Printed on: September 15, 2013

Late blight fungus contained

By NATE SUNDERLAND
nsunderland@postregister.com

BLACKFOOT -- A case of late blight fungus discovered in a Bingham County potato field has been contained, state agronomists said. of late blight fungus discovered in a Bingham County potato field has been contained, state agronomists said.

The relatively rare disease was found in late August. The grower quickly sprayed the field to eliminate the pathogen, said Wayne Jones, University of Idaho Bonneville County Extension educator.

Late blight is a devastating disease with the potential to wipe out large fields of tubers within 10 days of first infection unless treated with a chemical fungicide.

Characterized by dark, yellow-ringed lesions on potato leaves, it is rare in eastern Idaho. Before the August discovery, the last reported case was at least five years ago, Extension officers said.

"As soon as we know late blight is in the area, we start spraying, because if it shows up, it can destroy entire fields," Jones said.

Late blight isn't the only fungus worrying potato growers, however.

Eastern Idaho agronomists also have observed a marked increase of verticillium wilt in the majority of eastern Idaho potato fields. Verticillium is a common fungus that eastern Idaho spud farmers have battled yearly for the past century, Jones said.

The fungus, which turns healthy potato leaves brown, can live for years on dead organic material in the soil. It becomes a major problem when a farmer grows potatoes in the same infected field year after year.

"It can carry over to the next year ... and untreated, you can easily lose 50 percent of your yield," Jones said.

Verticillium is more prevalent this year because potato plants are more mature due to the long, hot and dry summer. The disease has a greater effect on older plants.

Farmers combat verticillium with fumigation, by using green manure and by rotating crops.

"Despite the increase ... most fields are healthy," Jones said. "Most farmers recognize they'll have this issue so they do something about it, because if they don't, they'll go broke."