Effect of Varied Rates of Atrazine and Simazine on the Establishment of Several Zoysia Strains1

Two triazine herbicides, atrazine and simazine, were applied over freshly planted stolons of five different strains of zoysia. Herbicide rates ranged from 1.4 to 8.4 kilograms active chemical per hectare (1 1/4 to 7 1/2 lb/A). The variety ‘Meyer’ and the two experimental selections B52‐22(24) and B21‐15(4) showed good tolerance to herbicide treatments with excellent stolon survival and only moderate growth reduction at chemical rates needed for good weed control. The variety ‘Midwest’ and the selection B21‐15(22) were substantially less tolerant and showed severe damage from treatment at this stage. Atrazine was more phytotoxic than simazine, especially on the less tolerant zoysia types.