Winter critical for stripe rust
By MATTHEW WEAVER
Winter moisture and temperatures will likely determine the amount of stripe rust in next year's wheat crop, experts say.
Xianming Chen, research geneticist for the USDA Agricultural Research Service, said moderately resistant varieties didn't fare as well as they would have in a normal year, but most still demonstrated good resistance.
Despite the rust epidemic, most growers are enjoying good yields, Chen said, but the cost of fighting stripe rust has been high.
"Growers have spent big money on fungicide spray," Chen said. "Without spending that money, the yield loss can be very high."
With the late growing season, rust is still active, Chen said.
"September moisture is very critical for infection," Chen said. "If we have rain or showers very soon, we will repeat last year's situation."
A late harvest also increases the opportunity for a "green bridge," or the spread of the disease from the harvested crop to a planted crop, said Mike Flowers, Oregon State University extension cereals specialist.
Fall infections started the stripe rust epidemic last year, and the potential is there for a repeat, he said.
Chen recommends delaying planting about two weeks later than normal, but waiting too long could mean loss of soil moisture in dryland areas and affect crop emergence, Chen said.
There's not much need for treatments before next spring, Flowers said. During a fall infection, there's no economic damage. A cold winter could kill the rust. Last year, the infection survived the mild winter.
Flowers said he hopes more farmers plant resistant varieties, but there isn't a lot of seed available for the highly resistant varieties.
"We're still going to be at risk this year," he said. "Hopefully, in a two- to three-year cycle, we'll cycle all of these really susceptible varieties out of our portfolio."
Chen's research program continues to identify new genes and new sources of resistance. He supplies breeders with new germplasm to use in their programs.
Flowers advises farmers to monitor their fields closely. Growers should begin inspecting any variety for stripe rust, even the resistant ones, in February or March, he said.
"Hopefully everyone in the region now is tuned in to stripe rust and realizes the varieties we have are vulnerable," he said.