Take proactive approach to zebra chip, potato psyllid management

08/20/2012 05:48:00 PM
Vicky Boyd

zebra chip in potatoesSilvia Rondon, Oregon State UniversityGrowers should approach zebra chip as they would any other potato disease, according to an Oregon State University Extension plant pathologist.Last year, zebra chip made headlines when the potato disease caught a couple of Columbia Basin growers off guard and devastated their crop.

This year, potato growers appear more aware of the problem and are taking steps to prevent similar occurrences, said Phil Hamm, an Oregon State University Extension plant pathologist and director of the Hermiston Agricultural Research and Extension Center.

And despite last year's bad news, he said growers should view zebra chip as just another disease they need to scout for and manage.

"It's another late blight or PVY or leafroll virus or whatever," he said. "Sure, it's a new disease and it can be very, very devastating, and we saw that devastation a year ago. But if growers do their due diligence and do what's required, it's just another disease they have to manage."

Hamm attributed last year's problem to growers being unaware of Liberibacter-positive psyllids.

"In the fields that were hardest hit, they had no insecticides on them for weeks and weeks and weeks," he said. "That's because there was nothing to treat for."

Or growers thought at the time.

The industry has since learned.

Hamm said he knew of about a half dozen potato fields in the Columbia Basin this season where potato psyllids have tested positive for the Candidatus liberibacter, the bacterium responsible for zebra chip.

But there have been no "train wrecks," and growers are making the necessary insecticide applications to control potato psyllids and prevent them from reproducing.

"You can't prevent (psyllids) from coming in, but you don't let them colonize the fields," Hamm said.

Potato psyllids pick up the zebra chip bacterium from infected plants and then spread it to healthy plants.

The disease, which is harmless to humans, affects the way potato tubers store sugars.

When the potatoes are heated, such as during frying, the sugar caramelizes, causing brown stripes.

Citing research, Hamm said growers need to maintain psyllid control until the vines are killed to protect tubers.

"You don't want a late-season infection to come in," he said. "After the psyllid feeds on top of the plant, we don't know how long it takes for that bacterium to get down into the tuber."

Recent research has shown that zebra chip symptoms increase in storage, Hamm said.

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