Devastating potato pest found in southern Idaho

TWIN FALLS, Idaho — Officials with the University of Idaho’s Kimberly Research and Extension Center say a disease that could devastate the state’s potato crop has been found in a Twin Falls County field.

Erik Wenninger, a professor with the extension center, said tests were positive for the bacterium that causes zebra chip. More tests are being done this week to confirm the results.

“It would be awfully surprising to have it come back negative,” Wenninger told The Times-News (, adding that officials are proceeding cautiously.

The potato disease causes flecking in potatoes’ flesh, and when they are fried, the chip darkens. The defect can make the potatoes undesirable for fresh and process potatoes.

Officials tested for zebra chip and other diseases by putting sticky cards in a commercial potato plot and then testing the insects that stuck to the card. The zebra chip bacterium was found on adult psyllids — a type of insect that feeds by sucking plant juices.

Wenninger posted a warning to farmers on Monday on the Pacific Northwest Pest Alert Network.

“I don’t want to get people panicked, but I also don’t want to withhold information,” he said.

Wenninger and his colleague, Nora Olsen, wrote in a report published by the Oregon State University Extension Service that the disease has the potential to be economically devastating.

Wenninger suggests that farmers intensify their monitoring programs for the disease. Once found, the disease can be fought using season-long, weekly applications of insecticides.

Psyllids have been in Idaho for decades, but Wenninger said it wasn’t until late in the 2011 growing season that the bacterium for zebra chip was found in low levels in Idaho, Oregon and Washington.

“If concentrations are heavy enough, you can definitely see damage during the (growing) season on the above-ground portion of the plants,” he said.

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