Farmers who want to reduce their reliance on pesticides in fighting the spotted wing drosophila can learn about biological control methods during an upcoming workshop.
Experts from Oregon State University, Washington State University and the National Research Council of Italy will provide growers with advice on the invasive fruit fly at an Aug. 4 event organized by the Northwest Center for Alternatives to Pesticides in Eugene, Ore.
Fruit producers want as many weapons as possible in their battle against spotted wing drosophila due to worries that the insect will eventually develop a tolerance to commonly-used pesticides, said Amy Dreves, an OSU Extension entomologist specializing in integrated pest management.
“People are looking for what else is out there,” she said.
The flies thrive in humid conditions, which farmers can reduce by using drip irrigation instead of overhead sprinklers, Dreves said.
Pruning the canopy of crops, such as caneberries, can improve aeration to the detriment of the spotted wing drosophila, she said. Researchers are still examining the best pruning techniques to avoid denting yields.
“They are not sun baskers,” she said.
Thoroughly harvesting early season fruit will eliminate refuges from which the species can launch new offensives against mid- and late-season crops, Dreves said.
“That becomes the breeding source for the next harvest,” she said.
Similarly, farmers can try to limit spotted wing drosophila populations in nearby sites where they lay eggs on wild-growing plants such as Himalayan blackberry, dogwood and honeysuckle, Dreves said.
Placing a large number of traps within those “non-crop egg-laying sites” can kill the insects and steer them away from marketable fruit, but if farmers opt to remove the plants, they should replace them with flowering species, she said.
Parasitic wasps that feed on the fruit flies also require flowers for nectar and pollen, Dreves said. “We will talk about how to enhance the environment for them.”
In some cases, farmers are netting their crops after bloom to prevent the insects from infiltrating fruit, while others use special vacuums to collect the flies, she said.
Those options are expensive, though, and may not pencil out financially for all growing systems.
Regularly setting lures and traps to monitor fly populations allows growers to identify “hot spots” in their fields and evaluate how well treatments are working, she said.
By checking traps over last winter, researchers knew that mild conditions were permitting increased survival, leading to elevated populations this growing season, for example.
“It’s a means of helping you dictate what happens next,” Dreves said. “You can notice the shift in abundance.”
Spotted wing drosophila workshop
Date: Aug. 4
Time: 8:30 a.m. to 1:30 p.m.
Location: Eugene Unitarian Universalist Church
1685 W 13th Ave., Eugene, Ore.
For more information, call 208-850-6504