Author(s)

Amit J. Jhala, Lowell D. Sandell, Greg R. Kruger

Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
West Central Research and Extension Center, University of Nebraska-Lincoln, North Platte, Nebraska, USA.

Control of glyphosate-resistant giant ragweed is a challenge, particularly for soybean growers, because of limited effective post-emergence (POST) herbicide options. Many soybean growers in no-till production systems use 2,4-D in burndown application for control of broadleaf weeds, including giant ragweed. Field experiments were conducted at David City, NE, in 2012 and 2013 to evaluate 2,4-D followed by PRE or POST herbicide programs for control of glyphosate-resistant giant ragweed in glyphosate-resistant soybean. Results suggested that burndown application of 2,4-D or saflufenacil plus imazethapyr resulted in 89 to 99% control of giant ragweed at 21 days after treatment. Burndown-only treatments of S-metolachlor plus metribuzin or sulfentrazone plus cloransulam resulted in poor control (≤65%) of giant ragweed and reduced soybean yield (≤ 577 kg·ha^-1). Burndown application of 2,4-D followed by saflufenacil plus imazethapyr, S-metolachlor plus metribuzin, or sulfentrazone plus cloransulam applied pre-emergence (PRE) or cloransulam, chlorimuron, fomesafen, imazethapyr, or lactofen in tank-mixtures with acetochlor applied POST resulted in 87% to 99% giant ragweed control, reduced density to ≤7 plants m^-2, and resulted in soybean yield from 2519 to 3823 kg·ha^-1. There was no difference among and between 2,4-D followed by PRE or POST herbicides for giant ragweed control, density, or soybean yield, indicating all the two pass herbicide programs were effective. It is concluded that glyphosate-resistant giant ragweed can be effectively controlled in soybean by including 2,4-D in burndown program followed by PRE or POST herbicides tested in this study.

Corn, Burndown, Giant Ragweed Biomass, Post-Emergence, Pre-Emergence, Resistance Management

Jhala, A. , Sandell, L. and Kruger, G. (2014) Control of Glyphosate-Resistant Giant Ragweed (Ambrosia trifida L.) with 2,4-D Followed by Pre-Emergence or Post-Emergence Herbicides in Glyphosate-Resistant Soybean (Glycine max L.). American Journal of Plant Sciences, 5, 2289-2297. doi: 10.4236/ajps.2014.515243.