Posted: Thursday, March 03, 2011 10:00 AM
Plant expert says infections remained viable over the winter
Plant pathologists advise Pacific Northwest wheat farmers to apply fungicide with their herbicide applications this year, the result of earlier-than-usual stripe rust sightings.
"I have a feeling it could be a really bad year," Oregon State University professor of plant pathology Chris Mundt said.
Mundt advised any farmers growing wheat varieties susceptible to the disease, such as Goetze or Tubbs, to apply fungicide with their herbicide even if there's no rust in their field.
"With wheat prices being as high as they are, my guess is they'll probably get their money back on that," he said.
Oregon State University associate professor Don Wysocki said rust infections from last fall were able to remain viable through the winter.
He advised growers to check their fields for rust. If they find rust this early and have a susceptible variety, they should consider the full-rate of fungicide with their spring herbicide.
"If you know you have it this early, it saves you some application costs," he said. "You don't have to do a separate operation putting that fungicide on."
Mundt estimated the majority of wheat acreage in the Willamette Valley is Tubbs and Goetze, and is potentially at risk.
High-temperature adult plant genetics providing resistance kick in when temperatures rise above a certain level and the plants being to reproduce. Last year, Goetze plants were hard hit before resistance could kick in, Mundt said.
New stripe rust strains moving across the globe in the last 10 years are more aggressive than older strains, Mundt said. Tubbs has a low level of high-temperature adult plant resistance, but was generally resistant enough to survive the older strains.
Not so with the newer strains, he said.
"Last year the rust just kept going and going and going," he said.
There are also concerns that previously resistant varieties may be at risk from the new strains, Mundt said.
"If you have a thousand more spores than you normally have, that's just going to increase the possibility," he said.
USDA Agricultural Research Service research plant pathologist Xianming Chen previously estimated it would be a "moderate" year for stripe rust. That position still holds, he told the Capital Press, although it may be an "upper level of moderate," with potential yield losses of about 40 percent. More than 50 percent is considered severe, Chen said.
Chen expected an updated forecast using February weather conditions the week of March 7.
In a notice to growers, Chen said rust develops quickly when the weather gets warm, with night temperatures in the 40s and day temperatures into the 50s.
Farmers should check their fields then. If they see stripe rust they should consider spraying with fungicide even before herbicide application, he said.
Growers must remain vigilant, Mundt said. There's a lag in time between the point the rust gets into the leaf and the point it is expressed, usually about two to three weeks. A grower who thinks he can live with 5 percent rust might have 30 percent rust a few weeks later.
"It's really critical growers and fieldmen get out there and scout the fields on a regular basis," Mundt said. "It's important every year, but especially this year."