Cold weather may help farmers battle destructive bugs
Capital Press
Your frozen fingertips may not appreciate it, but the extended cold snap gripping the Pacific Northwest through the first week of January may actually do some good.
Oregon pest specialists say it could reduce the population or at least delay the onslaught of spotted wing drosophila, or SWD, the fruit fly that can cause devastating damage to raspberries, blackberries, blueberries and other small fruit crops.
“We’re very optimistic that it will definitely impact SWD and kill off a fair amount,” said Tom Peerbolt, founder and senior consultant with Peerbolt Crop Management. “From that viewpoint it’s a very good event. We’re killing a bunch of them off and that’s good.”
Peerbolt said SWD almost exclusively over-winter as adult flies, making them susceptible to cold. While they can take refuge, an extended run of cold temperatures can knock down their numbers, he said. The flies can go through a dozen breeding cycles per year, and the cold may stall the population buildups that lead to heavy damage, Peerbolt said. Even gaining a week or 10 days would help mid-season harvests, he said.
Peerbolt said SWD love caneberries, and growers are planting fewer late-season varieties in an attempt to avoid some damage. SWD populations build over the summer, so the earlier farmers can harvest, the better.
Jim Labonte, an entomologist with the Oregon Department of Agriculture, said planting earlier berry varieties is a “really good strategy” in the fight against spotted wing drosophila. “I’m glad to hear that,” he said. “Toward the end of the year, the population gets to be tremendous. I think that would help.”
Otherwise, Labonte said he’s not sure the recent cold Oregon weather will have much effect on SWD or another major pest, the brown marmorated stink bug, which damage hazelnuts and feed on a wide variety of other crops.
Both of them live in regions of the U.S. that are far colder than the Willamette Valley, he said. “I’m uncertain of the threshold of severe cold that’s sufficient to really knock them down,” he said.
“Even if it does, both of these things can reproduce very efficiently,” he said. “They may have a slow start in spring, but by mid-season there will be plenty of them around.”
He said stink bugs produce far fewer generations of offspring per season than SWD, but are “remarkably tough creatures” and very good at sheltering themselves from the cold.
Spotted wing drosophila are native to Asia but arrived on the West Coast about 2008. They are unusual fruit flies in that they attack ripe or ripening berries and fruit; most flies are attracted to over-ripe or rotting produce. The female SWD has a serrated-edged ovipositor that it uses to cut through the berry surface and lay eggs inside. The developing larvae feed on the fruit from the inside, turning it into a gooey mess that cannot be used commercially.
Common pesticides work against them, but require additional sprayings and cost to growers. In addition, prolonged pesticide use may lead to the flies developing resistance to it, Peerbolt said.