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Lack of psyllids stymie insecticide research

Sean Ellis

Capital Press

There have been few potato psyllids spotted in eastern Oregon this year, which is making it difficult for Oregon State University researchers to report results of a field trial designed to find the best pesticide treatments for controlling the insects, which can spread the zebra chip disease in potato fields.

ONTARIO, Ore. — Oregon State University researchers in Ontario have had a difficult time reporting results from a first-year trial designed to find the most effective insecticide treatments for controlling potato psyllids.

The reason? Very few psyllids have been found in the area this season.

“I wish we had some results to share with you, but … it’s hard to show any treatment results when they’re all at zero,” Stuart Reitz, a cropping systems extension agent, told growers July 9 during a field day at OSU’s Malheur County experiment station.

Psyllids can spread the zebra chip disease, which causes dark stripes to appear in the flesh of infected spuds.

While psyllid pressure was heavy in the area last year, it’s been extremely low this year, Reitz said.

“Psyllid pressure has been relatively low, which is a good thing, except when you’re trying to do research,” he said.

Reitz said researchers aren’t sure why psyllid numbers have been so low this year, but it’s a good problem to have for growers.

“It’s a little bit of a mystery where they went and hopefully they’ll stay away,” he said.

The Malheur County trial is one of several being conducted in Oregon, Washington and Idaho to try to find the best way to control the insects.

“Each of us has a very similar set-up and we’re testing the exact same treatments,” said Eric Wenninger, assistant professor of entomology at University of Idaho’s Kimberly Research and Extension Center in southcentral Idaho.

Researchers in Washington and Idaho reported a similar situation to that in Ontario but they also expect to see that change later in the season.

“We’ve kind of got the same story,” said Tim Waters, a Washington State University extension vegetable specialist in Pasco. “We have to have good, consistent insect pressure to know the results are meaningful and right now it’s too early to tell.”

Though psyllid pressure has also been low in that area, researchers in Pasco started seeing numbers increase last week and plan to start spraying trials this week, he added.

“I think we’re going to have enough psyllids to do something this year,” Waters said.

It’s a similar story at UI’s Kimberly research center, but Wenninger said psyllid numbers have started out low and gradually increased throughout the season the past three years.

Psyllids haven’t shown up at the Kimberly research station yet this year, Wenninger said, but researchers expect them to later in the season.

“We’ll keep monitoring for psyllids and start our foliar sprays once they show up,” he said. “I’d be surprised if we see zero psyllids at the station this year.”



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