48th TWC, Tob. Work. Conf., 2018, abstr. 80

Flue-cured tobacco response to Rimsulfuron

North Carolina State University, Raleigh NC USA

Rimsulfuron (Matrix) is an ALS-inhibiting herbicide that is currently labeled for premergence (PRE) and postemergence (POST) control of select broadleaf and grass species in potatoes, tomatoes, grapes, and certain fruit crops. Rimsulfuron is used in numerous other products labeled for agronomic crops as a standalone herbicide or premixed with other herbicides as a preplant burndown, PRE, and/or POST use; depending on crop. Flue-cured tobacco has shown to be tolerant of over the top applications of similar ALS-inhibiting herbicides at labeled rates. Research was conducted in 2016 and 2017 in North Carolina across four environments near Kinston, Meadow, Oxford, and Whiteville. Treatments consisted of: clomazone plus sulfentrazone (PRE-T), sulfentrazone plus rimsulfuron (17g) (PRE-T), sulfentrazone plus rimsulfuron (34g) (PRE-T), clomazone plus sulfentrazone plus rimsulfuron (17g) (PRE-T), clomazone plus sulfentrazone plus rimsulfuron (34g) (PRE-T), clomazone plus sulfentrazone (PRE-T) followed by rimsulfuron (17g) (POT), clomazone plus sulfentrazone (PRE-T) followed by rimsulfuron (34g) (POT), sulfentrazone (PRE-T) followed by rimsulfuron (17g) (POT), and sulfentrazone (PRE-T) followed by rimsulfuron (34g) (POT). Clomazone and sulfentrazone were applied at labeled rates; 840 and 175 g ai ha-1, respectively. Pretransplant applications were applied 1 to 3 days before transplanting. Postemergence over-the-top (POT) applications were applied 3 weeks after transplanting. Visible estimates of percent crop injury and weed control were recorded bi-weekly and plant heights recorded 6 WAP. Yield, quality, and value was assessed from cured leaf. Clomazone plus sulfentrazone is considered the grower standard; therefore, this treatment was used as a check. No physical injury or stunting was observed with PRE-T applications of Matrix (alone or tank-mix) regardless of rate at any location. Early season injury from POT applications was observed; ranging from 6 to 33% depending on environment. Greater visual injury was noticed with 34 g ai ha-1 compared to 17 g ai ha-1. Injury observed included yellowing, leaf distortion and mottling, and plant stunting. Plant injury seemed to be transient, as 4 weeks after application injury dissipated. No difference in plant heights (6WAT) or yield, quality, or value was observed across all treatments. Annual grass control ranged from 88 to 97% and 92 to 97% at 2WAP and 7WAP; respectively. In general, greatest grass control 2WAP and 7WAP was observed when clomazone was included; while the lowest were tmts with sulfentrazone alone PRE-T. Despite significant early season injury from POT application the crop recovered and produced a yield similar to that observed with a traditional herbicide program. However, because of injury potential with POT applications, using rimsulfuron POT would not be a recommended practice. In regards to weed control, the addition of rimsulfuron did not increase control; however, it could be an acceptable tank-mix partner for residual control of certain weed species. (Reprinted with permission)