49th TWC, Tob. Work. Conf., 2020, abstr. 22

Efficacy of S-metolachlor based herbicide programs in flue-cured tobacco

BRADLEY A.; VANN M.C.; CAHOON C.W.; JORDAN D.L.; INMAN M.D.; CLAPP A.M.
North Carolina Cooperative Extension Service - Edgecombe County, Tarboro, NC USA

Maximized weed control is critical to the growth and development of flue-cured tobacco. Currently, the PPO-inhibiting herbicide sulfentrazone is the primary control option for Amaranthus, Cyperus, and Ipomea weed species. With the current risk of PPO-resistant Palmer amaranth, there is significant need for additional herbicides in tobacco production. Field experiments were conducted in four environments from 2017 to 2018 to evaluate S-metolachlor efficacy in flue-cured tobacco weed management programs. Treatments included S-metolachlor alone (1.07 kg ai/ha); Pendimethalin alone (0.79 kg ai/ha); Sulfentrazone (0.18 kg ai/ha) plus clomazone (0.84 kg ai/ha); S-metolachlor in combination with clomazone, sulfentrazone, and pendimethalin; S-metolachlor plus sulfentrazone plus clomazone; S-metolachlor POST-OT 7 days after transplanting; and sulfentrazone plus clomazone followed by S-metolachlor or pendimethalin POST-DIR at layby. All pre-transplanting herbicide applications were incorporated prior to bedding and a non-treated control was included for comparison. Season-long weed control, specifically Palmer amaranth, was greatest when sulfentrazone plus clomazone was followed by S-metolachlor POST-DIR at layby (95%). Additionally, S-metolachlor POST-OT provided excellent season-long Palmer amaranth suppression (93%); however, visual injury was noted two weeks following the application. Other treatments did not injure tobacco. Cured leaf yield, quality, and value were similar among herbicide programs, indicating S-metolachlor may prove useful in commercial tobacco production. (Reprinted with permission)