Capital Press

A mild fall has provided ideal conditions for winter wheat crops to take hold throughout Idaho, according to the U.S. Department of Agriculture.

Cereal pathologist Juliet Marshall, however, warns growers that the temperate weather is also perfect for a repeat of a stripe rust outbreak that decimated many winter wheat fields planted last season.

Marshall, with the University of Idaho Extension, confirmed stripe rust infestations Oct. 26 in volunteer wheat near Declo and the Neeley area by American Falls.

As of the week ending Oct. 23, the National Agricultural Statistics Service reported 98 percent of Idaho's winter wheat had been planted and 65 percent had emerged.

"The winter wheat is really well established this year, I think," said Rockland dry farmer James Robinson, who planted on Sept. 15.

Adam Permann and his father Ivan, who farm dry land between American Falls and Rockland, planted 1,800 acres of winter wheat in early September. Adam said the fields already "look like a lawn."

"We have good moisture here lately," Adam said. "There's a lot of things that can happen, but so far it looks good -- as long as we don't get rust again."

During the July harvest, stripe rust took a heavy toll on the Permanns' soft white winter wheat, Brundage. Even after they sprayed fungicides, their yields were down by about 10 bushels.

"By the time you see it, it's almost too late," Adam said.

In their recent planting, Ivan explained they abandoned the Brundage and planted more stripe rust-resistant varieties.

The Permanns will also heed advice Marshall offered Tuesday night while speaking at the Power County Grain Growers meeting. She urged growers to destroy any volunteer growth following winter wheat harvest to avert the "green bridge" effect -- a host crop carrying stripe rust into winter wheat planting.

Marshall said multiple factors have aligned lately to heighten the risk of another outbreak.

"There's a lot of green bridge material out there," Marshall said, advising growers to kill it.

She's also concerned that growers continue planting susceptible varieties. Climatologists predict another La Niña year will result in increased winter precipitation. Like last year, Idaho is entering winter with thawed ground, and snow could insulate stripe rust until spring.

Marshall had never seen stripe rust surface during an Idaho fall before last year, when it was discovered in an Aberdeen test plot. Validating her fears that the rust had overwintered, she found it again in that plot after the snowmelt.

She's seen yields decrease by 70 percent in Brundage fields.

"Massive spore clouds picked up by wind as far west as Oregon and Washington can be deposited in a rain event here," Marshall said.

She advised growers to check their fields for signs of stripe rust in the spring and to mix a full rate of fungicides into their herbicides if they detect it.

Fight stripe rust

Cereal pathologist Juliet Marshall suggests these steps for avoiding stripe rust:

• Destroy volunteer wheat that is growing under grain.

• Plant late.

• Plant resistant varieties.

• Use seed treatments including Baytan30 at 1.25 fl. oz./100 pounds of seed and Dividend XL RTA at 10 fl. oz./100 pounds of seed.

• Scout for fall infections and mark infected areas with flags or GPS coordinates. Examine older leaves for living lesions.

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