More farmers fighting resistant kochia with crop management, diversity

More farmers fighting resistant kochia with crop management, diversity

Farmers using more glyphosate to fight resistance, but mixing in more modes of action to control stubborn weeds

Kansas farmers are responding to the emergence of glyphosate-resistant weeds with changes in the ways they manage weeds in their fields, according to research published in the most recent issue of the journal Weed Techology.

A survey conducted by researchers at Kansas State University in the fall of 2012 about weed management in western Kansas where glyphosate-resistant kochia is on the rise, revealed that crop revealed that many farmers are diversifying their herbicide choices as well as turning to tillage to manage resistant kochia.

Kochia is found in crop fields, rangelands, and pastures throughout the Great Plains, including the western United States and Canada.

RESISTANT KOCHIA: K-State researchers find that more producers are turning to diverse herbicides and even tillage to fight resistant weeds.

Glyphosate-resistant kochia was first discovered in Kansas in 2007. The survey showed that in the five years that followed, the percentage of fields infested by kochia rose from 47 percent to 70 percent. Survey respondents estimated that by 2012, one third of cropland in western Kansas was infested by glyphosate-resistant kochia.

During the same five-year period, growers increased their glyphosate use rates by 52 percent. They also increased the frequency of their glyphosate applications by 45 percent.

Though growers were using more glyphosate, the survey showed they also had diversified their weed management practices.

“In 2007 when the first glyphosate-resistant kochia was discovered, nearly half of Kansas fields received glyphosate-only weed control treatments,” said Phillip Stahlman, a Kansas State University weed scientist who co-authored the Weed Technology article. “By 2012, only 15 percent of fields received glyphosate alone.”

Survey respondents reported that tillage was proving to be the most consistently effective practice for managing glyphosate-resistant kochia.

Full text of the article, “Consultant’s Perspective on the Evolution and Management of Glyphosate-resistant Kochia (Kochia scoparia) in Western Kansas

Weed Technology, Vol. 29, Issue 2, April-June 2015, is now available.

Weed Technology presents original research on weed/crop management systems, herbicides, weed resistance to herbicides, and weed biology; reports of new weed problems, weed-related surveys, and new technologies for weed management; and special articles emphasizing technology transfer to improve weed control. The journal is a publication of the Weed Science Society of America. To learn more about the society, please visit: www.wssa.net.

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