New England fruit growers have another fruit pest to scout for and control. That's the word from Vern Grubinger, Extension vegetable and berry specialist at University of Vermont.
The spotted wing drosophila has arrived. This tiny insect feeds on many different cultivated and wild fruits, but is a particular threat to soft fruits that ripen in the late summer and fall, says Grubinger. "SWD is likely to be a significant problem in small fruits such as blueberries, fall raspberries and grapes as well as tree fruits including peaches and cherries."
It was first discovered on the West Coast in 2008 and quickly moved to the East Coast. By last year, it was widespread in Pennsylvania and parts of New York. Even today, says the berry specialist, little is known about how big an impact it'll have and what management tactics will be most effective.
SWD looks very similar to the fruit flies that feed on and fly around overripe fruit on a kitchen counter. However, unlike these flies, it feeds on healthy, intact fruits as they ripen. Once a crop has finished fruiting, the flies move on to other crops.
Hard to ID
A hand lens or microscope is needed to see its identifying features. It's only one-twelfth to one-eighth inch long, but has yellowish-brown coloration and prominent red eyes. Males have a dark spot near the edge of each of their clear wings.
If you see fruit flies swarming in the evening around ripening fruit, you probably have SWD. To date, they have only been found outdoors.
Females puncture firm, ripening fruit and deposit eggs that quickly hatch into small larvae that feed inside the fruit, causing discoloration and decay. Sometimes these symptoms won't show up until after harvest. In addition to the damage from larvae, infested fruit becomes susceptible to fungi and bacteria that cause softening and rot.
Populations can build up into fall. It overwinters as an adult. Since it has overwintered successfully in Michigan, it's likely to survive here, too.
How to manage
Timely harvest and sanitation are important to reduce SWD population buildup. This means frequent picking of a crop to ensure ripe fruits are removed from the field as soon as possible and removing and destroying old fruit remaining on stems.