Ministry of Agriculture and Lands
Spotted Wing Drosophila (Fruit Fly) Pest Alert
December, 2009
The spotted wing drosophila fly, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) was first identified in the Western United States in late 2008. Since July 2009, it has been found in Florida, Oregon and Washington. It has been established in Hawaii since 1986. In September 2009, spotted wing drosophila was confirmed in the Fraser Valley area of British Columbia, and in October, it was confirmed in fly trap samples from a cherry orchard in the Central Okanagan Valley.
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.
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| 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 fore 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.
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).
Eggs: 0.6 mm long, oval, white, 2 filaments at one end (figure 4).
Refer to the Identification Guide for Spotted Wing Drosophila (PDF, 2.5 MB) for additional information on characteristics of this pest.
Distribution
Asia: Burma, China, India, Japan, Korea, Russia (far east), Thailand
Canada: British Columbia, coastal (Fraser Valley) and Central Okanagan
USA: California, Oregon, Washington, Florida, Hawaii
Hosts
To date in British Columbia, spotted wing drosophila have been confirmed infesting fall raspberry (Rubus), blueberry (Vaccinium), wild and cultivated blackberry (Rubus) and grape (Vitis). Fruit fly larvae were found in strawberry (Fragaria) and kiwifruit (Actinidia), but were not reared out to adults, so species was not confirmed. Additional hosts include dogwood (Cornus kousa), mulberry (Morus), cherry and other stone fruits (Prunus), and Myrica rubra.
Damage
In 2009, populations and fruit damage did not become evident until late in the season (August). 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 from the females’ egg laying activities are evident within the soft areas of infested fruit (figure 3). Besides contamination with larvae, these oviposition holes provide entry points for disease-causing organisms and secondary insects.
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| Figure 3. Spotted Wing Drosophila oviposition holes in blueberry | Figure 4. Spotted Wing Drosophila Eggs |
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| Figure 5. Spotted Wing Drosophila Larva in blueberry fruit |
Figure 6. Spotted Wing Drosophila-infested blueberry fruit with pupae |
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Figure 7. Spotted Wing Drosophila pupae. |
Life Cycle
Spotted wing drosophila overwinters as adult flies. In spring flies become active, mate and lay eggs in suitable 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 20oC 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 21-25 days at 15oC, 50 days at 12oC, 19 days at 18oC, 8.5 days at 25oC, and 7 days at 28oC. Adults are attracted to dropped and decaying fruit and will feed on it.
How it Spreads
Spotted wing drosophila adults can be blown by wind to nearby locations. However, long distance dispersal is expected to be achieved by 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, burying culls and keep processing areas and equipment free of old fruit. Please refer to the factsheets on management and sanitation linked below under "further information" for more details on managing this pest in tree fruit and berry crops.
Quarantine Regulations
We do not expect the United States to regulate this pest, as it is present in the major fruit growing regions. The Canadian Food Inspection Agency (CFIA) is reviewing this pest issue in order to determine if any regulatory actions in Canada are required to limit the spread and impact of this pest.
Surveillance
Surveillance will continue in fruit growing regions of B.C. in 2010 to determine more about its distribution and life cycle, including time of emergence and crops affected.
Spotted wing drosophila can be monitored with yeast, sugar, and water baited container traps, or by use of commercial fruit fly bait. Suspect fruit can be collected and inspected for larvae. Adult flies are needed to confirm species. See links below for further information on trapping and for updates on the surveillance programs.
If you think you have this pest, contact
- The BCMAL Plant Diagnostic Laboratory: The lab webpage includes information on collecting and submitting fruit samples
- Susanna Acheampong, Entomologist, BCMAL in Kelowna: 1-888-332-3352 or 250-861-7211
Further Information
