CORVALLIS, Ore. – Oregon State University has created a series of short videos to teach gardeners how to detect and manage a fruit-damaging fly that might be in their yards.
Filmed amid blueberry and raspberry bushes in her backyard, OSU Extension Service entomologist Amy Dreves demonstrates in the videos how to look for the spotted wing drosophila fly. This invasive vinegar fly was first documented in Oregon last year when it damaged berries and peaches. This year it has been reported at low levels in 15 counties in the state, including Benton, Linn, Jackson, Marion, Polk, Wasco and Yamhill, Dreves said.
It has also been seen this year in California, Florida, Washington and British Columbia, though only California has reported damage to fruit. "But it's still early in the fruiting season," Dreves said.
The fly is an economic threat to the fruit industry because it prefers intact, ripening fruit that is still on the plant whereas other vinegar flies favor overripe and decomposing fruit. The pest has been found on crops that include blueberries, blackberries, strawberries, cherries, peaches and grapes.
Dreves and her colleagues have been conducting research to help commercial growers combat this fly, but they also want gardeners to join the fight. The videos are the latest outreach tool and can be found at http://swd.hort.oregonstate.edu/gardeners. They're divided into seven topics that explain how to:
Drill several holes (3/8 to 3/16 inch) into the side of a 16- to 32-ounce plastic cup. The flies are attracted to the smell of apple cider vinegar, so pour about two inches of it into the container. Attach a strand of wire to the cup to hang it. Place a yellow sticky card (found at garden stores and nurseries) near the top of the cup by bending it in an arch. Or hang the card from a lid with a paper clip. Place the lid on the cup.
Prior to fruit set, hang the monitoring traps from bushes or trees or, in the case of strawberries, place them on the ground or on a brick in a cool, shady area.
Remove the sticky card and examine it closely for the spotted wing drosophila. Or filter the vinegar and look for the flies in the strainer. Once a week, replace the sticky card with a new one and change the vinegar. Document your findings.
Identify the fly
Use a hand lens to magnify key features. Unlike other vinegar flies, the male spotted wing drosophila has a black spot near the tip of each of its two wings. The female has a prominent saw-like organ on the end of her abdomen that deposits eggs into fruit. The eggs turn into larvae that eat the fruit. If you find a spotted wing drosophila, contact the OSU Extension office in your county for confirmation. Contact information for each office is at http://bit.ly/aDsOBu.
Set multiple traps
Place a series of closely spaced vinegar traps along the perimeter of your yard early in the season to catch potential spotted wing drosophila flies before they venture into your yard and infest your fruit.
After fruit sets and while it's still green, drape and secure whole plants with fine netting (you may want to use hoops as a frame). Or tie fine-sleeved netting or breathable bags (like the kind used to strain paint) over individual clusters of fruit. Another option is to slip nylon footies (the kind in shoe stores) over the fruit. Cover plants before any flies land on them and lay eggs.
Clean up fallen fruit
If your fruit falls on the ground, pick it up, compost it or smash it into the ground so spotted wing drosophila flies don’t have a place to lay eggs and so any possible larvae already in the fruit will die.