Submitted to: Proceedings Mint Industry Research Council
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2004
Publication Date: 1/1/2005
Citation: Boydston, R.A., Baker, R. 2005. Weed research. Mint Industry Research Council 2004 Research Reports, Las Vegas, NV. p. 21.
Technical Abstract: Weeds present in mint reduce oil yield and quality of mint oil. Several weed species have developed resistance to, or are poorly controlled by herbicides labeled for mint production. Low rates of mesotrione and sulfentrazone were tested for weed control and mint tolerance in field trials. Low rates of sulfentrazone or mesotrione applied postemergence controlled pigweed with moderate peppermint or native spearmint injury. Flumioxazin impregnated on dry fertilizer was tested in peppermint and native spearmint. Flumioxazin applied on dry fertilizer did not control pigweed well likely due to inadequate soil coverage by fertilizer granules. Flumioxazin and sulfentrazone applied to dormant peppermint alone or in combinations with other herbicides labeled in mint, controlled common groundsel, Russian thistle, and prickly lettuce. Pronamide, diuron, terbacil, trifluralin, clomazone, and napropamide where tested in peppermint for white cockle control and mint tolerance. All herbicides caused little or no peppermint injury and controlled white cockle emerging from seed. Seven postemergence applied herbicides were tested on white cockle in green house trials. Dicamba, triclopyr, and paraquat controlled white cockle well. Imazamox, clopyralid, 2,4D-B, and MCPB only slightly injured white cockle. Peppermint and spearmint tolerance to dicamba and dicamba plus diflufenzopyr was tested in field trials. Dicamba applied to peppermint and native spearmint as dormant or early POST applications injured mint, but yield was not reduced at 0.25 lb ae/a rate. Dormant and early POST treatments of fluroxypyr were tested on a commercial field of Scotch spearmint and weed control, crop injury, and yield determined. Scotch spearmint was less tolerant to fluroxypyr than peppermint and native spearmint were in previous trials. Scotch spearmint was more tolerant to dormant applications or early postemergence applications of fluroxypyr than to later postemergence applications.