Zebra chip disease attacking potatoes throughout the West has been found in the Columbia Basin, and growers in Washington, Oregon and Idaho are alerted to be on the lookout for more outbreaks.
First reported in the West – including Colorado, Nevada and Wyoming – just six months ago, the malady capable of causing millions of dollars in crop losses is a "serious disease," says Joseph Munyaneza (cq), a U.S. Department of Agriculture Agricultural Research Service entomologist in Wapato, Wash.
The potato psyllid which vectors the disease "does occur in Washington and Oregon," he says, "despite some scientific literature which says this pest is not found in the Pacific Northwest. We have trapped them and their presence here is confirmed."
The vector was found in high numbers in July, September and August in the Yakima Valley and near Prosser, Wash., he reports.
"You begin to find them in late June and early July in this region ."
Although the pests may be found in some areas, it does not always mean zebra chip disorder is also found on potatoes in the same vicinity, he notes. Most finds in the Columbia Basin have been near the Columbia River.
"We know that the psylla are migrating and reproducing in this area," adds Munyaneza.
But since zebra chip is a new disease, not much is known about it, he says. But researchers have discovered that just one infected psylla per plant can cause zebra chip to occur within hours. Tuber development will stop in stricken plants.
"It takes about three weeks for tuber symptoms to show up after the plant has become infected, and this can occur even before above ground symptoms are visible," he says.
There are no known resistant potato varieties against this disease, Munyaneza notes.
When monitoring for the psyllid, use of yellow sticky cards has not proven to be highly successful, he says, advising growers to pick suspected pests from leaves and examine them using a magnifying ring. For more on how to identify these pests, go to http://zebrachip.tamu.edu.
In Texas, where the disease level is high, tests show that early season foliar sprays may be helpful. No pesticide tests against the vector have been launched in the PNW, but it is known that control of the pests must occur at all life stages, says Munyaneza, who has been working on the disease under a grant from Frito-Lay.
Texas A&M University is working on a comprehensive study to find the best management techniques to fight the psyllid. At this time, the best advice researchers provide is to target the vector with insecticides at planting (seed treatments) and by soil drenching, as well as foliar applications during the cropping season.
University researchers in Texas remind growers that rotation of pesticide chemistries is important, as is the effort to target the pests are their proper growth stage.
For more on this story, see the February issue of Western Farmer-Stockman.