Timing of Sequential Applications for Nutsedge Control in Turfgrass

Abstract

Sequential applications of all of the ALS-inhibiting herbicides offered acceptable to excellent levels of nutsedge control in turf. Single applications generally provided nutsedge control for 2 to 6 weeks. Single applications of halosulfuron and flazasulfuron offered effective control for 2 weeks and less than 4 weeks. Effective nutsedge control by trifloxysulfuron and sulfosulfuron was observed at 31 days after treatment (DAT) and began to decline at 42 DAT. Sulfosulfuron at 0.094 lb a.i./A applied sequentially at either 4 or 6 weeks gave near complete nutsedge control at the end of the season at the end of September. A second application of trifloxysulfuron at 0.026 lb a.i./A at 4 or 6 weeks after a first application in mid-July resulted in controlling nutsedge better than 85% at the end of September. Flazasulfuron at 0.047 lb a.i./A applied sequentially at 6 weeks provided improving nutsedge control through the summer and resulted in near complete control at 95% at the end of September. Halosulfuron at 0.062 lb a.i./A showed only 65% control after the first application and a sequential application at 4 weeks improved control to 92% for only an additional 2 weeks and then control was less than acceptable at the end of the season. Imazaquin at 0.5 lb a.i./A gave less than acceptable but consistent control until sequential applications at both 4 and 6 weeks improved nutsedge control to acceptable levels.