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Forage Grass Tolerance to Pasture Herbicides1
Brent A. Sellers and Jason A. Ferrell2Pasture productivity is a key component of cow-calf production systems in Florida. Weeds often invade and sometimes out-compete desirable forage species. Florida is unique in that many forage grasses are grown to compliment existing grazing systems. For example, Hemarthria (limpograss) is often grown in areas where drainage is poor, while bahiagrass is grown in most other areas. Some ranchers also grow cultivars of stargrass and/or bermudagrass. Although weed competition varies depending on forage type, an herbicide application is often needed to keep the pasture at maximum productivity. This publication describes the tolerance of forage cultivars grown in Florida to herbicides currently registered for use in pastures.
Not all cultivars of a particular forage species respond similarly to a given herbicide ( Table 1 ). Argentine bahiagrass tolerates most pasture herbicides except Journey and Roundup, while Pensacola may be severely injured by Cimarron, Cimarron Plus, and Cimarron X-tra. All herbicides may be used on stargrass and bermudagrass, with some level of injury from Velpar. Note that Journey is only labeled on Coastal bermudagrass. Hemathria, also known as limpograss, is the most sensitive to herbicide applications of all forage grasses grown in Florida.
It is important to realize that the response observed from an herbicide application can be variable. For example, the chance for forage injury can increase or decrease as the rate of herbicide applied either increases or decreases. Additionally, environmental conditions such as high temperature and high relative humidity may increase the potential for herbicide injury. For example, we have observed little or no injury to limpograss from 8 pt/acre 2,4-D amine when applied under cooler conditions, while 4 pt/acre in warmer weather caused moderate to severe injury.
The response of forages in Table 1 is for established forage cultivars. However, 2,4-D + dicamba (2 pt/acre) can be applied to sprigged forage cultivars, except for limpograss, 7 days after planting/sprigging. A forage can be considered established when at least 3 tillers are present on bahiagrass or at least 6 inches of new stolon growth is present on sprigged forages.
Figure 1. Tolerance of established (for at least 6 months) forage cultivars to commonly used herbicides.
Footnotes
1. This document is SS-AGR-87, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date November 2006. Revised January 2008. Visit the EDIS Web Site at http://edis.ifas.ufl.edu.2. Brent A. Sellers, assistant professor, Agronomy Department, Range Cattle Research and Education Center--Ona, FL; Jason A. Ferrell, assistant professor, Agronomy Department; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32610.
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U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.
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