Evaluations of S‐Metolachlor in flue‐cured tobacco weed management programs

AbstractEffective weed control is critical to growth and development of flue‐cured tobacco; however, current herbicide options are limited in commercial production. Field experiments were conducted from 2017 to 2018 to evaluate S‐metolachlor for use in flue‐cured tobacco weed management programs. Treatments included 10 herbicide programs: pretransplanted incorporated (PTI) applications of S‐metolachlor (1.07 kg a.i. ha–1) alone or in various combinations with sulfentrazone (0.18 kg a.i. ha–1), clomazone (0.84 kg a.i. ha–1), and pendimethalin (0.79 kg a.i. ha–1). S‐metolachlor and pendimethalin were also applied posttransplanting directed to row middles (POST‐DIR) following PTI applications of sulfentrazone + clomazone. A single posttransplanting over‐the‐top (POST‐OT) application of S‐metolachlor and a non‐treated control were included for comparison. The inclusion of S‐metolachlor in PTI herbicide programs did not improve weed control beyond the combination of sulfentrazone + clomazone. However, weed control after final harvest was improved by 8%, when S‐metolachlor was applied POST‐DIR. S‐metolachlor applied POST‐OT caused injury to tobacco plants (12%), although symptoms were transient with less than 2% visual injury 6 wk after transplanting. Due to increased weed control through harvest and the low injury potential, our results suggest that POST‐DIR applications of S‐metolachlor are the best fit for flue‐cured tobacco production when used in conjunction with recommended PTI herbicide programs.