Stands of shrub can harbor fungus that devastates wheat
By MATTHEW WEAVER
AIRWAY HEIGHTS, Wash. -- Landowners will be responsible for removing barberry bushes as a way to help stop the stem rust that attacks wheat, a Washington State University Extension specialist says.
A yellow-wooded shrub, common barberry is a host for wheat stem rust. Removing barberry bushes stops the fungus from developing near wheat fields, said Diana Roberts, regional extension specialist at WSU's Spokane County Extension.
The Washington Noxious Weed Control Board recently listed common barberry as a Class C noxious weed, beginning in 2013. Counties will decide whether to enforce the barberry eradication rule. It will become the landowners' responsibility to remove barberry bushes as they occur, she said.
Over the past year, warm, wet summer conditions have led to stem rust outbreaks in Stevens, Spokane and Whitman counties, affecting 20 to 100 percent of the plants in a field. Stem rust can cause up to 100 percent yield loss.
Stem rust appears as rusty pustules originating on the wheat plant stem. It can also spread to the leaf and head.
Because dry summer nights are more typical, Washington isn't conducive to stem rust outbreaks. But the area does have the potential to develop new races of rust that could easily cross the Rocky Mountains.
"We do not want to be a nursery for new races of stem rust that are going to affect late-developing wheats in the Midwest," Roberts said. "It's a social responsibility as much as economic responsibility to ourselves we are concerned about."
Growers are advised to monitor their fields beginning in June, particularly after rains. Farmers are also asked to report barberry sightings to researchers.
Usually by the time farmers see the disease, they're in the middle of the preharvest interval for using a fungicide. Roberts recommended looking at the fungicide label to ensure applications are legal.
The researchers have found success cutting down the trunk of the barberry bush, applying the herbicides picloram or imazapyr to the stumps with a crop oil or applying imazapyr to the leaves.
Picloram is not recommended for foliar application because of drift potential.
Roberts provided the update on barberry control efforts during the Spokane County Crop Improvement Association annual meeting in Airway Heights, Wash.