Farmers Act Quickly, Save Potatoes From Late Blight Fungus Threatened To Wipe Out Harvest In Southern Idaho Fields

Farm experts say with careful harvesting, spores from the potato disease late blight can be managed.

The disease threatens most of southern Idaho’s potato industry. It was spotted the first week in August in Fremont County and quickly spread to Madison County.

Although it’s expensive, local farmers have wasted no time making aerial applications of fungicides.

“Our farmers here are probably some of the best,” said County Agent Gale Harding. “They got right on it and in five to seven days got it under control.”

It’s expensive.

Harding said it costs $15-20 per acre for an application of fungicide. A farmer with 450 acres will pay about $9,000 per application. If they spray seven times before harvest, that’s $63,000.

Farmers who have detected signs of late blight, including lesions on leaves and stems, are advised to spray aggressively and in some cases to kill the vines to prevent spread of the diseases.

Even in fields with no signs of late blight, farmers are being urged to spray as a preventive measure, Harding said.

Bill Bohl, University of Idaho extension educator and potato specialist, said he has been recommending that potato vines be completely dead before harvest.

“All above-the-ground growth needs to be dead three weeks before digging,” he said. “When you kill the green growth, you kill the fungus.”

Potatoes need to be absolutely dry when put into storage and careful harvesting should prevent breaks in potato skins because the spores survive on moist surfaces.

Farmers appear to be on schedule with killing potato vines, Bohl said.

Vines are killed several weeks before harvesting to allow the potato skins to be more durable and protect spuds during harvest.

Dennis Leavitt farms in Moreland and Groveland. He said he is following chemical and fertilizer recommendations on handling blight spores.