Posted: Thursday, May 26, 2011 10:00 AM
Photo courtesy of Mike Flowers/Oregon State University
Stripe rust appears on a leaf at the Pendleton, Ore., Oregon State University wheat breeding nursery.
Growers in Oregon may have to use a rare third fungicide application
Even though there's more stripe rust in Pacific Northwest wheat fields this year, researchers say the outlook is good -- as long as farmers spray their fields and keep an eye on them.
Mike Flowers, extension cereals specialist at Oregon State University in Corvallis, Ore., said most farmers have done a good job of scouting their fields and spraying as needed. He expects close to 5 percent loss in yields statewide.
"You have to balance that with the fact we've had an extremely good crop year," he said. Flowers estimated 70 percent of the Oregon crop has been affected by stripe rust.
Flowers said the appearance of stripe rust in areas where the disease doesn't normally occur is of particular concern.
"Areas where we do not see stripe rust, period, are seeing multiple fungicide sprays," he said. "It's really hard to find a field that doesn't have stripe rust in it."
Fall infections simmered and began to affect susceptible varieties like Tubbs 06 and Xerpha, Flowers said. With a cool, wet spring following a relatively mild winter, the disease is exploding, Flowers said.
Most varieties are susceptible to the disease at early stages because temperatures haven't been high enough for adult resistance genes to kick in, Flowers said. Most farms are likely a week away from that resistance kicking in.
Flowers said most growers in Oregon are already on their second application of fungicide and many will make a third application, which is extremely unusual.
Xianming Chen, research plant pathologist with USDA's Agricultural Research Service in Pullman, Wash., said cool and moist conditions will continue to be favorable for stripe rust through the end of May.
In most fields, the stripe rust is under control if sprayed. Very few fields haven't been sprayed, Chen said. Farmers who haven't should compare the cost of spraying to the potential for yield losses if they don't, Chen said.
"It can not only cause a problem in their fields, but also to their neighbors and potentially to the whole region," he said, noting rust spores can be carried by the wind.
Most fields were sprayed about a month ago, Chen said, but rust on upper leaves is a new infection. He cautioned that particularly in the Central Washington drylands fungicide no longer works after a month.