By MATTHEW WEAVER
Stripe rust is spreading quickly on susceptible wheat varieties in Oregon State University test plots, extension cereal specialist Mike Flowers says.
Flowers provided an email update to industry members regarding signs of stripe rust and septoria on unsprayed South Willamette Valley variety trials.
If rust is showing up in his plots, farmers with susceptible varieties will likely be seeing the same thing, he said.
Syngenta's soft white winter wheat variety SY 107 and Syngenta AgriPro's AP Badger showed the most stripe rust, at 21.3 percent. OSU's soft white winter wheats Tubbs 06 had 18.8 percent, ORCF-102 had 17.5 percent and Goetze had 16.3 percent.
In Flowers' hard winter wheat trials, the West Bred hard red variety Rimrock had 23 percent stripe rust, followed by hard red winter Keldin at 20 percent and Whetstone with 18,8 percent.
Flowers observes the fields visually and estimates the percentage of leaves affected in a plot.
"Everybody that rates has a slightly different view," he said. "My 10 percent might be somebody else's 5 percent. I tend to rate a little harder than some other people, but it's all relative."
If a plot has less than 3 percent, that's essentially a pretty clean plot, Flowers said.
"It just means I was able to find some rust on a plant," he said. "When you start getting up above 10 percent, certainly into the 20 percent, those are the ones you really need to be worrying about."
There weren't many varieties with percentages of zero, Flowers said.
"It was kind of interesting to see that some of the varieties that have held up really well are showing some level of stripe rust," he said. "Very few varieties this year seem to be completely clean."
Flowers intends to send samples to USDA Agricultural Research Service plant research geneticist Xianming Chen in Pullman, Wash., for further testing. It could mean that the strains of the disease differ between eastern and western Oregon, which would not be surprising, he said.
Universities are focusing on more resistant lines, which means more choices for growers in the future, Flowers said.
Flowers expects to see signs of stripe rust beginning to pick up in nurseries in Milton-Freewater and Pendleton, Ore.
More varieties are beginning to have all-stage resistance, compared to high temperature adult plant resistance, since temperatures haven't yet increased to allow the high temperature resistance to kick in, Flowers said.
Farmers growing Goetze or AP Badger in the Willamette Valley have already applied fungicide to their fields once or twice for rust, he said. They will make another application for rust and septoria during flag leaf emergence.
If a variety rates higher for stripe rust, such as Tubbs 06, growers should be scouting for the disease and preparing treatment.
"If you haven't seen it already, it's very likely you're going to see it," Flowers said.
In both trials, the varieties Skiles, Norwest 553, UI SRG, IDO 1102, IDO 1103, IDO 816, IDO 1101, UI Silver, OR 2080227H, OR2080229H, OR2080236H, OR2090107H, OR210081H, Stephens, LW-10-1018, EXP-427 and OR2080637 all scored at 15 percent or higher for the wheat fungus septoria, a concern in western Oregon.
Flowers would expect to see about 10 percent normally. Higher percentages generally mean septoria moved into the upper canopy of the plants, perhaps due to the environment. Varieties with 5 percent or lower are essentially clean plots and show septoria was only on lower leaves.
Varieties are beginning to have improved genetic resistance to septoria, Flowers said.
Flowers said fungicides are effective against septoria, but recommends combining varieties with good stripe rust resistance and better septoria resistance. That reduces the likelihood of the need for an early fungicide application, he said.