Vol.3, No.4, 501-509 (2012) Agricultural Sciences doi:10.4236/as.2012.34059 Control of volunteer adzuki bean in soybean Christopher Kramer, Nader Soltani*, Darren E. Robinson, Clarence J. Swanton, Peter H. Sikkema University of Guelph, Ridgetown Campus, Ridgetown, Canada; * Corresponding Author: nsoltani@ridgetownc.uoguelph.ca Received 19 March 2012; revised 17 April 2012; accepted 20 May 2012 ABSTRACT The objective of this research was to evaluate the efficacy of various pre-emergence (PRE) and post-emergence (POST) herbicides for the con- trol of volunteer adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) in soybean (Glycine max L.). Trials were conducted at two locations in 2005, 2006, 2007, and 2009. Experiments were arranged in a randomized complete block de- sign with either five PRE or nine POST herbi- cides. Volunteer adzuki bean interference in soy- bean resulted in yield loss of up to 25%. Cloran- sulam-methyl, linuron, metribuzin, flumetsulam, and imazethapyr applied PRE provided up to 6%, 24%, 14%, 8%, and 0% control, respectively at 8 weeks after emergence (WAE), while acifluorfen, fomesafen, bentazon, thifensulfuron-methyl, clo- ransulam-methyl, imazethapyr, and imazethapyr plus bentazon applied POST provided 2%, 2%, 5%, 34%, 6%, 4%, and 12% control, respectively at 8 weeks after application (WAA). Generally, with the aforementioned herbicides, soybean yield was equivalent to the weedy control and soybean grain contamination with adzuki bean seed was consistently above the 1% maximum threshold. Chlorimuron-ethyl and glyphosate ap- plied POST provided up to 84% and 94% visual control at 8 WAA, respectively, decreased adzuki bean density, biomass, and seed production, and generally decreased soybean contamination with adzuki bean below the 1% threshold. The only herbicides evaluated in this study that con- trolled volunteer adzuki bean in soybean were chlorimuron-ethyl (9 g ai.ha -1 ) and glyphosate (900 g ai.ha -1 ) applied POST. All the other PRE and POST herbicides evaluated did not provide adequate control of volunteer adzuki bean in soybean. Keywords: Acifluorfen; Bentazon; Chlorimuron-Ethyl; Cloransulam-Methyl; Flumetsulam; Fomesafen; Imazethapyr; Linuron; Metribuzin; Pre-Emergence; Post-Emergence; Thifensulfuron-Methyl 1. INTRODUCTION Production of adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) in Ontario has grown over the last few years, and may continue to expand. From only 18 MT in 1994 [1], exports to Japan have reached approximately 5500 MT in 2005, with an additional 2500 MT exported to Taiwan [2]. Estimated land planted to adzuki bean in Ontario has ranged from 2500 to 4000 hectares between 2005 and 2008, and total production ranged from 4500 to 8500 MT [2]. While China exports a large amount of adzuki bean paste to Japan, Ontario has a 65% market share of global exports of unprocessed adzuki bean to Japan and Taiwan, with the USA and Australia providing the balance [2]. Adzuki bean produced in Ontario, Aus- tralia, and the USA is typically of higher quality than that of other locations [1]. Significant importers of adzuki bean include Taiwan and Korea, but Japan is the largest market for adzuki bean since there typically is a gap of 40,000 MT between annual consumption and domestic production [1]. Although it is still a minor crop, there is great potential for the adzuki bean acreage to increase in Ontario. Despite the opportunity to produce adzuki bean for export to Japan and Taiwan, a significant obstacle for Ontario growers is that volunteer adzuki bean plants will emerge in subsequent years. Adzuki bean pods shatter easily [3], which leads to significant seed losses prior to and during harvest. The seed coat of adzuki beans is hard in comparison to soybean and other legumes, reducing permeability to water and increasing the longevity of seed viability in the soil [4]. Anecdotally, growers have remarked that the presence of volunteer adzuki bean plants can still be an issue even 10 years after the last crop was grown. The actual potential for adzuki bean seed to remain viable in agricultural situations has not yet been documented, although recent laboratory studies have demonstrated that the seeds remain viable for at Copyright © 2012 SciRes. Openly accessible at http://www.scirp.org/journal/as/