Spring Pasture Weed Control

DR. ANTHONY OHMES

JACKSON, MO.
   Late February to mid-March is the recommended spring timing to control biennial and winter annual pasture weeds. The other recommended timing to control these weeds is in the fall. The reason for these timings is stage of growth and development of the target weeds. Applying herbicides to small actively growing weeds is critical to achieve maximum control and prevent seed production. Many biennial and annual winter weeds have two basic stages of development, which are basal rosette (vegetative stage) followed by bolting stalk (reproductive stage). For these plants the herbicide application timing would be the basal rosette stage. An example of this type of development is thistles.
   Products containing 2,4-D, dicamba, triclopyr, picloram, aminopyralid, or pre-mixed products containing two or more of these products provide good to excellent control of broadleaf weeds in pasture. Use caution: these products are safe at labeled rates on grass species but can kill or severely injure desirable broadleaves in grass-legume pasture mixes. In some cases spot treatment of areas may provide adequate control. Always read label for proper rates, target weeds, and grazing or harvest restrictions.
   In addition to herbicide applications, timely mowing will help suppress seed production. Successful mowing for seed suppression must occur prior to pollination. In many cases, a combination of both timely herbicide application and timely mowing will be needed during the growing season to manage weeds and improve pasture health.
   For more information contact a University of Missouri Extension Center and ask for IPM 1031: “Weed and Brush Control for Forages, Pastures, and Noncropland.” The MU IPM guide is a new publication and is an excellent resource for pasture management. You can also find it on the web at: http://extension.missouri.edu/p/ipm1031 . ∆
   DR. ANTHONY OHMES: Agronomy Specialist, University of Missouri