WSU receives $2.7 million to research costly potato threat

By Scott Weybright, College of Agricultural, Human & Natural Resource Sciences

potato-80PULLMAN, Wash. – Zebra chip disease, caused by a bacterium carried by insects, can ruin a potato crop; but little is known about where it comes from and how it can be avoided.

Thanks to a nearly $2.7 million grant from the U.S. Department of Agriculture’s Specialty Crop Research Initiative, Washington State University researchers hope to find better ways to manage the potentially devastating pathogen.

A potato psyllid, left, is eaten by a predatory big-eyed bug.

“If a field is found to be infected, that can lead to rejection of an entire crop,” said Bill Snyder, a WSU entomology professor and co-lead on the grant. “Potatoes are expensive to grow, so an outbreak can cause millions of dollars in losses.

“Farmers often don’t know their field is infected until their potatoes go to the processor,” he said. “They may not find out until winter that their crop is worthless – just when they’re ready to get paid.”

Regional teamwork

Infected potatoes develop brown lines, like zebra stripes, that are most apparent when fried. The striped sections easily burn and caramelize, leaving a bitter flavor. Though there are no known health risks, the potatoes are unusable.

Zebra chip disease causes brown stripes that darken and turn bitter when fried, making the potatoes unusable in chips or fries.

Zebra chip is carried by potato psyllids, an otherwise harmless insect. Psyllids are found in increasing numbers in the Northwest, and zebra chip problems are becoming more common, Snyder said.

The research team hopes to decode the genetics of psyllids that carry zebra chip, figure out how the psyllids travel and eventually create predictive maps that growers can use to determine risk.

The team includes Snyder and entomology professor David Crowder, whose labs will study psyllid DNA and psyllid movement patterns; Gerrit Hoogenboom, director of WSU’s AgWeatherNet weather monitoring system; entomologists at the USDA laboratory in Yakima, Wash.; an agricultural economist from the College of Idaho; and extension scientists from Washington, Idaho and Oregon. The Potato Research Consortium, comprised of potato industry groups from the three states, will also participate.

“It’s a regional problem, and we need to look at the problem comprehensively,” Snyder said. “This is vitally important to maintain the potato industry in this region.”

Carried by wind or overwintering?

The host psyllids have several known genetic variations. Some psyllids survive northwestern winters, Snyder said, but others ride on winds and are blown into fields in the region seasonally.

Potato psyllids feeding on bittersweet nightshade, a weed that keeps psyllids alive through the winter.

His lab is tasked with figuring out if the blown-in variety, the local version or both carry the zebra chip bacterium.

“If it’s the blow-in version, there’s not much we can do about that,” he said. “We can’t control the wind.

“But we can monitor weather patterns to see where they’re coming from,” he said. “If the pathogen is carried by the winterized psyllids, then we have to find where they’re living in the cold weather… and how they’re surviving the winter.”

While it’s a five-year grant, the scientists hope to have solid answers and working, mobile-friendly, predictive maps in three years, Snyder said.

Relatively new arrival in Northwest

Zebra chip symptoms first showed up in Washington in 2011, after crippling the potato crop in states like Texas over a decade ago.

Already, zebra chip has cost the regional potato industry millions of dollars in lost crops and increasing management costs. Snyder hopes the work enabled by this grant will allow the regional potato industry to survive the zebra chip outbreak.

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Bill Snyder, WSU entomologist, 509-335-3724,