Submitted to: Eastern Native Grass Symposium
Publication Type: Proceedings
Publication Acceptance Date: 9/27/2006
Publication Date: 10/13/2006
Citation: Myers, M.W., Adler, P.R., Curran, W. 2006. Evaluation of Weed Control During Switchgrass Establishment with Postemergence Herbicides. In: Sanderson, M.A., Adler, P., Goslee, S., Ritchie, J., Skinner, H., Soder, K., editors. Proceedings of the Fifth Eastern Native Grass Symposium, October 10-13, 2006, Harrisburg, Pennsylvania. p. 175.
Interpretive Summary: Not required.
Technical Abstract: Grass weeds can often pose a severe threat to the establishment of switchgrass, so identifying herbicides which can control grass weeds without inhibiting switchgrass growth would prove beneficial. Quinclorac and sulfosulfuron, recently labeled for CRP and seed production, were evaluated for use in establishment of switchgrass. These grass herbicides were tested in combination with broadleaf herbicides for both weed control and switchgrass seedling injury. All herbicide treatments were applied postemergence when the switchgrass seedlings were about 10-cm tall with three leaves. Weeds present at the time of application included common lambsquarters, redroot pigweed, fall panicum, witchgrass, and both yellow and green foxtail. Quinclorac at 8 oz/a alone provided 85% control of the foxtail species while providing less control of fall panicum and witchgrass (73%), lambsquarters (68%), and pigweed (67%). The addition of dicamba plus diflufenzopyr to quinclorac provided similar grass weed control as quinclorac and increased control of lambsquarters (92%) and pigweed (90%). The addition of metsulfuron and thifensulfuron significantly reduced the fall panicum and witchgrass control but did increase broadleaf control. Adding atrazine and halosulfuron to quinclorac did not provide any additional control versus applying quinclorac alone at 8 oz/a. Sulfosulfuron at 1.33 oz/a provided 70% control of fall panicum and witchgrass, 53% for foxtail species, 47% for pigweed, and 40% for lambsquarters. First year results indicate that quinclorac alone at 8 oz/a provided adequate control of foxtail species while maintaining crop safety. The addition of a growth regulator herbicide widened the spectrum of control. The use of grass herbicides along with proper crop management strategies such as proper planting dates, seeding rates, and seeding depth will prove to be valuable tools for successful switchgrass establishment.