An average of 40 flies were caught during a sweep of 36 feet of hedgerow in a few minutes.
Based on the results, Bolda says baits will continue to be an important sentinel to detect initial infestations. But sweep netting will provide a better assessment of already established populations in caneberries.
Adopting other fruit-fly-control measures
When growers first began reporting damage, control methods remained an unanswered question. Pest control experts hoped that what worked on other fruit flies, such as husk fly and the Mediterranean fruit fly, would work on the spotted wing.
GF-120, which is a mixture of a bait syrup attractant and an organic form of the insecticide spinosad from Dow AgroSciences, is registered for fruit flies.
It is typically applied at 20 ounces of product in 1 gallon of water per acre. Many growers found success with applying GF-120 two times per week during the critical cherry-ripening period.
“Generally, we found that GF-120 on other fruit flies worked well in low to moderate populations,” he says. “In some orchards in Santa Clara County, I think the populations were just too high.”
Under high populations, there are so many flies that the bait is consumed before others have an opportunity to feed on it, he says.
A possible option could be mixing either malathion with Nulure or mixing Entrust, an organic spinosad, with molasses. Growers would then apply the mixture at a higher active ingredient rate and with more water volume, such as 5 to 10 gallons, per acre, Coates says.
For more information about the spotted wing drosophila, visit http://www.ipm.ucdavis.edu/EXOTIC/drosophila.html.
Contact Vicky Boyd at firstname.lastname@example.org or (209) 571-0414.