A “very cold” February dropped expected stripe rust levels from severe to low.

Highly susceptible wheat varieties are now expected to only have an 18% yield loss due to stripe rust, down from a 41% prediction made in January.

“Usually, the coldest (temperature) is in late December or early January, but this year, we had quite a warm winter until February,” said Xianming Chen, USDA Agricultural Research Service research plant pathologist.

Fungicide application is not recommended for winter wheat fields unless stripe rust is observed during the crop season.

For spring wheat and barley, Chen recommends planting resistant and moderately resistant varieties.

In an average year, about half of Washington’s wheat acreage requires fungicide.

Chen made a similarly low forecast in 2021. That year was a 30-year low due to dry conditions, to the point where Chen had to inoculate research fields just to get some stripe rust to develop for research purposes.

He’s planning to inoculate a research field in Pullman, Wash., this year.

“Now we can be quite sure it will start very late,” he said.

A later fungicide application is possible, depending on when the rust starts, Chen said.

Growers should still be checking their fields, he said.

Never rust-free

Fields covered with sufficient levels of snow, about 2 to 3 inches, would have protected some stripe rust, he said.

“We’ve never had a year that is completely rust-free, we always have some,” he said.

Particularly in western Washington: “Rust should still be in Mount Vernon. That area always has rust.”

Stripe rust has not been found in central Washington, Chen noted in his forecast. He and a colleague checked wheat fields in Whitman, Adams, Lincoln, Franklin and Walla Walla counties, and reported the wheat was generally in good condition without obvious winter injury.

No stripe rust was observed in any of the checked fields, including the commercial wheat field east of Almira along Highway 2, a field where Chen found stripe rust in November 2024.

Last year, stripe rust was found in several fields by the end of February, Chen said.

Not reported anywhere in the country

With the low winter survival, stripe rust is likely to enter eastern Washington wheat fields later from outside of the region, Chen said. The Cascade Mountains block most rust from western Washington, but it can still come from western and southern Oregon and California.

So far, stripe rust has not been reported anywhere in the country, Chen said. By this time last year, stripe rust had already been reported in Washington, Texas and Louisiana.