Purple Nutsedge Control in Turfgrasses by S-21634

Field and greenhouse studies were conducted on S-21634 (1-methyl-4-phenylpyridinium chloride) for control of purple nutsedge (Cyperus rotundusL.) and tolerance of several turfgrass varieties and species. Purple nutsedge was controlled during the initial year of treatment with single applications of 3.4 and 5.6 kg/ha rates. All turfgrasses were injured following treatments, however, all except centipedegrass[Eremochloa ophiuroides(Munro) Hack.] had recovered in 7 to 8 weeks. In general, the injury to centipedegrass was higher and the turf density was lower in the treated plots at the final ratings. None of the treatments applied as a single S-21634 application affected root growth of bermudagrass (Cynodonsp.), ‘Emerald zoysia’ (Zoysia japonicaxZ. teniuflolia), centipedegrass, St. Augustine grass [Stenotaphrum secundatum(Walt.) Kuntze], or tall fescue (Festuca arundinaceaSchreb, ‘Ky 31′).