Weed control and peanut (Arachis hypogaea) response to sulfentrazone

Field experiments were conducted at several Texas peanut growing regions during the 1999 and 2000 growing seasons to study weed control and peanut response to sulfentrazone. Sulfentrazone applied preplant incorporated (PPI) or preemergence (PRE) caused up to 80% peanut stunt when rated 4-5 weeks after planting (WAP). The severity of stunting increased as sulfentrazone dose increased. Panicum texanum control was less than 40% regardless of dose. Cyperus esculentus control with sulfentrazone was better in south Texas than west Texas. In south Texas, C. esculentus was controlled at least 93% with sulfentrazone at 0.11 kg/ha or higher applied PPI or PRE when rated 4 and 12 WAP. Sulfentrazone at 0.06 kg/ha applied PPI controlled C. esculentus 93% 4 WAP but only 78% 14 WAP. The same dose of sulfentrazone applied PRE controlled yellow nutsedge 75% 4 WAP and 89% 14 WAP. In west Texas, C. esculentus control never exceeded 65% during the growing season regardless of dose or application timing. Ipomoea lacunosa control with sulfentrazone at 0.17 or 0.22 kg/ha was at least 90% season-long at both locations regardless of dose or application timing. The use of sulfentrazone in peanut in Texas is not recommended as it causes unacceptable crop stunting at the doses necessary for adequate control of various weeds.