Chateau, a Valent U.S.A. Corp. broad-spectrum herbicide, has been labeled for use in alfalfa as well as in some fruit, vegetable and nut crops in many states.

It controls more than 90 annual weeds, including morningglories, nightshades, pigweeds, lambsquarters and annual grasses, company spokesmen say.

University of Arizona area agent Barry Tickes, in a December 2008 California Alfalfa Symposium proceedings paper, wrote that Chateau is effective on tough-to-control malva, groundsel and pigweed.

California researchers winter-applied the herbicide for control of winter-germinating weeds and grasses.

“Grasses are not its primary strength; however, it has shown extended grass control over Velpar, lasting into the first or second cutting of alfalfa,” according to a California Alfalfa Symposium paper by Mick Canevari and Jerry Schmierer, University of California farm advisors.

“Chateau can be tankmixed with other post and pre-emergent grass herbicides (Prowl, Prism, Poast) for a more-effective and longer grass-control program,” they added. It has a 25-day preharvest interval between cuttings, allowing use during the summer growing period.