Spotted wing drosophila in pictures

Spotted wing drosophila (Drosophila suzukii) is a vinegar fly that can lay its eggs in undamaged fruit. This distinguishes it from other drosophilids, such as the common fruit or vinegar fly (Drosophila melanogaster) and the African fig fly (Zaprionus indianus), that lay eggs in damaged and decaying fruit.

The damage caused by spotted wing drosophila is similar to that caused by tephritid fruit flies such as Medflies (Ceratitis capitata) and Oriental fruit flies (Bactrocera dorsalis).

Hot and cold

Various studies have found that spotted wing drosophila can lay eggs at temperatures of 5–35 °C. The range for development of eggs to adults is 8–33 °C, with the optimum at 19–25 °C. Adult survival and development success are poor above 30 °C.

The development of all life stages is slower at low temperatures and faster at high temperatures. This is why the literature shows widely differing development times.

The adult flies can survive extreme cold. They are reported to damage apricots in the high-altitude Ladakh region in India, the second-coldest inhabited place in the world, with temperatures far below freezing for four months of the year.

Washington State University researchers found that females survive extended cold periods better than males. Females in winter diapause can resume egg-laying as soon as the weather warms.

Less is known about spotted wing drosophila’s heat tolerance. Although the insects are supposedly sensitive to high temperatures, they have successfully established in many hot places, including Spain and California.

High relative humidity favours spotted wing drosophila, especially under warm conditions. Adult flies can adapt to hot environments by sheltering in dense vegetation with higher humidity during the warmest part of the day.

Distribution

After spotted wing drosophila was initially discovered, Hortgro, SATI, SA Wine, and BerriesZA collectively funded a trap network. This included traps in the Orange and Olifants River regions, but spotted wing drosophila was not detected in these regions.

Surveillance in the major deciduous fruit-production regions in the 2024–2025 season continues as part of a collaboration between Hortgro and the FruitFly Africa Centre for Excellence in Monitoring.

Figure 1. The Hortgro trap network for 2024–2025.

Figure 2. The known South African distribution of spotted wing drosophila at the end of January 2025.

There is more about spotted wing drosophila (and other invasive pests and diseases) in the June 2022 issue of Fresh Quarterly.