OREGON STATE UNIVERSITY

New wheats will help growers fight weeds

09/05/1997

PENDLETON, Ore.- Herbicide-resistant wheat that is in the research and development pipeline, and an experimental herbicide expected to be cleared for use, will give a big boost to growers' efforts to control weeds, Oregon State University researchers predict.

The combination will be especially effective on jointed goatgrass that infests most of the wheat-growing areas in the Northwest, they say.

But commercially acceptable herbicide-resistant wheat varieties for the Northwest are probably several years away, note enthusiastic scientists at OSU and the Columbia Basin Agricultural Research Center, headquartered at Pendleton.

"Preliminary trials show we can get excellent control of jointed goatgrass and other weeds by using herbicide-resistant wheat in combination with imazamox, a very effective experimental herbicide," said Dan Ball, an OSU weed scientist at the center.

Ball has been testing a French hard red wheat variety made available by American Cyanamid. This fall tests will shift to screening early-generation soft white winter wheat materials that may be better suited to the Northwest. OSU wheat breeder Warren Kronstad is developing these.

"We do have one major problem to overcome," Kronstad said. "There appears to be an association between the genetic factor providing herbicide-resistance and red grain. Our markets require white grain rather than red. We can overcome the problem, but it will take a couple additional years."

Meanwhile, Ball is enthused about imazamox, which will be used on the new wheats. "It is highly effective on the grasses that can substantially reduce wheat yields," he said.

Imazamox has not yet been approved for use on wheat, but that approval seems likely.

"This herbicide is environmentally safe," Ball said. "In fact, it works because it blocks an enzyme pathway in plants that doesn't even exist in animals."

The herbicide is welcome news for those who have waged a futile war on jointed goatgrass. The insidious weed infests more than 5 million acres in the United States and spreads to the tune of 50,000 acres a year. "It's in every major wheat production area of Oregon and threatens every acre," Ball said.

Jointed goatgrass is a nemesis of wheat because it is such a close relative. In fact, one of the original parents of wheat was a goatgrass from the Middle East, where wheat had its beginning.

"It's been tough to come up with an herbicide selective just for the weed and not for the wheat, but now scientists have done it," Ball said.

Ball and OSU weed scientist Carol Mallory-Smith said imazamox applied to herbicide-resistant wheat also provides effective control of other weeds including downy brome, Italian ryegrass, volunteer barley and non-herbicide-resistant wheat.

Their weed trials have been carried out in Pendleton, Corvallis and Moro for two years.

"Because of these early OSU efforts, Oregon is one to two years ahead of all other states in development of the herbicide-resistant wheat strategy," Ball said.

Scientists call the potential new varieties "IMI-wheats" because of their resistance to imazamox. Three to four years of further testing is needed before release of commercially acceptable varieties to growers.

And then growers will have to give the IMI-wheats special treatment.

"Growers will have to fully segregate IMI-wheat from non-IMI-wheat and be sure imazamox applications are made only to IMI-wheat," Ball said. "Non-IMI-wheat would be severely injured by the herbicide.

"Also," he added, "wise management of imazamox will be required to prevent the development and spread of herbicide-resistant weeds."