Since the start of its invasion in 2008/2009, the spotted wing drosophila, which is originally from Asia, has spread extensively in North and South America and Europe where it has caused severe yield losses in many berry crops, cherries and grapes.
Life cycle and appearance of Spotted wing drosophila
Adult spotted-wing drosophila are small, 2-3 mm in lengthg, and have a wingspan of 6-8 mm. Males are smaller than females. They can be easily distinguished from males of other Drosophila species or SWD females by a large dark spot on each wing, where their common name is derived from. Females have a strong saw-like ovipositor that is used to penetrate the skin of the host fruit and for laying the egg into the fruit. Eggs are white, 0.6 long and 0.2 mm wide. Each egg has two respiratory tubes which stick out of the fruit. There are three larval instars and in the third instar larvae are about 3.9 mm long. The pupae of Drosophila suzukii are tan-brown and 3 mm long.
Contrary to other Drosophila species, D. suzukii females lay their eggs into healthy, unripe fruits. The larval development takes place in the fruit. The larvae pupate either fully or partly in the fruit, or outside the fruit on the ground.
After oviposition, the respiration tubes extend from the fruit but are difficult to see. Larval feeding in the fruit leads to fruit tissue collapse. Even if the fruits have not collapsed, the occurrence of larvae within the fruit makes them unmarketable. The punctures made by the oviposition by D. suzukii exposes fruits to secondary pathogens (e.g. bacteria, fungi and yeasts). Finally, deterioration of fruit can increase its susceptibility to attack by other Drosophila species. D. suzukii has a wide host range, with thin-skinned berries (e.g. raspberries, blackberries, blueberries, strawberries) and stone fruits (e.g. cherries, plums) being particularly susceptible to infestation.