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Pitch a change-up to fight resistant ryegrass

Ryegrass is somewhat of a controversial plant. It was introduced to Oklahoma and Texas as a forage crop for pastures, but it also has a dark side: When it gets into crops, it can spread fast and can be very hard to control. Overuse of herbicides has led to herbicide-resistant strains, compounding the problem more and forcing researchers at Oklahoma State University to look at the problem and find new methods of control.

“Ryegrass is kind of a new ballgame,” says Don Schieber, a producer near Ponca City, Okla., and vice chairman of the Oklahoma Wheat Commission. Schieber has traveled across the state and has seen firsthand the effects of ryegrass in wheat.

“We do harvesting across Oklahoma, and we’ve found it in a lot of the fields we harvested in two years ago. We didn’t have as much of a problem last year, but when it’s there, you got it. It’s kind of hard to reverse.”

“Cattleman like to spread it all over the place for winter pasture; it really puts on a lot of growth in the spring,” says Tom Peeper, a Warth Distinguished professor of agronomy in the Department of Plant and Soil Sciences at OSU. “The problem we get into is it’s a very aggressive weed in crops. It also has a nasty characteristic in that it develops a resistance to herbicide faster than any weed we’ve come across.”

The plant has developed a resistance to herbicides due to overuse, primarily sulfonylurea, or SU, herbicides. Producers tend to use SU herbicides due to their ability to control both grasses and broadleaf weeds.

But producers noticed more and more resistance, prompting Peeper and other researchers to look at the problem.

During summer 2008 they collected seed samples from 100 different locations in Oklahoma and planted them at the OSU research station in Perkins. They applied nine herbicides at the appropriate rates and times, and found the problems of why the herbicides weren’t working.

In 50% of samples using SU herbicides, the plants were resistant; about 20% were suppressed; and only 30% were controlled by the herbicides.

ACCase herbicides, like Axial or Hoelon, had much better results, with no resistance and a 94% control rate.

“We’ve caused the problems by overuse of SU herbicides,” says Mark Boyles, a statewide canola Extension specialist in the Department of Plant and Soil Sciences at OSU. “Excessive use of Finesse, Glean, Osprey and OlympusFlex — these are the big four that’s caused the problems."

Brazil writes from Stillwater, Okla.

This article published in the January, 2010 edition of THE FARMER-STOCKMAN.

All rights reserved. Copyright Farm Progress Cos. 2010.