Scientists are looking at several unique methods for controlling spotted wing drosophila in blueberries.
“But that is not going to help you this year,” Oregon State University entomologist Vaughn Walton said. “At this stage, the most effective way to deal with spotted wing is using insecticides.”
In a year where cool weather has persisted for much of the summer, spotted wing drosophila numbers have exploded, affecting both early- and late-season cultivars and forcing growers to aggressively treat berries to avoid damage.
Walton said 2019 is one of the worst years for spotted wing drosophila since the pest first showed up in commercial fruit production in Oregon nine years ago. In a matter of one week, he said, fruit infestation levels in blueberry trials at OSU’s Lewis-Brown Research Farm in Corvallis went from approximately 1% to 60%.
“This is really a serious problem,” he told growers at a field day last month. “Don’t take any chances. Do everything in your power to make sure it is under control. You don’t want to be in the scenario that we are in where we are losing the majority of our fruit.”
Walton said it is also is important that growers use spray equipment that provides thorough coverage.
“What you need to do this year is make sure that you use equipment that gives you thorough coverage throughout the canopy,” he said. He added that higher registered rates of active ingredients can improve management efforts.
“You want to get the active ingredient into the center of the bush. You want to make sure that you are taking those populations out of the center of the bush,” he said.
Using compounds that control more than just the adult stage of the pest also can provide benefits, he said.
“There are some really good compounds that kill the immature life stages, as well as the adult stage,” he said. “You can actually kill larvae in fruit if you are using the right compounds.
“As soon as your crop ripens, if you use your more effective compound, it is going to give you a longer-term effect,” he said.
Looking ahead, Walton advised growers to stay tuned for information on SWD control technologies that are showing promise, including a product that increases the skin integrity of blueberries, which makes it harder for spotted wing drosophila to penetrate and lay eggs inside the berries with their ovipositor, and a disruptor that has been shown to significantly reduce crop damage.
Both methods can be effective at helping control spotted wing drosophila, he said. But in a year like this, thorough coverage with an effective insecticide may be the best bet.