Recent research at Kansas State University has confirmed farmers' claims of reduced herbicide efficacy in controlling Palmer amaranth in fields. According to the research, Palmer amaranth samples, collected from a long-term conservation tillage study, were identified as being resistant to 2,4-D and dicamba. This is the first confirmed case of resistance to dicamba and 2,4-D in Palmer amaranth, further magnifying the challenge to manage this weed in conservation tillage systems.
Preliminary research also indicates that the same Palmer amaranth population survived application of group 27 (3 oz/a Callisto) and group 14 (10 oz/a Cobra) herbicides. Although resistance to group 27 herbicides in Palmer amaranth is increasing in Kansas, the sample population appears to have more survivors (88 percent) and a much higher level of resistance than previously reported. Additional research will be conducted to further determine the extent of herbicide resistance in the Palmer amaranth.
For more information, visit the K-State Agronomy eUpdate.