Preemergence pyrimisulfan applications affect purple nutsedge ( <i>Cyperus rotundus</i> L.) survival and reproduction

Abstract Purple nutsedge ( Cyperus rotundus L.) is one of the most problematic turfgrass weeds due to an elevated growth rate, aggressive rhizomes, and prolific tuber production. Currently, limited preemergence herbicide options exist for the control of C. rotundus . Therefore, research was conducted in the greenhouse to examine preemergence activity of pyrimisulfan on C. rotundus control and reproduction. Seven tubers were planted in 1‐L pots containing native soil. Treatments were initiated on July 14, 2021 and consisted of single and sequential applications of granular‐applied pyrimisulfan, liquid‐applied pyrimisulfan, and liquid‐applied pyrimisulfan + dithiopyr. Sequential applications were made on September 3, 2021. A nontreated check was added for comparison. Pots were destructively harvested 12 weeks after initial treatment (WAIT). Shoot dry biomass (g), rhizome dry biomass (g), tuber dry biomass (g), and tuber number were determined for each pot. Tubers were tested for viability (%) using tetrazolium chloride. All herbicide treatments reduced the number of emerged plants, shoot dry biomass, rhizome dry biomass, tuber dry biomass, tuber number, and tuber viability compared to the nontreated. A single application of liquid‐applied pyrimisulfan reduced the number of emerged plants by 99% 10 WAIT and viable tubers by 100% 12 WAIT, compared to a single application of granular‐applied pyrimisulfan (70% and 87%, respectively). Sequential applications of granular‐applied pyrimisulfan provided similar results as all liquid‐applied pyrimisulfan treatments across response variables. Neither a sequential application nor the addition of dithiopyr increased liquid‐applied pyrimisulfan efficacy.