Project Details - Full Facts for Selected Year
Information and Results
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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.
1. Determine dose response profiles of multiple kochia populations from throughout Kansas to dicamba and glyphosate individually and in mixtures to investigate reports of possible stacked resistance to both herbicides.
2. Evaluate various management practices to determine the most effective Best Management Practices (BMPs) to prevent the evolution and spread of dicamba resistance in kochia and maintain the utility and effectiveness of dicamba-tolerant crop technology.
Progress of Work
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.
Benefit to Soybean Farmers