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ARS Home » Southeast Area » Dawson, Georgia » National Peanut Research Laboratory » Research » Publications at this Location » Publication #256981
Title: Effect of cover crop and premergence herbicides on the control of ALS-Resistant Palmer Amaranth (Amaranthus palmeri) in peanut

Author
item DOBROW, M. H. - University Of Florida
item FERRELL, J. A. - University Of Florida
item Faircloth, Wilson
item MACDONALD, G. E. - University Of Florida
item BRECKE, B. J. - University Of Florida
item ERICKSON, J. E. - University Of Florida

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2011
Publication Date: 6/12/2012
Citation: Dobrow, M., Ferrell, J., Faircloth, W.H., Macdonald, G., Brecke, B., Erickson, J. 2012. Effect of cover crop and premergence herbicides on the control of ALS-Resistant Palmer Amaranth (Amaranthus palmeri) in peanut. Peanut Science. 38(1):73-77.

Interpretive Summary: Palmer amaranth is a troublesome species across most of the southeastern United States and has confirmed resistance to the ALS class of herbicides used in peanut and its most commonly rotated crops. Cover crop residues have many benefits to farmers but their interaction with soil-applied herbicides is relatively unknown. Field studies were conducted in 2007 and 2008 to determine the impact of three rye cover crop management scenarios combined with non–ALS residual herbicides on the duration of control of ALS-resistant Palmer amaranth. Cover crop scenarios included planting into a desiccated rye cover that was left standing, rolled flat, or no-cover. Within each cover crop scenario five soil residual herbicides were evaluated to determine the duration that each herbicide provided acceptable control of ALS-resistant Palmer amaranth. In 2008, cover crop did not affect the number of PFDs and data ranged between >67 and >3 days. In 2009, standing and rolled cover provided statistically greater PFD relative to no cover. But, herbicide efficacy was reduced in 2009 with PFD ranging between >16 and 0.3 days after treatment. In both years, PFD was ordered as flumioxazin>metolachlor (early POST)>metolachlor (PRE), norflurazon>pendimethalin. The purpose of this experiment was to determine the duration of control, not simply percent control, provided by various herbicides and whether cover crops significantly influenced this value. These data indicate flumioxazin applied PRE would require a POST application at an average of 16 to 67 days after application. Metolachlor + paraquat + 2, 4-DB applied AC provided an average of 23 days until threshold was achieved. It is necessary to start a weekly scouting regimen approximately 3 weeks after application in order to ensure that timely POST applications can be made to control ALS-resistant Palmer amaranth in peanut.

Technical Abstract: Palmer amaranth is a troublesome species across most of the southeastern United States. Resistance to acetolactate synthase (ALS) inhibiting herbicides has made control of Palmer amaranth even more difficult for peanut producers. Field studies were conducted in 2007 and 2008 to determine the impact of three rye cover crop management scenarios combined with non–ALS residual herbicides on the duration of control of ALS-resistant Palmer amaranth. Cover crop scenarios included planting into a desiccated rye cover that was left standing, rolled flat, or no-cover. Within each cover crop scenario five soil residual herbicides were evaluated to determine the duration that each herbicide provided acceptable control of ALS-resistant Palmer amaranth. Weed counts were conducted weekly to determine the number of Palmer amaranth free days (PFD), which equated to 1 Palmer amaranth per meter of row. In 2008, cover crop did not affect the number of PFDs and data ranged between >67 and >3 days. In 2009, standing and rolled cover provided statistically greater PFD relative to no cover. But, herbicide efficacy was reduced in 2009 with PFD ranging between >16 and 0.3 days after treatment. In both years, PFD was ordered as flumioxazin>metolachlor (early POST)>metolachlor (PRE), norflurazon>pendimethalin.