Strategies for Increased Yellow Nutsedge (Cyperus esculentus L.) Control with Halosulfuron and Sulfentrazone.

Yellow nutsedge (Cyperus esculentus L.) is one of the most widely distributed and troublesome weeds in the world. It competes against turfgrass for moisture and nutrients and reduces turf uniformity, visual appeal, and playability on golf courses and sports fields. Herbicide control of yellow nutsedge is inconsistent within regions and across the country, often failing to control regrowth after initial burn-down. Optimal application timing and strategies for halosulfuron and sulfentrazone have not been evaluated in Nebraska. Our objective was to evaluate herbicide application timing to develop strategies for yellow nutsedge control with halosulfuron or sulfentrazone. Single or sequential application (three weeks after initial application) of halosulfuron or sulfentrazone were made on 3 June, 25 Jun, 15 July, or 3 Aug in 2013, 2014, 2015 and 2016. Percent yellow nutsedge control was rated within the same growing season on 17 Sep and the following year on 3 June for residual control. Sequential application of halosulfuron with a three-week interval resulted in >95% control in our yellow nutsedge and turf mixture setting. We found herbicide control of yellow nutsedge using halosulfuron and sulfentrazone should be made at three to five leaf stage to maximize efficacy, both within the growing season and the following year. To better control environmental variability and isolate main effects and interactions, the study was duplicated in the greenhouse in 2017.