A cold snap could kill the fungus but cause other problems

By MATTHEW WEAVER

Capital Press

Experts predict Northwest wheat producers won't see as much stripe rust as last year, but it will still be severe.

Yield losses could be approach 50 percent in highly susceptible wheat varieties, said Xianming Chen, plant pathologist for the USDA Agricultural Research Service in Pullman, Wash.

But compared to more than 90 percent losses seen in susceptible varieties last year, it will be an improvement, he said. Much of the region's wheat was infected last year.

"That does not mean a bunch of damage will occur on every cultivar," Chen said, noting most cultivars currently grown in the region have some level of resistance.

The stripe rust fungus, spread by wind, reduces yield, test weight and quality.

Stripe rust yield losses can be classified into four categories, with 0 to 20 percent being low, 21 to 40 percent being moderate, 41 to 60 percent being severe and 61 percent or higher being extremely severe.

In the last 40 years, stripe rust has caused an average of 35 percent yield loss in susceptible varieties, Chen said.

If the warmer winter weather continues, the rust will get an early start, Chen predicted. The weather will also affect the impact of stripe rust, he said. A colder January may result in less rust than predicted, while a cooler, wetter spring and summer would cause the rust to do more damage.

Mike Flowers, extension cereal specialist for Oregon State University, said he's already seeing stripe rust on his test plots.

Flowers expects to see fewer acres of susceptible varieties planted. He expects a lot of early-season fungicide applications, which is relatively inexpensive when applied in combination with herbicides.

Ideally, Flowers said, a cold snap would kill the fungus, but that could come with its own problems, such as winter injury of the wheat.

"It's kind of a double-edged sword," he said.

The prediction model covers most of the eastern Pacific Northwest, eastern Oregon and northern Idaho.

The western part of the region always has rust due to high moisture and higher temperatures during the winter.

Chen advised farmers in the western region to check their fields, but said they might wait to apply fungicide until the wheat is growing.