By MATTHEW WEAVER
Pacific Northwest wheat farmers who mix fungicides with their herbicides will get earlier control of stripe rust this year, a researcher says.
But some farmers may have to spray their fields a second time with fungicide, depending on the weather and how stripe rust develops, said Xianming Chen, a stripe rust expert who works at the USDA Agricultural Research Service in Pullman, Wash.
He expects to make a recommendation on a second fungicide application in early May.
Chen and his research team recently found stripe rust in the Ritzville, and Odessa, Wash., areas, mostly on low leaves and actively producing rust spores.
Researchers found a lesser degree of stripe rust in Franklin County, east of Connell, Wash.
No rust was found in Whitman County, one of the highest wheat-producing counties in the nation.
It's a little earlier than normal to find rust in a commercial field, but Chen said the findings were not a surprise based on his previous forecasts. Rust was detected earlier and more widespread in 2011, he said.
Chen recommends applying fungicide with herbicides on fields with wheat varieties that are moderately susceptible to stripe rust.
Growers have done that in Adams and Lincoln counties and the Horse Heaven Hills area, he said.
If farmers aren't certain whether a variety is susceptible, they should contact Chen before applying herbicides.
Most wheat varieties have resistance that kicks in at a certain temperature, but the weather has not warmed up to that degree, Chen said.
Most of the rust already observed survived through the winter, because temperatures were relatively mild, Chen said.
Most of the infected fields were planted early, Chen said. Spraying early reduces the possibility of infecting other fields that were planted later. Rust is an airborne pathogen, so some rust could still spread around the region.
Previous long-term Pacific Northwest weather forecasts call for April and May to be relatively cool, Chen said. Some newer forecasts suggest warmer conditions than previous forecasts, but that doesn't change the stripe rust outlook much, Chen said. If April is warmer, that will help the rust develop faster, he said.
The rust outbreak is slightly more severe than last year. Chen predicts a yield loss of 44 percent on susceptible winter wheat varieties. Last year, varieties were expected to see a yield loss of 35 percent.