Submitted to: Washington Mint Drops
Publication Type: Popular Publication
Publication Acceptance Date: April 2, 2004
Publication Date: May 1, 2004
Citation: Boydston, R.A. 2004. Weed control notes. Washington Mint Drops. Spring 2004. p. 3. Technical Abstract: Weeds in spearmint and peppermint lower oil yield and quality. A popular herbicide, pendimethalin, is no longer available for growers to use this spring. As a result, growers must select among several older or several new preemergence herbicides that are now available. Trifluralin and napropamide are two older herbicides registered in mint that control weeds prior to weed emergence. However, both these herbicides work best when mechanically incorporated, which limits their use in mint. Terbacil and diuron selectively control a broad spectrum of weeds in mint and use of these herbicides may increase with the loss of pendimethalin. Two new herbicides have been registered for use in peppermint and spearmint production in 2004 ' clomazone and sulfentrazone. Both herbicides should be used only on dormant mint prior to the emergence of weeds. Clomazone, controls many annual grass and broadleaf weeds, including dandelions, volunteer alfalfa, tumble mustard, henbit, and downy brome. Clomazone can persist enough to injure wheat planted in the fall after a spring application. Sulfentrazone is primarily a broadleaf herbicide and it particularly strong on pigweed and nightshade species and also suppresses yellow nutsedge well. A terbacil resistant common lambsquarters biotype was identified in Washington State and growers should rotate herbicides with different modes of action to delay onset of herbicide resistant weed populations.