Fruit fly population explosion frets Willamette Valley growers

Invasive pest can lay eggs in fruit before it softens



McMINNVILLE, Ore. — For berry and stone fruit farmers, nature has conspired to create perfect conditions for an explosion of a crop-damaging fruit fly known formally as drosophila suzukii and informally as the spotted wing drosophila.

Researchers at Oregon State University are predicting record levels of the invasive pest, which wreaks havoc on blueberries, raspberries, blackberries, strawberries, cherries, peaches, prunes and other popular fruits. “The climate is absolutely perfect in many ways, at this stage,” said horticultural entomologist Vaughn Walton.

Numbers swelled last year throughout the Willamette Valley, and a mild winter ensures an unusually high survival rate, Walton said. Adding to the threat, “Now, we’re going into this abnormally warm spring period,” he said.

He said, “It doesn’t necessarily mean growers will lose money for their crops.” But he said it suggests they will have to spend more to maintain control.

“Everybody is on alert,” said Extension Service horticulturist Jeff Olsen. “It’s an invasive pest. It’s an issue throughout the Willamette Valley, and Yamhill County is part of that.

“They’re in the orchard areas. Cherries are the most affected.”

What makes this fly different from others, Olsen said, is a serrated oviposit allowing females to saw into fruit to lay their eggs. It doesn’t require soft, overripe fruit in order to give its eggs a ready-made food supply, he said.

“At this stage, the only option we have is pesticide applications,” Walton said.