Herbicide-resistant ryegrass targeted

"We think we have good justification to request a specific exemption for something to help growers with resistant ryegrass," says Alan York, North Carolina State University Extension weed scientist. York and other weed scientists from South Carolina, Georgia, Virginia, Arkansas, and perhaps other Southern states, went over data earlier this summer, anticipating writing up a request for a Section 18 exemption for use of Falcon, the proposed name of the Hoelon-resistant ryegrass material.

Bayer CropScience anticipates a label in 2004-2005, York says.

In North Carolina, Heolon-resistant ryegrass has traditionally been more of a problem in the western part of the state, York says. There, ryegrass first became resistant to Hoelon in the late 1980s. The problem has become increasingly worse. Pockets of ryegrass in eastern North Carolina are also resistant to Hoelon.

The weed scientists will be making the case for Falcon based on its performance over the past several years. A sulfonylurea, ALS inhibitor used with a safener, Falcon controls ryegrass as well as annual bluegrass.

"Timing is important with Falcon," York says. Previously, the material has been identified only by its code AE F130060.

York recommends applying the compound when the ryegrass is at three-leaf stage. "Apply this material before Santa Claus comes," York told participants on the North Carolina Small Grains Field Day at Circle Grove Seeds in Belhaven, N.C.

Its effectiveness decreases as it is applied later in the wheat-growing season. York reports about 96-percent average late-season ryegrass control over three research locations.

At the field day, York also gave a report on other products for Hoelon-resistant ryegrass. Achieve is registered for application to wheat and barley, but it’s generally not as effective as Hoelon. Moreover, it does not control Hoelon-resistant ryegrass.

Finesse is the only herbicide currently registered for control of Hoelon-resistant ryegrass. Ryegrass control has been variable. It suppresses ryegrass early in the season and can lead to increased wheat yields. Rotation is limited with Finesse, however.

Currently, in addition to Falcon, scientists in North Carolina are evaluating two control options for Hoelon-resistant ryegrass.

Axiom, which has received a Section 18 exemption for the past two years in Virginia, is applied from germination or spike to three-leaf stage of wheat. Axiom is a mixture of fluefaenacet and metribuzin and is manufacturered by Bayer CropScience. Inconsistency has been a concern for researchers. "If it rains, it works; if it doesn’t, it doesn’t work," York says. "On sandy land, we’ve had injury concerns."

"It’s a good product, but we’ve had results ranging from good to mediocre to poor with Axiom," York says.

Beyond, a Clearfield Systems product that is imidazolinone-resistant, received a label in January 2002. "It’s a respectable system," York says, "but the problem right now is you can’t get the trait into a wheat variety for our area. I don’t know when we’ll be able to get the trait into wheat varieties for our area."

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