Spotted wing drosophila

Identification & Biology
Latin Name : Drosophila suzukii
Category : Insects & Spiders
Description :

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, spotted wing drosophila 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, 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. 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. Larvae: Legless, headless, up to 6 mm long at maturity, white or transparent. Pupa: 3 mm long, brown, football-shaped, two stalks with small finger-like projections on one end. Spotted wing drosophila emerging in the fall overwinter as adult flies. In spring flies become active, mate and lay eggs in ripening fruit.

Habitat

Spotted wing drosophila was first identified in British Columbia in 2009. It is now widespread in Coastal and Interior fruit growing areas of B.C. In BC, spotted wing drosophila has been confirmed infesting wild and cultivated raspberry and blackberry, blueberry, strawberry, cherry, peach, nectarine, apricot, plum, and suspected in hardy kiwifruit. 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).

Impact & Risks

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. Larvae hatch and 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. 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.

Prevention & Mitigation

Management recommendations include registered insecticides, good harvest and sanitation practices, such as culling soft fruit, destroying culls, and keeping processing areas and equipment free of old fruit.

Okanagan Distribution

Priority Level Definitions

Watch For - Poses a significant threat (very high risk) and does NOT presently occur in the region OR is relatively new to the region and is very limited in extent.
High - High risk/impact; limited population with significant potential to spread in the region.
Medium - Medium risk/impact; limited distribution – broader population distribution with potential to spread further in a region.
Low - Low risk/impact; may be widespread or not, may be of concern in specific situations with certain high values – e.g. specific agriculture crops. Some species may be treated primarily with biological control agents.