Otebo bean (Phaseolus vulgaris) sensitivity to pre-emergence herbicides

Field trials were conducted at two Ontario locations in 2003 and 2004 to evaluate the tolerance of otebo beans to the pre-emergence (PRE) applications of dimethenamid (1250 and 2500 g ai/ha), S-metolachlor (1600 and 3200 g ai/ha), clomazone (1000 and 2000 g ai/ha), and imazethapyr (75 and 150 g ai/ha). Dimethenamid and S-metolachlor caused 5% or less visual injury at 7, 14, and 28 days after treatment (DAT). However, this injury was transient with no adverse effect on plant height, shoot dry weight, seed moisture content and yield of otebo beans. Clomazone caused greater visual injury at 7, 14, and 28 DAT and reduced plant height by 10% and shoot dry weight by 25% compared to the non-treated check, though yield was not reduced. Imazethapyr caused visual injury, at 7, 14, and 28 DAT and the injury was persistent over time resulting in a decrease of up to 42% in plant height, shoot dry weight, and yield of otebo beans, respectively. Based on these results, dimethenamid and S-metolachlor applied PRE have potential for weed management in otebo beans. Additional research is needed to determine if there is an adequate margin of crop safety in otebo beans to the PRE application of clomazone. However, otebo bean did not possess an adequate margin of crop safety for imazethapyr at the doses evaluated.