Illinois study shows management practices key to herbicide resistance

Scientists at the University of Illinois and the U.S. Department of Agriculture’s Agriculture Research Service (USDA-ARS) recently found that herbicide mixing, as opposed to herbicide rotation, might be the most effective tool in managing herbicide resistance.

Pat Tranel, a University of Illinois weed scientist and a co-author of a study published in Pest Management Science, said this was not the first time researchers have presented evidence that herbicide rotation is not the best resistance management strategy.

“This paper is valuable because these conclusions were obtained doing our experiment in a more ‘real-life’ fashion,” Tranel said. “This study confirmed previous conclusions that farmers should use herbicide mixing rather than rotation.”

During the study, the researchers evaluated glyphosate-resistance incidences, as well as landscape, soil, weed and farm-management data from 105 central Illinois grain farms, including almost 500 site-years of herbicide application records. This data, which was collected between 2004 and 2010, helped the researchers identify relationships between past herbicide use and current glyphosate-resistance occurrences.

“We looked at every factor we could think of in terms of management and landscape,” Tranel said. “We found that it was management factors that are the most important. It doesn’t matter whether you’re next to a water course that might bring in new seed, what the water hemp density of your field is, etc. It’s what you did in your field that matters.”