Wet spring in Idaho raises risk of late blight

An unusually wet spring has raised the threat of late blight in Idaho's potato crop, according to experts.

The disease had not been reported as of Tuesday, June 30, but there is an increased chance that it could before the growing season is over.

Cool, wet conditions favor the development of late blight. The presence of the disease in 2008 also increases the risk to this year's crop.

Late blight was found in some fields in south-central Idaho last year, and it's possible that the pathogen may have survived on infected tubers that overwintered, said Phillip Wharton, a University of Idaho potato pathologist based at Aberdeen.

Spores can be spread from infected plants in one field to healthy plants in surrounding fields by wind, splashed rain, animals or mechanical transport.

Cull piles and infected seed pieces are also potential disease sources.

If the pathogen was present this spring from any of those sources, it would have had near-ideal conditions to spread, experts said.

The threat is greatest in areas where potato rows have already closed to form a canopy, Wharton said.

"Right now there is a very high risk of infection,"Wharton said Monday, June 29.

Spud growers should apply some type of protective fungicide to guard against the disease, he said.

"Growers need to get hold of their crop consultants and make sure they have a good spray regime in place for the year,"Wharton said. "I really think they need to be a bit more proactive this year in getting the sprays on sooner rather than later."