Experts say the likelihood of stripe rust outbreaks in the Northwest is severe, and they advise wheat farmers to monitor their fields.
USDA Agricultural Research Service research geneticist Xianming Chen upped his stripe rust forecast from moderate to severe after finding the wheat fungus in research plots in Walla Walla, Wash.
The relatively warm winter allowed stripe rust to survive, Chen said.
Chen said this year will not be as bad as 2011, when a warmer winter and heavy fall infections promoted the disease throughout the Northwest. Unusually early cold weather in November 2014 killed the rust in much of northern Washington, but the disease did survive in the southern portion of the state, he said. The fall infection was not heavy, he said.
This year may be similar to 2010, when rust started normally, but weather conditions in May and June were wet and cool, allowing rust to develop quickly.
The best conditions for rust are about 50 degrees Fahrenheit at night and 65-70 degrees during the day, Chen said.
“At this point, things are holding, but if we continue to have this type of warm weather, the pathogen’s going to like it,” Oregon State University Extension cereals specialist Mike Flowers said. “We’re just going to continue to have to fight it. It might be another tough year where we have to make multiple applications (of fungicide) in some areas to control rust.”
Flowers has received reports of rust in Sherman County.
Chen recommends farmers plant spring wheat varieties that are resistant to stripe rust, if possible. He acknowledged that farmers also consider other factors, such as yield and quality.
Winter wheat farmers should include a fungicide with a herbicide if they have a variety that’s susceptible to stripe rust or if they see rust in their fields, Chen said.
Tubbs 06, Xerpha and Clearfield 102 are moderately susceptible varieties, Chen said.
Flowers hopes farmers continue to plant more resistant varieties, noting the OSU variety Bobtail has strong resistance.
He recommends growers scout their fields and speak with neighbors to find out what’s happening.
“If rust starts to show up and you’ve got susceptible varieties, that’s when you need to be particularly attentive and get prepared to make fungicide applications,” he said. “When it pops up, you need to pull the trigger and make an application.”