KENNEWICK, Wash. — Zebra chip control costs Northwest growers nearly $11 million a year in treatment products and application expenses, a researcher says.
Gina Greenway, a business and accounting assistant professor at the College of Idaho, is also working to quantify zebra chip’s effects on potato quality and developing a cost-benefit analysis of different insecticide spray regimes.
“Incremental reductions in spray applications can have a significant impact,” she said.
Depending on environmental conditions, the variety of tools provided by the research will give growers the ability to make informed decisions when and if an application is necessary, she said. That has the potential to significantly reduce the cost of controlling the psyllids that spread zebra chip, Greenway said.
“It’s just such an expensive problem,” she said during the Washington-Oregon Potato Conference in Kennewick, Wash.
Zebra chip is a bacteria vectored by potato psyllids. It causes a striped discoloration in potatoes that becomes more pronounced when the potato is cooked.
Psyllid numbers in fields are usually low early in the spring and gradually increase, peaking late in the season most years, said Erik Wenninger, associate entomology professor at the University of Idaho in Kimberly.
“A lot of individual fields might see virtually no psyllids for the whole season, and then shortly before harvest, we start seeing psyllids show up in the fields,” Winninger said. “The question is, ‘Do I need to worry about zebra chip in this field?’ Can you get away without spraying right at the end of the season?”
After conducting greenhouse testing, Wenninger said the risk of zebra chip is “quite high” at the time of harvest or after time in storage if infection occurs four or more weeks before vinekill.
Zebra chip is highly likely to develop in storage if the infection occurs three weeks before vinekill. The disease has a low to moderate chance of developing in storage if the infection occurs two weeks before vinekill. The risk is low for both harvest and storage one week before vinekill, Wenninger said. There is a low to moderate risk if infection occurs at harvest.
Wenninger will next conduct similar greenhouse tests for different potato varieties, and study how quickly zebra chip develops during storage.