Two-Pass Weed Management Programs for White Bean

It is essential to implement effective weed management programs to minimize white bean yield loss from weed interference. Four field experiments were conducted during 2022 and 2023 to determine the efficacy of one-pass compared to two-pass weed control programs. This study evaluated trifluralin + S-metolachlor + imazethapyr or trifluralin + S-metolachlor + halosulfuron applied preplant incorporated (PPI), bentazon + fomesafen + quizalofop-p-ethyl applied postemergence (POST), and trifluralin + S-metolachlor + imazethapyr or trifluralin + S-metolachlor + halosulfuron applied PPI followed by (fb) bentazon + fomesafen + quizalofop-p-ethyl applied POST in white bean. There was minimal white bean injury (≤ 5%) with the herbicide programs evaluated. Weed interference decreased white bean yield 44%. Weed interference with bentazon + fomesafen + quizalofop-p-ethyl applied POST resulted in a 24% decrease in white bean seed yield compared to the weed-free control; however, all other PPI and PPI fb POST herbicide programs resulted in white bean seed yield that was similar to the weed-free control. Weed interference with the one-pass herbicide programs (PPI or POST) resulted in 17% lower white bean seed yield compared to the two-pass herbicide programs (PPI fb POST). Trifluralin + S-metolachlor + imazethapyr, applied PPI, controlled velvetleaf 85%, common ragweed 35%, common lambsquarters 96%, and green foxtail 80% at 8 weeks after the POST application (WAT). Trifluralin + S-metolachlor + halosulfuron, applied PPI, controlled velvetleaf 68%, common ragweed 87%, common lambsquarters 94% and green foxtail 56% at 8 WAT. Bentazon + fomesafen + quizalofop-p-ethyl, applied POST, controlled velvetleaf 86%, common ragweed 97%, common lambsquarters 34%, and green foxtail 29% at 8 WAT. Trifluralin + S-metolachlor + imazethapyr, applied PPI, followed by bentazon + fomesafen + quizalofop-p-ethyl, applied POST, controlled velvetleaf, common ragweed, common lambsquarters, and green foxtail 98, 97, 96, and 94%, respectively at 8 WAT. Trifluralin + S-metolachlor + halosulfuron, applied PPI, followed by bentazon + fomesafen + quizalofop-p-ethyl, applied POST, controlled velvetleaf, common ragweed, common lambsquarters, and green foxtail 97, 99, 97 and 93%, respectively at 8 WAT. Based on orthogonal contrast, the two-pass herbicide programs provided 17, 21, 20, and 38% greater control of velvetleaf, common ragweed, common lambsquarters, and green foxtail in comparison to the one-pass herbicide programs, respectively at 8 WAT. This study concludes that the two-pass herbicide programs of trifluralin + S-metolachlor + imazethapyr or trifluralin + S-metolachlor + halosulfuron applied PPI followed by bentazon + fomesafen + quizalofop-p-ethyl applied POST provides the most consistent weed control in white bean in Ontario.