Weed Control with Sulfentrazone plus a Low Rate of Imazethapyr in White Bean

Abstract

Ontario dry bean ( Phaseolus vulgaris L.) growers have few options for broadleaf weed control. Sulfentrazone is a group 14 herbicide that provides good control of several common Ontario weed species, and would provide another mode of action for broadleaf weed control if registered for use in Ontario dry beans. Five field studies were conducted during 2014 and 2015 to determine if a low dose of imazethapyr added to a tank mix of sulfentrazone + s-metolachlor would improve broadleaf control in white bean. Sulfentrazone (140 and 210 g · ai · ha ^-1 ) was mixed with imazethapyr and s-metolachlor and evaluated at 2 and 4 weeks after crop emergence for crop injury. Weed control was assessed visually at 4 and 8 weeks after herbicide application (WAA), and weed stand counts and biomass were determined at 8 WAA. Seed moisture and yield were determined at harvest. At 8 WAA, sulfentrazone (140 g · ai · ha -1 ) controlled pigweed species, common ragweed, common lambsquarters, wild mustard, barnyard grass and green foxtail 100%, 4%, 100%, 2%, 86% and 62%, respectively. The addition of imazethapyr (37.5 g · ai · ha -1 ) to sulfentrazone (140 g · ai · ha -1 ) improved the control of common ragweed, wild mustard and green foxtail by 19%, 98% and 33%, respectively. The three-way tank mix of sulfentrazone (140 g · ai · ha -1 ) plus s-metolachlor (1050 g · ai · ha -1 ) plus imazethapyr (37.5 g · ai · ha -1 ) controlled pigweed species, common ragweed, common lambsquarters, wild mustard, barnyard grass and green foxtail 100%, 35%, 100%, 100%, 96% and 100%, respectively. The tank mixes evaluated caused unacceptably high levels of crop injury; this study does not support the registration of sulfentrazone plus s-metolachlor + imazethapyr for use in Ontario white bean.