Experts warn of diseases spreading in fields across state

By DAVE WILKINS
Capital Press

Cool, wet weather this spring provided the perfect breeding ground for fungal plant disease in Idaho and the arrival of warmer weather is no time to stop scouting fields, crop experts warn.

Juliet Windes, a small grains plant pathologist with the University of Idaho Extension, said she's seeing an unusual amount of pythium root rot in both wheat and barley this year.

It's not unusual to find pythium root rot in spring barley because the crop is planted in some of Idaho's coldest, wettest environments.

This year the disease has even hit winter and spring wheat.

"It's surprising to see how prevalent it's been this year," Windes said in an interview. "The weather has been tremendously conducive for pythium and other soil-borne fungi."

Cool, wet weather is also conducive to the development of powdery and downey mildew, white mold, stripe rust, early blight and late blight.

Stripe rust has been widespread in wheat fields in Washington state this year, but so far hasn't been significant in Idaho.

A small amount of stripe rust has been reported in southwest Idaho wheat fields, and in one hard red winter wheat field near Burley.

Most winter wheat fields are probably past the danger point, but spring wheat is still vulnerable, Windes said.

"Now's the time to look at the spring wheat," she said. "It's getting warmer and drier, but we're still not out of the woods by any means when it comes to stripe rust."

Growers should check with their crop consultant to determine whether any disease outbreaks are significant enough to warrant fungicide treatments.

Diseases that wouldn't require fungicide treatments during a normal year may warrant treatments this year, Windes said. One example is barley scald, a foliar fungal disease that has developed further this year because of cool, wet weather.

Crop experts are advising growers to apply protective fungicides to sugar beets to guard against powdery mildew and to potatoes to guard against late blight.

There were no reports of late blight in Idaho as of June 28, but crop experts said it's likely to occur sometime during the growing season given the presence of the disease last year and recent cool, wet weather.

"It wouldn't surprise me at all," Phil Nolte, a UI seed potato specialist, said in an interview.

Cool, wet weather, while conducive to late blight, has also delayed development of the crop. In Eastern Idaho, many fields are still weeks away from row closure. The risk of late blight increases once potato rows have closed, forming a foliar canopy.

"I think what is working in our favor is that the crop is so far behind in its development," Nolte said.

Several areas in Idaho were hard hit with late blight in 1997 when frequent afternoon rain showers occurred during the growing season.

Nolte sees some similarities with this growing season.

"There is a lot of moisture in the system," he said. "The stage is set for something to happen."

The earliest report of late blight in Idaho was on July 5, 1995, the first confirmed outbreak of the disease in Idaho in the modern era.