Response of four market classes of dry bean to acifluorfen, bentazon, and bentazon/acifluorfen applied postemergence

Abstract

AbstractThree distinct studies consisting of a total of 11 field trials were carried out from 2016 to 2019 in Ontario to assess the tolerance of four market classes of dry bean to acifluorfen, bentazon, and bentazon/acifluorfen applied postemergence (POST) at various rates. In Study 1, acifluorfen (265 and 530 g ai ha−1) and bentazon (577 and 1144 g ai ha−1) caused up to 13% and 8% visible injury, respectively, but did not affect the relative stand, height, seed moisture, or yield of dry bean. Bentazon/acifluorfen (842 and 1684 g ai ha−1) caused up to 32% visible injury in dry bean but did not affect the relative stand, height, moisture, or seed yield except at the 2× rate which reduced dry bean biomass, height, and yield 43%, 11%, and 11%, respectively. The preformulated mixture of bentazon/acifluorfen caused a synergistic increase in dry bean injury. In Study 2, acifluorfen (600 and 1200 g ai ha−1) and bentazon (1080 and 2160 g ai ha−1) injured dry bean up to 12% and to 9%, respectively, but did not affect the relative stand, height, moisture, or yield. Bentazon/acifluorfen (840 and 1680 g ai ha−1) injured dry bean up to 16% but did not affect the relative stand, height, moisture, or yield of dry bean except at the high rate which reduced biomass, height, and yield 17%, 9%, and 5%, respectively. In Study 3, acifluorfen (420 and 480 g ai ha−1) and bentazon (1080 and 2160 g ai ha−1) injured dry bean up to 24 and 16%, respectively, but did not affect the relative stand, height, seed moisture content, or yield except for the relative biomass which was reduced up to 17%. Bentazon/acifluorfen (840 and 1680 g ai ha−1) injured dry bean up to 45% but did not affect the relative stand, height, seed moisture, or yield except for biomass, height, and seed yield which were decreased 44%, 11%, and 12% at the high rate. This study concludes that acifluorfen alone or preformulated with bentazon applied POST at rates assessed cannot be safely used dry bean.