Timing of cultural and chemical methods to remove perennial ryegrass overseeded in bermudagrass

Abstract Bermudagrass ( Cynodon dactylon L.) is a warm‐season grass that is often overseeded with cool‐season perennial ryegrass ( Lolium perenne L.) in the fall to provide green cover. Overseeded bermudagrass is desirable from late fall to early spring; however, turfgrass managers face challenges removing it in the spring and summer months. A 2‐year field study was conducted in northeast Mississippi to determine the most effective timing for removing perennial ryegrass and to compare removal methods for improving the bermudagrass transition. The plots were overseeded with perennial ryegrass in mid‐October of 2017 and 2018. Four removal timings of perennial ryegrass were performed from mid‐March to late May–early June. Five removal methods were evaluated, including fraise mowing at two depths (0.3 inches and 0.6 inches), weekly scalping to a height of 1 inches, two rimsulfuron applications applied 3 weeks apart, and one glyphosate application. The plots were assessed for turfgrass quality, perennial ryegrass cover, and overall green cover. In 2018 and 2019, 0.6‐inch fraise mowing resulted in the greatest perennial ryegrass removal within 1 week after treatment (WAT) compared with chemical removal treatments and weekly scalping; however, it also resulted in reduced green cover from 0 to 2 WAT compared with rimsulfuron application and the untreated control. March treatments generally resulted in higher perennial ryegrass cover at 8 WAT, whereas April, May, and June treatments resulted in <50% perennial ryegrass cover. Overall, the most effective timings for perennial ryegrass removal by chemical and cultural methods in northeast Mississippi were late spring and early summer. Effective methods that prevented long‐term delays in bermudagrass recovery depended on the timing of perennial ryegrass removal.