Thursday, Feb 02, 2023

S.E. Idaho growers brace for stripe rust pressure

Stripe rust has surfaced in SouthEast Idaho after a cool, damp, spring.

AMERICAN FALLS, Idaho — Cereal crop experts have discovered stripe rust infections in three areas of southeast Idaho and warn cool, wet weather could result in heavy disease pressure this season.

“Last year was a moderate year for stripe rust, but the susceptible varieties were hit hard,” said University of Idaho Extension cereals pathologist Juliet Marshall. “I suspect higher disease pressure this year.”

Marshall said the potentially devastating fungal disease, spread by orange and yellow airborne spores, has been widespread in Logan, Utah, with infections continuing north into Preston, Idaho.

Stripe rust has also been reported in the Seagull Bay area near American Falls Reservoir and in Arbon Valley.

“If it’s locally established very early in the season, there’s a higher chance of it exploding,” Marshall said. “Our (recent) cool, wet weather and cool nights are really good for stripe rust to continue to expand.”

In recent weeks, Marshall said stripe rust has spread into California, Oregon and Washington, and heavier spore loads could soon blow into Idaho.

Marshall said no stripe rust has been found yet in UI cereal variety trials in Aberdeen and Tetonia.

About a month ago, Chris Merrigan, a crop consultant with J.R. Simplot, Co., confirmed stripe rust in a field in the Seagull Bay area near American Falls Reservoir. Merrigan said between 10 and 20 percent of the irrigated field, planted in a resistant wheat variety, was infected.

However, Merrigan said the field was planted in wheat for consecutive seasons, elevating the infection risk, and he doesn’t believe a fungicidal seed treatment was used. Merrigan said spring grain growers still have time to mix fungicides with their herbicide sprays to prevent the spread of stripe rust, and he urges them to do so.

Lonnie Sparks, a crop consultant with CHS Bingham Cooperative, identified stripe rust in downy brome growing between two irrigated spring wheat fields in Arbon Valley. Based on the discovery, Sparks said the grower mixed fungicide with herbicide used on fall wheat fields planted in a susceptible variety, Brundage, and plans to spray fungicides on his spring wheat as well. Sparks also advised the grower to kill the weeds with a mixture of glyphosate herbicide and fungicide.

Marshall said she’s beginning to see cases of root rot in fall wheat fields that were heavily saturated with moisture, as well as pythium outbreaks in spring wheat. Pythium is a water mold that thrives when crops are planted in cool, wet soils, and can cause heavy damage to newly emerging crops with undeveloped root systems.

The good news, Marshall said, is that barley yellow dwarf virus doesn’t appear to be widespread in Idaho this year, as it has been during the past few seasons. Marshall said the virus, which is spread by aphids, has been confirmed in a few fall barley fields in the Murtaugh, Rupert and Burley areas. She believes growers have minimized the spread by delaying planting of fall crops until aphid migrations have passed and by using insecticidal seed treatments.

This story was originally printed by John O’Connell at the Captial Press: