The goal of this research was to develop herbicide programs for controlling acetolactate synthase (ALS)–, propanil-, quinclorac-, and clomazone-resistant barnyardgrass. Two applications of imazethapyr alone at 70 g ai ha−1 failed to control the ALS-resistant biotype more than 36%; however, when imazethapyr at 70 g ha−1 was applied early POST (EPOST) followed by imazethapyr at 70 g ha−1 plus fenoxaprop at 120 g ai ha−1 immediately prior to flooding (PREFLD), barnyardgrass control improved to 78% at 10 wk after planting. When imazethapyr was applied twice following PRE or delayed PRE applications of clomazone at 336 g ai ha−1, quinclorac at 560 g ai ha−1, pendimethalin at 1,120 g ai ha−1, or thiobencarb at 4,480 g ai ha−1 control was 92 to 100%. A single-pass program consisting of a delayed PRE application of clomazone at 336 g ha−1 plus quinclorac at 560 g ha−1 plus pendimethalin at 1,120 g ha−1 plus thiobencarb at 4,480 g ha−1 controlled all herbicide-resistant barnyardgrass biotypes at the same level as a standard multiple application program.

Research was conducted in Mississippi in 2012 and 2013 to compare the efficacy of saflufenacil to other broadleaf herbicides applied in mixtures with imazethapyr in a Clearfield rice system. Saflufenacil at 50 g ai ha−1, carfentrazone at 35 g ai ha−1, a prepackaged mixture of halosulfuron plus thifensulfuron at 35 plus 4 g ai ha−1, and a prepackaged mixture of propanil plus thiobencarb at 2,240 plus 2,240 g ai ha−1 were applied in mixture with imazethapyr at 70 g ai ha−1 early-POST (EPOST) to rice in the one- to two-leaf stage or late-POST (LPOST) to rice in the four-leaf to one-tiller stage. No differences in injury among the broadleaf herbicides or between application timings were detected at any evaluation. Imazethapyr combined with propanil plus thiobencarb or saflufenacil provided the greatest control of barnyardgrass 7 and 14 d after treatment (DAT). Hemp sesbania, ivyleaf morningglory, and Palmer amaranth control was greatest and similar for imazethapyr combined with carfentrazone, propanil plus thiobencarb, and saflufenacil; however, rough rice yield was greatest for imazethapyr combined with propanil plus thiobencarb or saflufenacil. Propanil plus thiobencarb or saflufenacil can be used in a Clearfield rice system to achieve optimum weed control and highest rice yields.