Follow these helpful steps to thwart the tiny fruit fly that can turn your berries into mush.
A tiny fruit fly, the Spotted-wing Drosophila, can wreak havoc on your raspberries and other soft fruits at harvest time. We’ll teach you how to thwart its spread, starting with a simple, homemade trap.
Flocking to the feast
of luscious ripe raspberries, dripping like jewels from the canes, is no longer reserved just for the gardener who grew them. Enter the Spotted-wing Drosophila (SWD), a relatively new invader of the insidious sort that attacks fruit from the inside out. How? The tiny fruit fly, unlike its pesky cousin that lays its eggs on damaged or overripe fruit, lays its eggs in harvest-ready fruit. The eggs hatch as early as 12 hours later with ravenous larvae gobbling their way out to start another life cycle, leaving a cratered, bleeding berry behind.
First noticed in 2008, SWD has since spread throughout the country infesting late-summer, soft-fleshed fruits— raspberries being their favorite victim.
Follow our effective strategy to combat the insects that leave deformed or collapsed berries from otherwise-healthy plants: First, build a simple trap to catch and verify that it is SWD, then follow through with organic or traditional methods to thwart this pillaging pest.
Is your fruit infested with SWD? If raspberry canes and leaves are flourishing yet berries seem mushy, moldy, or crawling with white larvae, you’ll need to confirm that SWD is the culprit. Start by trapping and identifying the pest. Although you can purchase special traps, a homemade one also works well. Our Big Red Trap is made of everyday materials and is very effective in luring the tiny insect to its watery demise with a simple vinegar and soap solution.
Hang the Big Red Traps, one trap about every 6 feet, from poles nestled mid-height within the berry branches. Initially check the trap daily to collect and identify this spotted-wing pest, as its name suggests, by the male’s single black spot on the tip of each wing. Both the male and female have distinct red eyes and are about 2–3 millimeters long.
If SWD is in residence, continue trapping and monitoring, cleaning out the trap once a week and refreshing the bait.
While the Big Red Trap is useful for identifying, monitoring, and ridding your garden of some SWD, it isn’t the end-all solution to totally eliminating the pest. To further protect your harvest, some elbow grease is in order.
Mow fall-bearing raspberries down to the ground after frost, and clear the bed of debris where SWD love to hibernate. When canes begin to grow in spring, prune to no more than four or five healthy canes per linear foot, as this allows for optimum air and sunlight to circulate through the branches. Trellising also gives canes a lift and makes daily “clean” picking so much easier, and patrolling for just-ripe berries will keep you one step ahead of SWD.
If all else fails, organic insecticides are available. Spinosad, made from bacteria found in soil, has been found to be most effective in controlling SWD. (As with all insecticides, read and follow manufacturers’ directions carefully.)
SPOTTEDWING DROSOPHILA AND THE DAMAGE IT CAUSES