Clomazone for Control of Grasses in Flue-Cured Tobacco (Nicotiana tabacum) Seedbeds1

Abstract

Experiments were conducted in 1995, 1996, and 1999 to evaluate clomazone preemergence in flue-cured tobacco seedbeds. The seedbeds were fumigated with methyl bromide to kill all the weeds and other pests, and then the subplots designated as grassy were sown with a mixture of equal mass of crowfootgrass, goosegrass, and rhodesgrass. Clomazone rates were 0, 0.14, 0.28, 0.42, and 0.56 kg ai/ha for 1995 and 0, 0.42, 0.47, 0.52, and 0.94 kg ai/ha for 1996 and 1999. The rates of clomazone in 1996 and 1999 were based on the 1995 results where 0.42 kg/ha decreased the dry mass of grasses by 98% compared with the nontreated control, while clomazone at 0.28 kg/ha decreased the dry mass of grasses by 75%, and this was not considered adequate. In 1995, 0.56 kg clomazone/ha decreased the tobacco seedling number but had no effect on the growth of tobacco plants. In 1996 and 1999 clomazone had no effect on the number or dry mass of tobacco seedlings despite causing slight discoloration 4 wk after sowing at all rates in ...