Stripe rust forecast low, but that could change

Little stripe rust is predicted so far this year, but that could change, a USDA researcher says. He recommends that farmers monitor their fields and keep an eye on the weather to gauge whether the rust outlook will change.

The first stripe rust forecast of 2018 for Pacific Northwest wheat is low, but a researcher warns that could change.

The forecast indicates stripe rust will likely be in the “low epidemic level” range, with from 0 to 20 percent yield loss, said Xianming Chen, plant pathologist at the USDA Agricultural Research Service in Pullman, Wash. Highly susceptible winter wheat varieties would likely have 6 percent yield loss and other varieties would have less than 3 percent yield loss, he said.

If Chen’s forecast stands, he said, early fungicide application at the time of herbicide application would not be necessary. The forecast is based on November and December temperatures, Chen said.

However, forecasts can drastically change, he warned.

The latest prediction is similar to the forecast he issued at the same time last year, but a second forecast in 2017 was different from the first.

“Last year, the rust was very severe,” Chen said.

His next prediction will be based on the entire winter. Winter weather determines how much rust survives, Chen said. The disease is more likely to survive with a good snow cover.

“This year, so far, there’s not very much snow cover,” he said.

The temperature also determines rust survival. Rust does not survive temperatures lower than 5 degrees Fahrenheit.

The picture will be clearer in March, when he issues his updated forecast, he said.

Don Drader, agronomy service representative for Syngenta in Moses Lake, Wash., advised farmers to follow rust reports from Chen and from Oregon State University.

They should also start scouting their fields now, he said. Rust spores can be viable during warmer periods. He recommends farmers check the draws, areas that get a little more humidity and look for foreign innoculants.

“The more frequently they can check them, the better off,” he said.

Growers also need to grow wheat varieties with rust resistance, he said.

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