| Experiments were established in producers' fields to evaluate the effects of late-season herbicide applications on the red rice and barnyardgrass seedbank. Glyphosate and fluazifop were applied once or twice, at 0.25, 0.5, and 1 times the labeled rate of 0.84 kg ae/ha and 0.21 kg ai/ha, respectively. Applications were made when annual grasses flowered; second application was 20 d later. Glyphosate applied twice each year at the 0.5 X rate reduced the barnyardgrass seedbank by 74%, but fluazifop applied sequentially at the 1 X rate reduced the seedbank only 7% after 2 yr. Glyphosate at 0.25 or 0.5 X reduced red rice seed production equal to fluazifop at 1 X, averaged across number of applications (<11 seeds/m2). Glyphosate timings on red rice seed production indicated that glyphosate (0.5 X) applied between 0 and 28 days after green ring (DAGR) effectively reduced red rice seed production. |
