Weed Management in White Beans with Soil-Applied Grass Herbicides plus Halosulfuron

There are a limited number of soil-applied herbicides available for broad-spectrum weed control in dry bean production in Ontario, Canada. Four experiments were conducted from 2017 to 2019 in southwestern Ontario to compare the efficacy of six soil-applied grass herbicides [trifluralin (600 g ai ha^-1), ethalfluralin (810 g ai ha^-1), pendimethalin (1080 g ai ha^-1), S-metolachlor (1050 g ai ha^-1), dimethenamid-p (544 g ai ha^-1) and EPTC (3400 g ai ha^-1)] and halosulfuron (35 g ai ha^-1) applied alone and in combination, applied preplant incorporated (PPI), on white bean tolerance and yield, and weed control efficacy. There was no white bean injury from the herbicide treatments evaluated. Grass herbicides (trifluralin, ethalfluralin, pendimethalin, S-metolachlor dimethenamid-P and EPTC) controlled velvetleaf 0% - 82%, pigweeds 87% - 99%, common ragweed 0% - 93%, common lambsquarters 81% - 99%, wild mustard 0% - 71%, barnyardgrass 98% - 100% and green foxtail 98% - 99%. Halosulfuron controlled velvetleaf 98%, pigweeds 94%, common ragweed 90% - 94%, common lambsquarters 97%, wild mustard 98% - 100%, barnyardgrass 19% - 24% and green foxtail 20% - 25%. Tankmixes of halosulfuron with soil-applied grass herbicides provided ≥93% control of the weed species evaluated. Reduction in density and biomass generally followed the same trend as visible control with herbicide treatments evaluated. Weed interference reduced white bean seed yield 70%. Seed yield was 53% - 66% of the weed-free control with trifluralin, ethalfluralin, pendimethalin, S-metolachlor