Field experiments were conducted from 2000 to 2002 at the Southern Maryland Research and Education Facility located in Upper Marlboro, MD to evaluate PPI and preemergence/prior-to-transplanting (PRE-T) applications of sulfentrazone in combination with clomazone or pendimethalin on crop injury and yield of Maryland-type tobacco. Pendimethalin was also evaluated alone. The highest levels of tobacco injury in 2000 occurred 3 wk after treatment (WAT) with PPI applications of sulfentrazone plus pendimethalin at 0.35 0.84 and 0.42 0.84 kg ai/ha, averaging 37 and 28%, respectively. In 2001, PPI applications of sulfentrazone plus clomazone at 0.42 0.84 kg/ha or sulfentrazone plus pendimethalin at 0.42 0.84 kg/ha caused 18 and 12% injury, respectively, 3 WAT. Injury in 2002 with all treatments averaged 7% or less 3 WAT. Greater rainfall through 3 WAT occurred in 2000 than in 2001 or 2002, likely contributing to the higher injury in 2000. Tobacco yields were generally similar among herbicide treatments in 2000 and 2001, and tobacco yields for all herbicide treatments were similar in 2002. The quality index was similar in 2000 and 2001, and varied slightly in 2002 among all herbicide treatments. Although a lower price was calculated for the nontreated controls, price did not vary among most herbicide treatments each year. This research shows that injury to Maryland-type tobacco can occur with sulfentrazone in combination with clomazone or pendimethalin, particularly when incorporated, and when high rainfall occurs soon after transplanting. However, injury is transient and generally has no negative influence on tobacco yield, quality, or price.

Nomenclature: Clomazone; pendimethalin; sulfentrazone; Maryland-type tobacco, Nicotiana tabacum L. ‘MD-609’.

Additional index words: Crop injury, crop price, crop quality, crop yield.

Abbreviations: DAT, days after treatment; PRE-T, preemergence/prior-to-transplanting; WAT, weeks after treatment; WATP, weeks after transplanting.