Published online: Jun 26, 2012 Insecticide, Fungicide
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Researchers recommend potato growers in the Pacific Northwest intensify their field scouting programs for the potato psyllids that spread the crop disease zebra chip.

Though no psyllids have yet been found in Idaho fields, the insects have surfaced on greenhouse-grown plants in garden centers in Twin Falls and Boise, according to an update posted by the Treasure Valley and Pacific Northwest Pest Alert Network. A single potato psyllid was found in one field in Irrigon, Ore., on June 11, and another field in Hermiston, Ore., on June 13.

No psyllids have yet been found that are positive for the liberibacter bacterium that causes zebra chip, which leaves bands in tuber flesh that darken when fried and reduces yields.

Oregon State University researchers have found volunteer potato plants in fields that were hard hit by zebra chip last season that are positive for Liberibacter. The alert suggests that growers closely monitor volunteers and submit symptomatic plants for analysis.

"There likely isn't a lot of risk yet because there are so few psyllids so far and they're testing negative for the pathogen that causes zebra chip, but we don't know enough to know for sure," said Andy Jensen, an entomologist who researches for the Washington, Oregon and Idaho potato commissions.

Jensen anticipates large numbers of psyllids won't show up to colonize potato fields until mid-July.

"The sense I'm getting is most people have insecticide programs in place and their plans are well developed. That will severely limit the development of the disease for the most part," Jensen said. "It comes at a great expense. Limiting damage means an expensive insecticide program."

Zebra chip first arrived in the Pacific Northwest last season. In Texas, where zebra chip has been a problem for several years, Jensen said growers have developed effective management programs. Nonetheless, they still suffer some losses to zebra chip.

SOURCE: John O'Connell, Capital Press