White Bean and Weed Desiccation With Pelargonic Acid

Few studies have evaluated pelargonic acid for desiccating white bean and annual weeds. Five field experiments were conducted from 2021 to 2023 near Exeter and Ridgetown, Ontario, Canada to assess pelargonic acid applied alone or sequentially at different rates and several alternative herbicides for desiccating white bean and annual weeds. Pelargonic acid applied at 3400 g ai ha-1 desiccated white bean 88, 92, and 98% at 5, 8, and 14 days after application (DAA), respectively. Increasing the application rate, using sequential application, or adding 28% urea ammonium nitrate (UAN), did not improve white bean desiccation. Pelargonic acid applied at 3400 g ai ha-1 desiccated green pigweed 0, 2, and 1%; common ragweed 4, 3, and 3%; common lambsquarters 0, 0, and 0%; green foxtail 8, 12, and 15%; and barnyardgrass 5, 5, and 4% at 5, 8, and 14 DAA, respectively. Increasing the application rate, using sequential applications, or adding 28% UAN did not improve overall weed desiccation, except for green foxtail where desiccation was enhanced 14, 14, and 15% with pelargonic acid applied at 6800 g ai ha-1 at 5, 8, and 14 DAA, respectively and common ragweed where desiccation was increased 5% with pelargonic acid applied at 6800 g ai ha-1 at 8 DAA. At 14 DAA, green pigweed, common ragweed, common lambsquarters, green foxtail and barnyardgrass desiccation with carfentrazone-ethyl was 30, 6, 0, 11, and 7%; with ammonium salt of fatty acid was with 60, 12, 0, 59, and 36%; with flumioxazin was 54, 68, 31, 90, and 69%; with saflufenacil was 100, 96, 75, 37, and 55%; with tiafenacil was 100, 88, 5, 80, and 42%; with glufosinate was 100, 95, 100, 99, and 96%; and with diquat was 100, 99, 99, 99, and 96%, respectively. Dry bean desiccation with ammonium salt of fatty acid, glufosinate, carfentrazone-ethyl, flumioxazin, saflufenacil, tiafenacil, and diquat was 98-99% at 14 DAA. Among the desiccants evaluated, diquat and glufosinate were the most effective with 99% white bean desiccation and 95-100% desiccation of annual weeds at 14 DAA.