It is important that preemergence herbicides used for annual weed control in warm- and cool-season turf not injure the desired turfgrass species. A field experiment was conducted for two years to determine the tolerance of Tifway bermudagrass [Cynodon transvaalensis Burtt-Davy x C. dactylon (L.) Pers.] and K-31 tall fescue (Festuca arundinacea Schreb.) to preemergence herbicides. Herbicides were applied at recommended (1X) and twice the recommended (2X) rates. Prodiamine (Barricade) at ≤ 1.6 kg/ha (≤ 1.5 lb/A), butralin (EXP 30910A and EXP 31068A) at ≤ 11.2 kg/ha (≤ 10.1 lb/A), pendimethalin (Pre M and Weedgrass Control) at 3.4 kg/ha (3.0 lb/A), and dithiopyr EC (Dimension) at 0.8 kg/ha (0.75 lb/A) on February 24 did not reduce the quality or shoot density of Tifway bermudagrass. Tifway bermudagrass injured by oxadiazon (Ronstar) ≥ 4.5 kg/ha (≥ 4.0 lb/A) recovered by late April to early May, while turf treated with oxyfluorfen plus oryzalin (Rout) at 2.2 +1.1 kg/ha (2.0 +1.0 lb/A) recovered by late April and turf treated at 4.5 + 2.2 kg/ha (4.0 + 2.0 lb/A) generally did not recover by late June. Tifway bermudagrass treated with oryzalin (Surflan) alone at ≤ 6.7 kg/ha (≤ 6.0 lb/A) did not recover by late June. However, turf treated with benefin plus oryzalin (XL) at 1.7 + 1.7 kg/ha (1.5 + 1.5 lb/A) recovered by this date. None of the preemergence herbicides severely reduced quality or shoot density of tall fescue except oxyfluorfen plus oryzalin (Rout) applied at ≤ 4.5 + 2.2 kg/ha (≤ 4.0 + 2.0 lb/A), oryzalin (Surflan) at 6.7 kg/ha (6.0 lb/A), and benefin plus oryzalin (XL) at 3.4 + 3.4 kg/ha (3.0 + 3.0 lb/A).
The author wishes to express his appreciation to J. Davis and M. Gilmer for providing assistance with statistical analyses and W. Olson and T. Dinkins for technical assistance.
2Professor, Department of Crop and Soil Sciences.