Blueberries: Spotted Wing Drosophila

The spotted wing drosophila is a vinegar or fruit fly of East Asian origin. Unlike other fruit and vinegar flies, which lay their eggs on past ripe or rotting fruit, they lay their eggs inside fresh fruit, often before harvest. Aside from the superficial scars left by the female’s ovipositor (their egg-laying device), most damage is done by the larvae feeding inside the fruit. After only a few days, the fruit skin becomes dimpled or wrinkled, forming craters in the fruit, and making it susceptible to decays and rots. It is possible, however, for early-stage larvae or eggs to leave no visible impact on the fruit.

Picked blueberries with one white, oval-shaped larva sitting on surface of blueberry. An arrow points to the larva.
Spotted wing drosophila larva.
Blueberry with insect sitting on surface. Insect is fly with orange head and abdomen and translucent, iridescent wings. Fly has red eyes.
Adult male spotted wing drosophila.

More information:

Male SWD have one dark spot on the distal upper section of each wing, and two dark comb-like structures on each foreleg. Female SWD have no dark spots on wings, and have saw-like serrations on ovipositor. Male SWD can be identified without a microscope because of the distinctive spot on each wing.
A guide to visual identification and gendering of spotted wing drosophila, courtesy of M. Hauer