiwan, Pakistan, Myanmar
North America: Canada, United States, Mexico
Europe: Spain, Russia, France, Italy, Portugal, Germany, Slovenia, Switzerland, Croatia, Belgium, Austria, United Kingdom, Netherlands

Hosts

In British Columbia, spotted wing drosophila has been confirmed infesting wild and cultivated raspberry and blackberry (Rubus), blueberry (Vaccinium), strawberry (Fragaria), cherry, peach, nectarine, apricot, plum (Prunus), and suspected in hardy kiwifruit (Actinidia).  Wild hosts confirmed in Coastal B.C. include Oregon grape (Mahonia aquafolium), elderberry (Sambucus), currant (Ribes), dogwood (Cornus kousa), mulberry (Morus), salmonberry (Rubus spectabilis), thimbleberry (Rubus parviflorus), salal (Gaultheria shallon), Indian plum (Oemleria cerasiformis) wild Prunus species, and red huckleberry (Vaccinium parvifolium). In Interior B.C, wild hosts confirmed include Oregon grape (Mahonia sp.), blue elderberry (Sambucus cerulean), Northern black currant (Ribes hudsonianum), Tatarian honeysuckle (Lonicera tatarica), Mahaleb cherry (Prunus mahaleb), and golden currant (Ribes aureum) (H. Thistlewood, AAFC, Summerland).

Damage

Females lay eggs under the skin of ripe fruit shortly before harvest. Larvae hatch and begin to feed within the fruit, causing softening in the area of feeding. There can be several larvae in a fruit, which hastens softening and fruit collapse. Holes the size of pin pricks are evident within the soft areas of infested fruit (figure 3). These holes result from egg laying and are used as breathing holes by larvae. In addition, these holes provide entry points for diseases such as brown rot and botrytis.

Drosophia suzukii eggs in blackberry Spotted wing drosophila eggs
Figure 3. Spotted wing drosophila eggs in blackberry fruit
Photo Credit: Dr. Ward Strong, FLNRO, Kalamalka Forestry Centre, Vernon
Figure 4. Spotted wing drosophila egg
Photo Credit: Brigitte Rozema & Howard Thistlewood, Agriculture & Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland
spotted wing drosophila larva Spotted Wing Drosophila pupae
Figure 5. Spotted wing drosophila larva in blueberry fruit

Figure 6. Spotted wing drosophila-infested blueberry fruit with pupae  

drosophila pupae spotted wing drosophila damage to blueberry fruit
Figure 7. Spotted wing drosophila pupae Figure 8. Spotted wing drosophila damage in blueberry

 

Life Cycle

Spotted wing drosophila emerging in the fall overwinter as adult flies. In spring flies become active, mate and lay eggs in ripening fruit.  Based on climate model predictions, there could be up to 5 generations per year in B.C.  Generations will likely be overlapping as flies are relatively long-lived particularly at temperatures of 20°C and cooler.  Based on a Japanese publication (Kanzawa 1939), oviposition lasts 10-59 days, with 7-16 eggs laid per day, and averaging 384 eggs per female.  Eggs hatch in 2-72 hours, larvae mature in 3-13 days, and pupae reside in fruit or outside of fruit for 3-15 days.  In the lab at constant temperature, one generation takes 50 days at 12°C, 21-25 days at 15°C, 19 days at 18°C, 8.5 days at 25°C, and 7 days at 28°C.  Adults are also attracted to dropped and decaying fruit and will feed on it. SWD will complete its development in dropped fruit.

How it Spreads
Spotted wing drosophila adults can be blown by wind to nearby locations.  However, long distance dispersal is through transportation of infested fruit to new regions.  Non-fruit bearing plants are not considered to be of significant risk to transport this pest.

Management

Management recommendations include good harvest and sanitation practices, such as culling soft fruit, destroying culls, and keeping processing areas and equipment free of old fruit. Please refer to the factsheets on management linked below under “further information” for more details on managing this pest in berry and tree fruit crops.

Emergency registration products approved for the control of spotted wing drosophila in B.C. for the 2013 season are Delegate (spinetoram), Entrust (spinosad), Malathion (malathion), Pyganic (pyrethrins) and Ripcord (cypermethrin). Both Entrust and Pyganic are acceptable for organic crop production. Labels are posted at: Current Emergency Registrations for British Columbia.

Quarantine Regulations
This pest is not regulated in the United States and Canada.  The regulatory status of this fly in other countries should be checked with packers.

Surveillance
Area-wide surveillance with apple cider vinegar traps in British Columbia for SWD indicates that flies are present and active throughout the year in the Fraser Valley, though numbers are very low in February through May. In the fruit growing interior regions, SWD can be caught in traps from May until November. Surveillance continues in fruit growing regions of B.C. in 2013 to determine when SWD flies are active in commercial fields.

Spotted wing drosophila flies can be monitored with apple cider vinegar baited cup-traps. Other bait types will work but B.C. experience indicates that apple cider vinegar is easy to use and effective. Suspect fruit can be collected and inspected for larvae. Adult flies are needed to confirm species. See Update on Spotted Wing Drosophila Trapping in Coastal British Columbia (Berry Crops) and Spotted Wing Drosophila Monitoring Report and Updates for Southern Interior of British Columbia for further information on trapping and for updates on the surveillance programs.

If you have questions about this pest, contact

Further Information

British Columbia

Information from Other Areas