Experiments were conducted at three locations in Louisiana from 1992 to 1994 to evaluate broadleaf weed control with sulfentrazone. Sulfentrazone at 0.42 kg ai/ha applied PPI or PRE provided at least 93% control of entireleaf morningglory in all years at all locations, which was greater than control with metribuzin PRE. Prickly sida control with sulfentrazone ranged from 83 to 94%, which was equal to or greater than control with metribuzin. Hemp sesbania and sicklepod control with sulfentrazone was unacceptable (≤75%) regardless of application method and generally was lower than control with metribuzin. Greater than 90% control of smellmelon and hophornbeam copperleaf was observed with all treatments. Minor but transient soybean injury was noted at one location in one year. Soybean yields following sulfentrazone PRE at St. Joseph were greater than yields with metribuzin as a result of the general increase in broadleaf weed control.

In 12 trials in Louisiana, sicklepod, entireleaf morningglory, pitted morningglory, and hemp sesbania control 4 wk after planting was greater with trifluralin applied PPI followed by chlorimuron plus metribuzin applied PRE than with trifluralin plus flumetsulam applied PPI. Sicklepod control with these herbicides was similar 6 wk after application. No differences in soybean yield were noted. Chlorimuron applied POST following trifluralin applied PPI and metribuzin applied PRE or trifluralin plus flumetsulam applied PPI improved weed control and soybean yield compared with soil-applied herbicides alone. Excellent barnyardgrass control was obtained with all herbicide programs.

Devil's-claw and smellmelon are summer annual broadleaf weed problems in the southwest cotton production region. Field studies conducted in 1993 and 1994 evaluated the efficacy of pyrithiobac for postemergence (POST) control of devil's-claw and smellmelon compared with soil-applied fluometuron or prometryn. Pyrithiobac at 0.07 and 0.14 kg ai/ha early POST and 0.14 kg ai/ha mid-POST controlled devil's-claw more than 84% at the late rating. Devil's-claw control with mid-POST applications of pyrithiobac at 0.07 kg ai/ha was reduced when compared with other rates and application timings. Smellmelon control with pyrithiobac ranged from 57 to 84% and, except when applied at 0.07 kg ai/ha early POST, was equivalent to or greater than either fluometuron or prometryn. Crop injury with pyrithiobac treatments 16 d after treatment was 5 to 13%, but 33 d later, was no more than 3%.