Program Approaches to Control Herbicide-Resistant Barnyardgrass (Echinochloa crus-galli) in Midsouthern United States Rice

Abstract

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−1failed to control the ALS-resistant biotype more than 36%; however, when imazethapyr at 70 g ha−1was applied early POST (EPOST) followed by imazethapyr at 70 g ha−1plus fenoxaprop at 120 g ai ha−1immediately 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−1control was 92 to 100%. A single-pass program consisting of a delayed PRE application of clomazone at 336 g ha−1plus quinclorac at 560 g ha−1plus pendimethalin at 1,120 g ha−1plus thiobencarb at 4,480 g ha−1controlled all herbicide-resistant barnyardgrass biotypes at the same level as a standard multiple application program.