Both the U.S. Environmental Protection Agency and the California Department of Pesticide Regulation have approved the use change, according to a Valent spokesman.
Chateau already was labeled for use on non-bearing tree nuts.
The new label allows for in-season use after bloom, according to a news release.
Cheateau is a pre-emergent herbicide, meaning it is only active on weeds that have not yet germinated.
It provides long-lasting control of an array of summer broadleaf weeds, including purslane and spurge, according to the release.
Valent officials recommend tankmixing it with a post-emergent herbicide to provide even broader spectrum weed control, since the post-emerge picks up weeds that have already germinated.
Chateau contains the active ingredient flumioxazin and won't leach or volatilize, according to the release.