Add kochia to the growing number of weeds that have become resistant to the popular herbicide glyphosate.

Worldwide, 17 weed species are not resistant to glyphosate, according to the Herbicide Resistance Action Committee. Some of those same weeds—including kochia--also are resistant to other modes of action.

Researchers at Kansas State University in Manhattan have confirmed at least five resistant populations in the western part of the state. Also known as fireweed, the drought-tolerant kochia grows on a wide range of cropland and non-agricultural sites in the Midwest and the West.

They suspect populations elsewhere in the state also may be resistant based on reports of poor weed control by producers, according to a news release.