The following images illustrate some key traits for the identification of SWD adults that should be visible using a hand lens. Both sexes have red eyes and dark, unbroken bands across the top of the abdominal segments. Males are most easily recognized by their dark spot near the tip of the wing (Figure 2). The spot typically covers the area from the leading edge to the second vein. The males also possess combs of thickened hair on the first two tarsal segments of the front legs.
The SWD eggs hatch in 1 to 3 days and the larvae, also referred to as maggots, feed in the fruit for about a week, pupate and then emerge as adults anywhere from 4 to 15 days later. This short life cycle from egg to adult means we will have to deal with many generations in a year. In addition to maggots inside the fruit, another problem associated with the SWD is the introduction of bacteria and fungi into the fruit when they lay eggs, leading to fruit rot.
Adult flies insert eggs into soft fruit where the larvae develop (Figure 3). The larvae eventually leave the fruit and drop to the ground where they pupate. They later emerge as adults. SWD can complete its life cycle in as little as 7-10 days, although in cooler weather it could take up to 25 days or longer.
SWD larvae feed on healthy, intact, ripening fruits. In particular, SWD will feed on thin-skinned, soft fruits such as raspberries, blackberries, blueberries, strawberries, grapes, plums and cherries. These are mainly soft skin fruit which Aronia is not. This fact allows the SWD to feed on other berries first then move to aronia berries later. Not everyone will have an infestation of SWD. But you will not know you have them unless you set traps and monitor them weekly.
Web site resources:
“Managing Spotted Winged Drosophila in Commercial Fruit Production” - free download from ISU included in this download are common products, their effectiveness, residual activity, and pre-harvest interval.