ABSTRACT
Five experiments were conducted in Ontario, Canada from 2016 to 2018 to determine how doses of S-metolachlor and halosulfuron applied preemergence (PRE) should be adjusted to control specific weed species in white bean. S-metolachlor, halosulfuron, and S-metolachlor + halosulfuron caused minimal (1% to 4%) injury in white bean. Weed interference reduced white bean yield 54%. On average, weed interference with S-metolachlor and halosulfuron decreased yield 34% and 29%, respectively. In contrast, white bean seed yield was similar to the weed-free control with the S-metolachlor + halosulfuron tankmixes. S-metolachlor applied alone controlled A. theophrasti, A. retroflexus, A. artemisiifolia, C. album, E. crus-galli and S. viridis 0% to 3%, 78% to 93%, 0% to 9%, 5% to 15%, 97% to 99% and 96% to 98%, respectively. Halosulfuron applied alone controlled A. theophrasti, A. retroflexus, A. artemisiifolia, C. album, E. crus-galli and S. viridis 39% to 87%, 93% to 99%, 64% to 88%, 34% to 59%, 10% to 30% and 13% to 35%, respectively. S-metolachlor + halosulfuron tankmixes controlled A. theophrasti, A. retroflexus, A. artemisiifolia, C. album, E. crus-galli and S. viridis 47% to 94%, 98% to 100%, 78% to 94%, 37% to 78%, 94% to 98% and 91% to 96%, respectively. Weed density and biomass reductions with the herbicides evaluated followed the same pattern as visible weed control assessments. Results from this study indicate that doses of S-metolachlor and halosulfuron, when applied as a tankmix, should be adjusted based on a weed species composition in each individual white bean field.