Relative tolerance of four cool-season turfgrass species to sulfosulfuron

Field experiments were conducted at Adelphia, NJ, in 2001 and 2002 to evaluate the response of Kentucky bluegrass, perennial ryegrass, tall fescue, and Chewings fine fescue to sulfosulfuron. Single applications of sulfosulfuron at 6 to 67 g ai/ha were applied to mature swards of each species. Visual chlorosis ratings were taken and clippings were collected 4 wk after treatment (WAT), and turf injury was rated 8 WAT. Chlorosis on all species increased with increasing sulfosulfuron rate. In 2001, Kentucky bluegrass, perennial ryegrass, tall fescue, and fine fescue chlorosis reached 33, 43, 65, and 61 % at 4 WAT, respectively, whereas in 2002, chlorosis only reached 13, 26, 46, and 26%, respectively. Clipping weights of all species decreased as application rate increased. Reductions in Kentucky bluegrass and perennial ryegrass clipping weights were less severe than those in tall and fine fescue. By 8 WAT, Kentucky bluegrass, perennial ryegrass, and fine fescue had nearly complete recovery from any initial visual injury symptoms. However, tall fescue injury was still evident 8 WAT in both years. Initial injury of Kentucky bluegrass, perennial ryegrass, and Chewings fine fescue was in the form of discoloration and stunting. Significant stand thinning was only evident in the tall fescue studies. These studies suggest that Kentucky bluegrass and perennial ryegrass may be more tolerant than tall fescue to applications of sulfosulfuron and fine fescue is intermediately tolerant to sulfosulfuron.