Fact Sheet FS1246
Spotted-wing drosophila (SWD), Drosophila suzukii Matsumura, is an invasive vinegar fly that damages a wide range of fruit crops, including blueberry, grape, cherry, raspberry, blackberry, and strawberry. Native to Southeast Asia, SWD was first detected in the continental United States in 2008 and has since become established in many states. It was first recorded in New Jersey in July 2011. Unlike most of its fruit fly relatives, SWD poses a significant threat because females possess a large, serrated ovipositor capable of piercing the skin of ripening soft fruits to lay eggs. The larvae rapidly develop inside the fruit, causing puncture wounds, softening, wrinkling, fruit collapse, and contamination with larvae.
Figure 1. Male and female spotted-wing drosophila. Photo courtesy of John Obermeyer, Purdue University.
Identification
SWD adults are small flies, measuring approximately 2.5–3 mm (~0.1 inches) in length, with light yellow to brown bodies and red eyes. Males are easily identified by a distinctive black spot near the tip of each wing and two black bands on their front legs (Figure 1). Females are slightly larger than males and are equipped with a prominent, serrated ovipositor used to pierce the skin of ripening fruit (Figure 1).
SWD eggs (Figure 2) are white, oval-shaped, and feature two filament-like structures at one end. They are laid either on the surface or just beneath the skin of the fruit. The larvae (Figure 2) are legless, white, and cylindrical, with two finger-like projections (spiracles) at one end and dark mouthparts at the other. Pupae (Figure 2) are football-shaped and initially transparent, gradually turning dark brown with visible red eyes. They also have two projections at the head end.
Life Cycle
Figure 2. Spotted-wing drosophila life cycle. Photo courtesy of John Obermeyer, Purdue University.
SWD overwinters as an adult and becomes active in the summer to mate (Figure 2). During the summer and fall, females lay eggs in ripening, susceptible fruit. A key difference between SWD and other vinegar flies is that SWD attacks fruit before it is fully ripe. A single female can lay up to 350 eggs in her lifetime (Figure 2). The life cycle duration ranges from 8 to 14 days, depending on temperature, with adult lifespans in mid-season lasting 3 to 9 weeks (Figure 2). SWD is most active at temperatures between 68–86°F. Eggs hatch within 12 to 72 hours. Larvae develop inside the fruit for 5–7 days before pupating; pupation, which can occur either inside or outside the fruit, lasts 4 to 15 days.
In New Jersey, SWD is typically detected in fields by mid-June, with fruit infestations occurring around the same time. For fruit production, this means that early-ripening varieties—such as Duke blueberries, southern cherries, June-bearing strawberries, and early summer raspberries—are generally not affected by SWD but should still be monitored. Summer-ripening varieties of all berry crops are considered susceptible and require close monitoring. Late-season blueberries, blackberries, and fall-bearing raspberries are highly susceptible to SWD in New Jersey, largely due to the large populations present during their ripening period. While wine grapes in the state have not been significantly impacted, SWD can attack wine grapes after veraison, and infestations can occur when fruit has been previously damaged—for example, by bird injury.
Monitoring
Figure 3. Example of trap for monitoring SWD.
Early detection is critical for effective SWD management. Monitoring traps should be placed in the field at least two weeks before fruit begins to ripen and checked weekly. Traps should be positioned at fruiting height near developing fruit, ideally along field edges adjacent to wooded areas. Traps can be commercially purchased or made by hand. One of the most effective and widely used designs consists of a red sticky card baited with an SWD lure (Figure 3).
Two commercial SWD lure options are available: Pherocon SWD lures and traps (Trécé) and Scentry SWD lures and traps (Great Lakes IPM). Examine the sticky cards for both male and female SWD (Figure 4). Males are easier to identify due to the characteristic black spots on their wings. Females are more difficult to recognize, as the serrated ovipositor may be retracted into the abdomen; gently pressing on the abdomen can help extend it for identification. Once SWD has been confirmed in a field, monitoring can be simplified by focusing on male counts, which are generally representative of the overall population.
Salt Flotation Test
A simple salt flotation test can be used to inspect fruit for SWD larvae (see demonstration video: Salt Flotation Method to Monitor SWD Larvae (YouTube video). This method is useful for evaluating the effectiveness of your SWD management program, determining infestation levels, and deciding when to initiate control measures.
To perform the test, place berries in a large, sealable plastic bag and gently crush the fruit. Add a saturated salt solution (e.g., 1 cup salt per gallon of water) to the bag and let it sit for 4–5 minutes. The saltwater irritates the larvae, causing them to exit the fruit and float to the surface. Pour the contents through a fine coffee filter to collect and observe any larvae that have emerged.
Control
Figure 4. Spotted-wing drosophila on yellow sticky card. Photo by John Obermeyer, Purdue University.
Sanitation is a critical component of SWD management. Like other vinegar flies, SWD thrives on rotting fruit. Populations can increase rapidly after harvest, due to the abundance of fallen and overripe fruit, which serve as both food and breeding sites. To reduce these resources, fruit should be harvested thoroughly, rows kept clean, fallen berries covered, and culled fruit either buried or disposed of properly.
Biological control efforts are underway with the release of Ganaspis kimorum, a larval parasitoid of SWD native to Asia. This parasitoid shows promise for reducing SWD populations by targeting larvae developing inside fruit, particularly in non-crop habitats. Behavior-based control strategies, such as attract-and-kill and push-pull systems, are also being investigated. However, these approaches are still in the research and development phase and are not yet widely adopted or commercially available. At present, SWD management continues to rely heavily on insecticides, which remain the primary tool for protecting susceptible fruit crops.
Several classes of insecticides are labeled for SWD control, including: spinosyns (IRAC Group 5), pyrethroids (Group 3), anthranilic diamides (Group 28), carbamates (Group 1A), and organophosphates (Group 1B). Insecticide applications should begin when fruit becomes susceptible—typically at the onset of ripening (i.e., when fruit starts to change color)—and continue at 7-day intervals during the harvest period. Starting with the most effective insecticide can help suppress early population growth. To prevent resistance development, rotate insecticides with different modes of action.
SWD are highly sensitive to desiccation and tend to seek shelter in shaded, humid areas such as the plant canopy and undergrowth. Therefore, applications made at dusk with full foliar coverage are likely to be most effective. Proper pruning and canopy management can further improve spray penetration and overall control.
Additional Resources
This revised fact sheet is based on the original work of:
Caryn Michel, Former Ph.D. Candidate at Rutgers
Cesar Rodriguez-Saona, Extension Specialist in Blueberry and Cranberry Entomology
Anne Nielsen, Extension Specialist, Entomology
Dean Polk, Agriculture & Natural Resources County Agent and Fruit IPM Coordinator, Retired
September 2025
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