Eastern Pacific Northwest wheat farmers who planted winter wheat varieties that are moderately susceptible or susceptible to stripe rust should apply fungicide, USDA stripe rust expert Xianming Chen says.

That’s about 20% of the overall winter wheat crop, Chen said. 

Even if farmers don’t see rust for those varieties yet, they should spray, he said.

Stripe rust started relatively late compared to last year, but could develop into an epidemic, considering high moisture so far and favorable weather conditions predicted in the next few weeks, Chen said.

For other varieties, farmers who see active rust or rust severity at 5% should apply fungicides as soon as possible.

Chen recommends farmers plant resistant or moderately resistant spring wheat varieties.

Looking for rust

Chen’s team of researchers recently checked fields across Washington state. They found stripe rust in experimental fields and nurseries, but not in commercial fields.

“So far, not yet,” Chen said.

Stripe rust likely died off in a Lincoln County, Wash., field where it was spotted last November, but could develop later on, he said. 

Winter crop nurseries in Lind and Central Ferry had more rust than the same time last year.

A nursery in Walla Walla has not reached the same degree of rust as last year.

Stripe rust has not yet been found in the Palouse area.

Nationwide, stripe rust has been reported in Oregon, Washington, Louisiana, Texas and Georgia.

Keep an eye on Piranha

Most susceptible varieties represent relatively small acreages, Chen said.

In recent years, Chen recommended farmers not plant UI Magic, and now that variety is “generally gone,” he said. 

Washington State University’s soft white wheat Clearfield variety Piranha CL+ is considered moderate. In some fields it has very good resistance, but in some Franklin County fields proved susceptible. That’s because of different races of stripe rust, Chen said.

For Piranha and other varieties, farmers should check their fields, Chen said.

“If they see rust, they should spray,” he said. “If not, they should not spray .. If they can wait a little bit, they maybe only (need to) spray one time.”

Varieties to watch

Moderately susceptible: AP700 CL, AP Legacy, ARS Crescent, Canvas, CPX66251, Curiosity CL+, Devote, Irv, Keldin, LCS Fusion AX, Milestone, Scorpio, TMC M-Pire, UI Palouse CL+, WB1532

Susceptible: Battle AX, Brawl CL Plus, CP7010, CP7909, Kivari AX, LCS Dagger AX, Snowmass 2.0, UI Magic

CL+, VI Voodoo CL+, WB4303, WB4394, WB Rimrock, Whistler, XF4303