By JOHN O'CONNELL
It appears the tiny winged insects that can spread the crop disease zebra chip in potato fields will overwinter in Boise, Idaho, this season, despite the city experiencing one of its coldest Januaries on record.
Zebra chip, which creates bands in tuber flesh that darken when fried, first arrived in the Pacific Northwest in 2011. It's caused by the Liberibacter bacterium, which can be harbored by aphid-like potato psyllids that tend to migrate to the region from the south during summer.
Andy Jensen, regional research director for the Idaho, Washington and Oregon potato commissions, found overwintering psyllids in Boise last season, but speculated a mild winter may have aided in their survival.
According to the National Weather Service, Boise started this year with the 10th coldest January since the 1860s, when weather records were first kept. For the month, the average temperature was 19.6 degrees, 11.7 degrees below normal.
Nonetheless, Jensen, an entomologist, had little trouble finding living psyllids when he searched the Boise area in early February, and again this month.
"It's a little surprising to me how well they came through," Jensen said.
No overwintering psyllids have yet been found near Twin Falls or east. Jensen hopes to soon research psyllid biotypes to determine which ones overwinter and which ones cause crop problems.
On March 12, researchers with the Pacific Northwest and Treasure Valley Pest Alert Network, run by the University of Idaho, posted an alert indicating the first evidence of zebra chip in eastern Idaho. It confirmed potato samples recently submitted for testing from Power County were positive for the Liberibacter bacterium.
"It's unsettling to say the least that they found it (in Power County) because that shows it's there, and that's what we've been afraid of," said Dan Hargraves executive director of Southern Idaho Potato Cooperative. "It's a major area for the guys I represent."
Jeff Miller, who aids in testing samples for zebra chip with Rupert-based Miller Research, emphasized the test found just a trace amount of infection.
"The surprising thing to me was that we hadn't seen it in eastern Idaho until just now," Miller said.
Miller takes the finding as further evidence that U of I should broaden its psyllid monitoring program this season. He'd also like to see larger untreated test strips next season in experimental test plots to provide a better comparison with insecticide-treated plots.
"I think we'll see a lot more monitoring both through U of I and I've heard private consultants will be monitoring more to see when adult psyllids are coming in," Miller said.
Power County potato grower Klaren Koompin said his crop consultant intends to step up psyllid monitoring on his fields this season, especially near the Snake River and American Falls Reservoir, where psyllids may survive on vegetation along banks.
If psyllids are detected, he'll likely step up his spraying program. If not, he may spray even less than last season.
"We'll just have to wait and see what the year brings," Koompin said.