Spotted wing drosophila
(Drosophila suzukii)

Pest Overview
Spotted Wing Drosophila (SWD) is an aggressive pest that primarily targets soft-skinned fruits. Crops affected by SWD include cane berries (raspberries, blackberries), strawberries, blueberries, cherries, and select stone fruit varieties. Unlike other common Drosophila fruit flies that only attack overripe or damaged fruit, female SWD have serrated ovipositors, which allows them to deposit eggs directly into healthy, ripening fruit. This causes significant crop damage in the field and leads to entire loads of rejected fruit. Early detection, monitoring, and effective treatments are critical for SWD control to minimize crop damage.

Geographic Distribution
Originally an invasive pest of Southeast Asia origins, Spotted Wing Drosophila has rapidly spread across the globe, with significant populations now found in North America, Europe, and parts of South America. In the United States, it was first discovered in California in 2008 and has since established itself in all major berry production regions of the state. Other impacted areas of the US include Utah, Minnesota, Michigan, Missouri, Louisiana, West Virginia, Pennsylvania, North Carolina, South Carolina, and Florida. Temperature ranges for SWD development align with growing requirements for most berry crops, making them ideal hosts for the pest.
Economic Impact
Spotted Wing Drosophila poses a significant risk to the fruit industry. Because SWD populations target market-ready fruit, they compromise crop quality leading to a higher risk of rejected fruit and increased production costs for growers. Wounds caused by SWD oviposition and feeding leave fruit susceptible to pathogens like bacteria or fungi in the environment, further degrading crop quality. Economic damage varies depending on the growing region and crop, but severe yield losses exceeding 80% have been reported.
Insecticide programs vary between operations. Growers in California often make weekly applications throughout the entire growing season to achieve acceptable control, accelerating eventual insecticide resistance. This is not only a tremendous economic cost, but also creates difficulties during harvests due to pre-harvest and re-entry intervals Insecticides leave fruit at high risk for exceeding the stringent regulations on maximum residue levels.

Spotted Wing Drosophila have four life stages: egg, larva, pupa, and adult, and multiple generations per growing season. Adult females deposit eggs in fruit and the subsequent larval feeding directly damages the crop and allows entry points for diseases. SWD is unique among Drosophila species (commonly referred to as vinegar flies or fruit flies) because it utilizes fruit much earlier in the crop life cycle, differentiating it from other less damaging fruit flies that feed exclusively on over ripe or rotting fruit.
Egg Stage:
Female SWD are capable of laying an estimated 200-400 eggs in their lifetime and use a specialized, serrated ovipositor to deposit them into the flesh of fruit. Damage at this life stage is not immediately apparent as eggs beneath the fruit’s surface are difficult to detect. Eggs typically hatch in 1 to 3 days.
Larval Stage:
Post eclosion (egg hatch), SWD larvae begin to internally feed on fruit. Feeding at this stage renders fruit unmarketable, as it causes clear signs of deterioration such as softening, discoloration, and structural breakdown. Punctures from the ovipositor and larval feeding also create entry points for pathogens. Larvae typically complete development in 5 to 7 days, depending on temperature.
Pupal Stage:
Depending on infestation level, larvae can remain in fruit and progress to the pupal stage or will exit the fruit to continue its development. Pupae are more susceptible to environmental conditions and require protected spaces (like the inside of fruit or burrowed into soil) to mature into adults. This process can take approximately 4 to15 days.
Adult Stage:
Once adults emerge, they mate and female SWD will begin seeking out fruit to lay their eggs. SWD reproduce quickly, with the potential for multiple successive generations in a short time frame. Adults of this species are 2 to 3 mm long, have a light brown body, red eyes, and spotted wings (males only). SWD adults typically live for two to nine weeks depending on crop and temperature, and in California can have 10 or more generations.


BioMagnet™ Ruby
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The incorporation of BioMagnet™ Ruby in a comprehensive IPM program cuts SWD damage by an average of 75% or more
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