Submitted to: Washington Mint Drops
Publication Type: Popular Publication
Publication Acceptance Date: April 20, 2003
Publication Date: May 20, 2003
Citation: Mint Drops. Washington Mint Growers Association, pp. 3, Spring 2003. Interpretive Summary: Producers of peppermint and spearmint must control weeds to prevent losses in oil quality and quantity. Late spring is the time to begin scouting for weed emergence and anticipating weed control options for later emerging weeds and weeds that have escaped earlier control efforts. New weed species should be identified and controlled before they become major weed problems. Common early emerging broadleaf weed species such as, kochia, lambsquarters, Russian thistle, prickly lettuce, groundsel, and mustard species can be controlled with postemergence applications of Buctril, Basagran, Tough, Sinbar, and Stinger. All of these herbicides are most active when weeds are actively growing, not stressed, and when temperatures are warmer. Tank mixtures with Sinbar usually increase activity and weed spectrum, but chances of crop injury is also greater. Common summer annual and perennial grass weeds that have escaped preemergence applied herbicides can be controlled with postemergence applications of Assure II, Select, and Poast. A crop oil or surfactant recommended on the label should always be included. Do not apply these herbicides when grass weeds are water stressed, as activity will be lessened.
Technical Abstract: Weeds in spearmint and peppermint lower oil yield and quality. Late spring is a critical period for mint producers to access their weed problems and control weeds that have escaped preemergence herbicides applied in the dormant stage of mint growth. Bromoxynil, bentazon, terbacil, pyridate, and clopyralid are registered for postemergence broadleaf weed control in mint. Herbicide selection should be based on strengths of each herbicide and assessment of weed species present in individual fields. Perennial weeds, Canada thistle and yellow nutsedge, are suppressed well by two applications of bentazon. Common summer annual and perennial grass weeds that have escaped preemergence applied herbicides can be controlled with postemergence applications of quizalofop, clethodim, or sethoxydim. These herbicides work best when grass weeds are not water stressed.