Research was conducted in 2009 and 2010 to evaluate influence of imazosulfuron rate and application timing on weed control in drill-seeded rice at Stuttgart, AR, and to evaluate imazosulfuron-containing herbicide programs in drill-seeded rice at Keiser and Stuttgart, AR. Weed species evaluated included barnyardgrass, broadleaf signalgrass, hemp sesbania, and yellow nutsedge. Imazosulfuron applied at 224 and 336 g ai ha−1 during PRE, early POST (EPOST), or preflood (PREFLD) growth periods provided similar control of all weeds. Imazosulfuron applied EPOST or PREFLD controlled hemp sesbania and yellow nutsedge ≥ 93% both years at 5 and 7 wk after planting (WAP), except in 2009 when hemp sesbania control was ≤ 79% at 7 WAP. In 2010, because of inadequate rainfall, hemp sesbania and yellow nutsedge control with PRE-applied imazosulfuron was ≤29% at 5 and 7 WAP. Imazosulfuron plus clomazone PRE followed by (fb) quinclorac plus propanil EPOST and imazosulfuron plus quinclorac EPOST fb thiobencarb plus propanil PREFLD programs controlled hemp sesbania and barnyardgrass (in at least two site-years), and yellow nutsedge and broadleaf signalgrass (in at least one site-year) greater than or equal to clomazone plus quinclorac PRE fb propanil plus halosulfuron PRELD (standard program). No rice injury was observed with any herbicide program. Rice yield with all imazosulfuron-containing herbicide programs (6,630 to 8,130 kg ha−1) was similar to the standard herbicide program (7,240 kg ha−1). Imazosulfuron in mixture with clomazone, propanil, or quinclorac can be incorporated into herbicide programs of mid-South rice production for the control of broadleaf weeds and sedges.

Field experiments were conducted in 2006, 2007, and 2008 at the Louisiana State University Agricultural Center's Northeast Research Station near St. Joseph, LA, to evaluate imazosulfuron programs involving rate, application timings, and tank mixes for PRE and POST broadleaf weed control in drill-seeded rice. Imazosulfuron showed residual activity against both Texasweed and hemp sesbania. PRE-applied imazosulfuron at 168 g ai ha−1 and higher rates provided 83 to 93% Texasweed control at 4 WAP. At 12 WAP, Texasweed control with 168 g ha−1 and higher rates was 92%. Hemp sesbania control with 168 g ha−1 and higher rates was 86 to 89% at 4 WAP and 65 to 86% at 12 WAP. Imazosulfuron at 224 g ha−1 applied EPOST provided 84 to 93% Texasweed control and 82 to 87% hemp sesbania control, and it was as effective as its tank mixture with bispyribac-sodium. When applied LPOST, four- to five-leaf Texasweed, imazosulfuron alone at 224 g ha−1 was not effective against Texasweed and hemp sesbania, but did improve weed control when mixed with bispyribac-sodium at 17.6 g ai ha−1.