Peanut Response to Dicamba

E.P. PROSTKO*, T.L. GREY, University of Georgia, Tifton, GA 31793; M. MARSHALL, Clemson University, Blackville, SC 29817; J.A. FERRELL, University of Florida, Gainesville, FL 32611; D.L. JORDAN, North Carolina State University, Raleigh, NC 27695; B.J. BRECKE, University of Florida, Jay, FL 32583; P.A. DOTRAY, Texas Tech University, Lubbock, TX 79409; W.J. GRICHAR, Texas
AgriLIFE Research, Beeville, TX 78102; and G.R. WEHTJE, Auburn University, Auburn, AL 36849.

Dicamba (Clarity) is a postemergence, broadleaf herbicide used for weed control in grass crops. Herbicide tolerant broadleaf crops, such as cotton and soybean, are being developed with resistance to dicamba. Thus, it is speculated that there will be an increase in dicamba drift and tank contamination problems on peanut in the future. The response of peanut to low rates of dicamba has not been well documented. In 2008, field trials were conducted at nine locations across the Peanut Belt to evaluate the effects of dicamba on peanut growth, yield, and quality. Experiments were conducted in a randomized complete block design with a 3 X 6 factorial arrangement of treatments. Treatments included dicamba timing [30, 60, and 90 days after planting (DAP)] and dicamba rate (0, 1, 2, 4, 8, and 16 oz/A of Clarity 4SC). All treatments were replicated four times per location. The plot areas were maintained weed-free. Generally, peanut yields decreased with increasing rates of dicamba and peanut tolerance to dicamba increased as application timing was delayed. However, in 12 of 28 comparisons, peanut yield losses were greater when dicamba was applied at 60 DAP. When averaged across all locations and timings, even the lowest rate of dicamba (1 oz/A) caused a 13% peanut yield reduction (low = 0%; high = 25%). These results indicate that when peanuts are exposed to low rates of dicamba, significant yield losses can occur. Peanut growers must avoid dicamba drift and sprayer contamination problems

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