2015
Risk of stacked dicamba and glyphosate resistance in kochia and best management practices
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Contributor/Checkoff:
Kansas Soybean Commission
Category:
Sustainable Production
Keywords:
AgricultureCrop protectionHerbicide
Parent Project:
Risk of stacked dicamba and glyphosate resistance in kochia and best management practices
Lead Principal Investigator:
Phillip Stahlman, Kansas State University
Co-Principal Investigators:
Mithila Jugulam, Kansas State University
Project Code:
1462
Contributing Organization (Checkoff):
Kansas Soybean Commission
(n/a)
Institution Funded:
Kansas State University
(n/a)
Brief Project Summary:

This research will establish a baseline of dicamba susceptibility in kochia prior to expected greater selection pressure following the commercialization of dicamba-resistant crops. Furthermore, the research will help determine whether populations from different geographical regions differ in response to dicamba and will measure differing response, if any, within populations. Results from field best management practices experiments will facilitate the development of effective management plans and stewardship guidelines for dicamba-tolerant crops. Results of these trials will be communicated to growers at Extension meetings and conference during winter months.

Key Benefactors:
farmers, agronomists, extension specialists, ag retailers

Information And Results
Final Project Results

Dicamba at 0.5 lb/A (16 fl oz) provided only 20% mortality and 50% reduction in biomass of surviving plants of the least susceptible population, which also is resistant to glyphosate. This and other supporting evidence confirms dicamba-resistant kochia presence in Kansas and highlights the importance of diverse management practices to prevent further evolution of kochia resistance to dicamba. The mechanism of resistance is not yet known, however related research on a population from Haskell County, Kansas indicates that dicamba resistance is not due to differences in uptake, translocation or metabolism of dicamba. Furthermore, another population from Finney County, Kansas was found to be resistant to four herbicide modes of action: synthetic auxins (dicamba), ALS-inhibitors (sulfonylurea herbicides), PSII inhibitors (triazine herbicides), and EPSPS inhibitors (glyphosate). This is the first reported case of resistance to four herbicide modes of action. Results confirmed earlier findings that dicamba was considerably more effective when applied preemergence than when applied postemergence, both in terms of plant mortality and plant fresh weight. This experiment confirmed the effectiveness of preemergence-applied dicamba in controlling kochia but also found differences in effectiveness among the accessions tested. The implications are that dicamba should only be used in combination with another herbicide mode of action to prevent selection for dicamba resistance.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.