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Title: Comparison of fall and spring applied treatments of saflufenacil, glyphosate, dicamba, flumioxazin, pyroxasulfone, and rimsulfuron plus thinfensulfuron-methyl for glyphosate-resistant horseweed (conyza canadensis) control

Author
item DUCAR, J - Auburn University
item BURMESTER, C - Auburn University
item Price, Andrew
item MCELROY, S - Auburn University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2014
Publication Date: 3/1/2014
Citation: Ducar, J.T., Burmester, C.H., Price, A.J., Mcelroy, S. 2014. Comparison of fall and spring applied treatments of saflufenacil, glyphosate, dicamba, flumioxazin, pyroxasulfone, and rimsulfuron plus thinfensulfuron-methyl for glyphosate-resistant horseweed (conyza canadensis) control. Southern Weed Science Society. CDROM.

Interpretive Summary:

Technical Abstract: Two field studies were initiated in fall of 2012 at the Tennessee Valley Research and Extension Center in Belle Mina, AL and in a growers field in Cherokee County, Alabama to determine 1) the efficacy of glyphosate alone and in combination with dicamba and Saflufenacil to control glyphosate-resistant horseweed when applied in the fall and spring and 2) the efficacy of various residual herbicides to glyphosate-resistant horseweed when applied in the fall and spring. The following applies to both field studies. Plots measured 12 feet x 25 feet and were arranged in a randomized complete block with a split-plot treatment arrangement. The split-plots were application date (fall or spring) and herbicide treatment. Fall treatments for both trials were applied on November 17, 2012 and spring treatments were applied on March 20, 2013. Treatments for the first trial consisted of Roundup Powermax at 32 fluid ounces per acre, Clarity at 8 fluid ounces per acre, Clarity at 16 fluid ounces per acre, Roundup Powermax at 32 fluid ounces per acre plus Clarity at 8 fluid ounces per acre, Roundup Power max at 32 fluid ounces per plus Clarity at 16 fluid ounces per acre, Roundup Powermax at 32 fluid ounces per acre plus Saflufenacil at 2 fluid ounces per acre, and an untreated check. Treatments for the second trial Valor at 2 ounces per acre, Zidua at 2 ounces per acre, Leadoff at 1.5 ounces per acre, Sharpen at 2 fluid ounces per acre, and Fierce at 3 ounces per acre and an untreated check. Data were subjected to analysis of variance (ANOVA) and means were separated using Fisher’s Protected LSD at the 0.05 significance level. There was no application date and herbicide treatment interaction for either trial. In the first trial, all fall treatments controlled glyphosate-resistant horseweed at 171 DAT (days at treatment) 93% or greater except Roundup Powermax. All spring treatments provided greater than 97% control of glyphosate-resistant horseweed except Roundup Powermax. In the second trial, the fall applications of Leadoff and Fierce provided greater than 97% control at 171 DAT while Valor provided 87%, Sharpen provided 82%, Zidua provided 77% glyphosate-resistant horseweed control. The spring applied treatments all provided greater than 97% control except Valor which provided 74% glyphosate-resistant horseweed control. Data from this trial indicate that fall applications are a viable option for managing glyphosate-resistant horseweed. Being able to control horseweed early in the fall may be due to the smaller size of the weed.