Strategies for Increased Yellow Nutsedge Control with Halosulfuron and Sulfentrazone.

Yellow nutsedge (Cyperus esculentus L.) is one of the most widely distributed and troublesome weeds in the world. In turfgrass it competes for moisture and nutrients, 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. Optimum application timing and rotation strategies of halosulfuron and sulfentrazone have not been evaluated in Nebraska. The objective of this study was to evaluate application timing and herbicide rotation of halosulfuron or sulfentrazone for yellow nutsedge control. In the first study, 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 and 2015. In a second study, single, sequential or rotated application of halosulfuron and sulfentrazone were made on 3 June or 15 July in 2013, 2014 and 2015. For both studies, percent yellow nutsedge control was rated until 17 Sep in each year. Results indicated control of yellow nutsedge using halosulfuron and sulfentrazone, should be made at the three to five leaf stage for maximize efficacy. Sequential application of halosulfuron with a six-week interval (3 June and 15 July) resulted in >95% control. Rotating application of halosulfuron and sulfentrazone on 3 June and 15 July, regardless of application order, resulted in >70% control. Results suggest that home users, lawn care professionals and golf course superintendents can rotate between the two herbicides. Rotation of two herbicides with different modes of action and application timing is critical for successful control and minimizing development of herbicide resistance.