Efficacy of Trifluralin Compared to Ethalfluralin Applied Alone and Co-Applied with Halosulfuron for Weed Management in White Bean

There are a limited number of herbicides registered for weed management in white bean production in Ontario, Canada. Five field experiments were completed in Ontario from 2016 to 2018 to compare the efficacy of trifluralin and ethalfluralin applied alone and in combination with halosulfuron, applied preplant incorporated (PPI), for weed control efficacy and white bean tolerance and seed yield. At 2 and 4 WAE, there was no white bean injury from the herbicide treatments evaluated. Trifluralin applied PPI provided up to 32%, 99%, 13%, 99%, 27%, 99% and 99% control of velvetleaf, redroot pigweed, common ragweed, common lambsquarters, wild mustard, barnyardgrass and green foxtail, respectively. Trifluralin and ethalfluralin provide similar control of velvetleaf, redroot pigweed, barnyardgrass and green foxtail control, however, ethalfluralin is slightly more efficacious on common ragweed, common lambsquarters and wild mustard. Halosulfuron (35 g∙ai∙ha−1), applied PPI, provided as much as 76%, 98%, 96%, 96%, 100%, 19% and 23% control of velvetleaf, redroot pigweed, common ragweed, common lambsquarters, wild mustard, barnyardgrass and green foxtail, respectively. Trifluralin (600 or 1155 g∙ai∙ha−1) + halosulfuron (35 g∙ai∙ha−1), applied PPI, provided up to 88%, 100%, 98%, 100%, 100%, 99% and 98% control of velvetleaf, redroot pigweed, common ragweed, common lambsquarters, wild mustard, barnyardgrass and green foxtail, respectively. Ethalfluralin (810 or 1080 ai∙ha−1) + halosulfuron (35 g∙ai∙ha−1) provided similar control. Weed interference decreased white bean seed yield 44% - 45% with trifluralin, 30% - 41% with ethalfluralin and 34% with halosulfuron. However, decreased weed interference with trifluralin and ethalfluralin applied in combination with halosulfuron resulted white bean seed yield that was similar to the weed-free control. Trifluralin or ethalfluralin co-applied with halosulfuron can be safely used in white bean production for the control of common annual grass and broadleaf weeds in Ontario.

Influence of Herbicide Carrier on the Tolerance of White Bean to Preplant Incorporated and Preemergence Herbicides

Nine field trials (five with PPI and four with PRE herbicides) were conducted at Exeter and Ridgetown, Ontario during 2013 to 2015 to determine if the tolerance of white bean to preplant incorporated (PPI) and preemergence (PRE) herbicides is influenced by the herbicide carrier (water vs. UAN at 200 L•ha-1). There was no significant interaction between the carrier and herbicide for visible injury, plant stand, plant height, shoot dry weight, seed moisture content and yield. There was also no significant difference between the herbicide carriers for all parameters measured except for the shoot dry weight which was 6.5% greater when UAN was used as the carrier with PPI herbicides. Dimethenamid-p, pendimethalin, imazethapyr and halosulfuron applied PPI or PRE caused no visible injury except for imazethapyr PPI which caused 2% visible injury and dimethenamid-p PRE which caused 7% - 14% injury in white bean. There was no effect of the PPI and PRE herbicides evaluated on white bean stand, shoot dry weight, height, maturity and yield. Based on these results, using water or UAN could be used as the carrier for PPI and PRE herbicides in white bean.

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

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.