Scientists use samba wasps to manage the invasive spotted-wing drosophila, a key pest of small andstone fruit worldwide
By Vaughn Walton
Recently, spotted-wing drosophila (Drosophila suzukii, SWD) has appeared in fruit production areas worldwide. This invasive pest that resembles a vinegar fly, is highly damaging to berries and stone fruits. This fly infests these fruits as they ripen, costing half a billion dollars of crop damage annually in the USA. Affected crops include strawberry, raspberry, blackberry, blueberry, cherry, and wine grape.
Most vinegar flies attack overripe fruit laying eggs in the soft fruit. Spotted-wing drosophilhas a saw-like ovipositor, and can lay its eggs into ripening, susceptible fruit. The saw-like ovipositor allows SWD to cut into the firm outside of fruit and push its eggs in. These eggs are laid directly under the fruit surface area and immediately, sometimes even within hours, start to hatch. Hatching larvae will start feeding on the pulp of the affected fruit. Within two or three days, feeding larvae soft-en the pulp and provide entry to microorganisms, resulting in unacceptably soft and spoiled fruit. Within a one-week period, under ideal conditions, larvae will emerge from fruit. Emerging SWD larvae can pupate either in fruit or outside, after which adults emerge to repeat the life cycle. The life cycle can be completed within as little as ten days, with up to ten generations per season, resulting in explosive pest populations.
Scientists are researching control measures for SWD. One possibility for control includes the release of insect predators. In Oregon, USA, during summer of 2022, scientists are releasing a parasitoid wasp, also called the samba wasp (Ganaspis brasiliensis) as a predator, to combat the highly damaging and invasiveness, spotted-wing drosophila (Drosophila suzukii, SWD). Samba wasp releases in the Willamette Valley are part of a worldwide bid to help manage SWD. Samba wasp is also being evaluated by Kent Daane at UC Berkeley, so keep your eye on what's going on in California, as well.
Read the Samba Story. Images supplied by Vaughn Walton