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Extension agents sound alarm about blight threat

Published on May 26, 2011 3:01AM

Last changed on June 23, 2011 7:18AM

Wetter-than-normal conditions set stage for late blight woes


Capital Press

It's not too early to worry about late blight, according to potato experts.

The disease was detected last year in several potato seed growing regions across North America, increasing the risk that commercial growers could unknowingly plant infected spuds this year.

The likelihood that the fungal disease is already present, coupled with cool, wet weather that's conducive to its spread, could be a recipe for an outbreak, said Phil Nolte, a University of Idaho Extension seed potato specialist in Idaho Falls.

Late blight was found in several potato production areas last year, including some in the Midwest that have a history of exporting seed, Nolte said.

"The likelihood that someone could import infected seed is high," he said.

More than 150 years since the Great Potato Famine ravaged Ireland, late blight is still a serious potato disease worldwide. Modern pesticides and plant science have helped.

One of the first lines of defense is fungicide treatment.

Nolte recommends that growers apply a protective fungicide a week to 10 days before row closure and then another about 10 days later.

"Two applications early is probably the minimum to ensure that you don't have a problem later," he said.

Spraying before row closure gets fungicide to the underside of plant leaves, Nolte said.

Late blight tends to be less of a problem in Idaho because of the state's hot, dry climate. But the weather this spring has been cool and wet -- ideal for the spread of late blight spores.

"Currently we are in a wetter-than-normal weather pattern. If it persists for any length of time, we could have a real problem this year," Nolte said.

Idaho had its first serious brush with late blight in 1997. It was a year of heavy snowpack, high runoff and cool, wet weather throughout much of the early growing season.

"We are looking at exactly the same kind of weather pattern," he said.

There have been no outbreaks of the disease yet in the Northwest, but it's still early in the growing season.

Growers should scout their fields, especially if they've imported seed from outside the region, Nolte said.

For the latest on plant disease threats and outbreaks throughout the Northwest, growers can visit www.pnwpestalert.net.


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