Weed control efficacy and dry bean response to preemergence herbicide incorporation timing

Field experiments were conducted in 2021 and 2022 to evaluate the effect of irrigation timing on S-ethyl-N,N-dipropylthiocarbamate (EPTC), flumioxazin, pyroxasulfone, and flumioxazin + pyroxasulfone weed control efficacy and safety in dry bean (Phaseolus vulgaris L.). Treatments consisted of EPTC (3430 g ai ha-1), flumioxazin (53.6 g ai ha-1), pyroxasulfone (119 g ai ha-1), and flumioxazin + pyroxasulfone (70.4 + 89.3 g ai ha-1) incorporated with overhead irrigation at 1, 4, and 8 days after herbicide treatment (DAT). A nontreated and hand-weeded check were included for comparison. Delaying irrigation until 8 DAT resulted in 11% and 19% injury in the pyroxasulfone and flumioxazin + pyroxasulfone treatments, respectively, but the crop recovered within 5 weeks after treatment. Delaying irrigation until 8 DAT increased total weed dry weight by 52%. Generally, flumioxazin + pyroxasulfone provided better weed control compared to flumioxazin or pyroxasulfone applied alone. Irrigation timing did not influence dry bean yield. Seed yield was 160 kg ha-1 in the nontreated check and 2521 kg ha-1 in the hand-weeded check. Seed yield in the flumioxazin + pyroxasulfone treatment (2425 kg ha-1) was similar to the hand-weeded check. Flumioxazin + pyroxasulfone provided very good weed control with acceptable crop safety. While irrigation timing may play a role in flumioxazin or pyroxasulfone injury, other soil and environmental factors may influence dry bean response to these herbicides. Delaying irrigation until 8 days after herbicide application resulted in 11%-19% crop injury. Delaying irrigation until to 8 days after herbicide application reduced stand density by up to 14%. Delaying irrigation until 8 days after herbicide application increased total weed dry weight by 52%. Flumioxazin + pyroxasulfone provided good weed control with acceptable crop safety. Irrigation timing did not influence dry bean seed yield.