The following is information on controlling Nutsedge in Turf.
Control options for the homeowner are rather limited; look for products with the active ingredient sulfentrazone or halosulfuron. Yellow nutsedge control options for professional applicators include Dismiss (sulfentrazone) and Sedgehammer (a.i. halosulfuron). Repeat applications will likely be required to achieve control. As with any herbicide applications at this time of year, be cautious of applications to turfgrass that is under drought or heat stress, even with the relatively cool temperatures, the soil is drying out in many areas and the turf is starting to show some stress. General recommendations are to avoid herbicide applications when temperatures are above 80 F due to the risk of burning the turf. Sulfentrazone has been implicated in causing damage to tall fescue turf in some cases, especially when applied with urea fertilizers.
Information in part from the Michigan State University Landscape Alert Site http://ipmnews.msu.edu/landscape/