Response of Zoysiagrass Cultivars to Preemergence Herbicides

Field experiments were conducted over a 2-year period to evaluate tolerance of two zoysiagrass (Zoysia spp.) cultivars to several preemergence herbicides. During April, May, and June 1993 and 1994, Meyer maintained a higher quality rating (7.5) than Korean common (6.9) when herbicide treatments were disregarded. None of the preemergence herbicides applied at recommended and twice the recommended rate reduced the quality of Meyer zoysiagrass at anytime and Korean common zoysiagrass during April and May, when compared with untreated turf. However, by late June, the quality of Korean common was lower in plots treated with benefin [N-butyl-N-ethyl-2,6-dinitro-4-(trifluoro-methyl)bezenamine] plus oryzalin [4-(dipropylamino)-3,5-dinitro-benzenesulfonamide] at ≤ 3.4 + 3.4 kg ha¯¹, oryzalin at ≤ 6.7 kg ha¯¹, and dithiopyr (EC) [S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridinedicarbothioate] at 1.6 kg ha¯¹, and dithiopyr (G) at ≤ 1.6 kg ha¯¹ than in untreated plots. None of the preemergence herbicides affected the density of either cultivar throughout the spring.