Now is the time for alfalfa growers to be thinking about a residual herbicide application for control of tough winter weeds. Chateau® Herbicide provides growers with an effective tool against a broad spectrum of weeds, resulting in improved crop quality and increased profits at the time of first cutting.

By applying a residual herbicide such as Chateau in the fall, Western alfalfa growers can achieve long-lasting preemergence control of common groundsel, mustards and nettles, among other troublesome weeds. Growers in the Midwest, meanwhile, can control waterhemp, mustards, annual grasses and more by applying Chateau in early spring before alfalfa begins to regrow.

Experts say weed-free hay can command $30-$40 more per ton compared to dirty hay.

“If we don’t control winter weeds, the first two cuttings in spring will be full of weeds and the price growers can charge will go down. Weeds also tend to impact the longevity of an alfalfa stand. … Chateau has made its mark in being quite effective when applied in the dormant period here out West. Broadleaf weeds are of the most concern, economically speaking, and that’s where the strength of Chateau is. It gives growers an effective tool to keep their alfalfa clean.” —Mick Canevari, University of California farm advisor emeritus

The importance of being early

To best control winter weeds, experts recommend that growers make preemergence herbicide applications before those weeds have a chance to break through. New trials show that fall applications of Chateau (when paired with a burndown partner) result in maximum weed control.

“Getting herbicides out on the early side of weed germination is always—always—the best way to go. Early applications provide the best weed control and result in the cleanest-looking alfalfa. Applications beginning in October and into November have shown to be very effective. Any later and too many weeds have grown. Clean hay has more markets than dirty hay.” —Canevari

Chateau® Herbicide a “Complement” for Roundup Ready® Alfalfa

Amid the anticipation over the pending arrival of Roundup Ready® alfalfa, experts are cautioning against overreliance on glyphosate for weed control.

A preemergence herbicide such as Chateau, with its new mode of action in alfalfa, can serve as an important Roundup Ready alfalfa herbicide program partner. Chateau can help manage tough weeds such as fleabane and marestail as well as Palmer amaranth, which has already developed resistance to glyphosate in some areas.

“One concern with Roundup Ready alfalfa is that it would lead to exclusive reliance on glyphosate for weed control. Resistance can build with multiple exclusive applications. By incorporating Chateau in the late dormant season and coming back with glyphosate in late summer, they could complement each other.” —Dr. Dallas Peterson, Kansas State University extension weed control specialist

“Roundup Ready alfalfa is one of the most significant improvements in weed control in years. But we know from the Midwest that glyphosate-resistant weeds are increasing every year. We need Roundup Ready alfalfa, but to keep this technology effective we have to incorporate other herbicides—like Chateau—with it. Preemergence herbicides are absolutely necessary to piggyback on a Roundup Ready alfalfa program.” —Canevari

For more information on how Chateau can help manage tough weeds, visit

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