UW Researchers Seek Solution to Weed Resistance to Herbicides

University of Wyoming researchers will use kochia in a five-year study to help find a solution to weed resistance to herbicides.

Department of Plant Sciences Associate Professor Andrew Kniss has received a National Institute of Food and Agriculture grant to analyze methods of weed control other than herbicide.
Experimental kochia populations will be seeded in fields without major infestations, and all sites will be sprinkler irrigated, says Kniss, in the College of Agriculture and Natural Resources.

The populations will have herbicide-resistant and susceptible strains at a known ratio. The fields will be exposed to various treatments including crop rotation and tillage. Soil samples collected each fall will be used to record management practice data relative to kochia.

The sites are at research stations near Powell, Scottsbluff, Neb., and Huntley, Mont. The sites represent three different regions significantly affected by the study’s weed of choice.

Economic and biologic effects on kochia will be evaluated using statistical analysis on data collected in the field. Statistical modeling is the most commonly used tool because field study data is lacking due in part to difficulty and expense, Kniss says.

The economic impact of factors such as fuel, labor, fertilizer and crop prices will be determined.

“Diverse crop rotations and tillage are commonly recommended for management of herbicide-resistant weeds, but there is still not that much field-based information on how successful these approaches will be,” explains Kniss. “Since tillage and crop rotation are still quite common in our region, we thought this is a great opportunity to see how these practices actually influence development of herbicide-resistant weed populations.”

He says kochia is one of the most problematic weeds in Wyoming and many other western states.

“It infests both dryland and irrigated cropping systems and is particularly troublesome in sugar beet production,” Kniss says. “It has evolved resistance to many commonly used herbicides, including dicamba, atrazine and glyphosate. So any information we can learn about managing this species could have a big economic impact.”

Kochia was also chosen because it is an annual and produces an abundance of seed that remain viable only a few years in the soil. Because of these traits, Kniss expects meaningful results within the study’s five-year-time frame.

“At the conclusion of this research, we will have a much better understanding about how diverse crop rotations and tillage impact the evolution and spread of herbicide-resistant kochia populations,” says Kniss. “This will allow us to design the best combination of crop rotations, herbicides and appropriate use of tillage to minimize the impact of this weed. We will be developing an economic model that will help us understand the long-term benefit of adopting practices that reduce the likelihood of herbicide-resistant weed development.”

Kniss plans to report progress and findings annually beginning the second year of the study.