In the transition zone, a common practice is to overseed warm season bermudagrass (Cynodon dactylon) with cool season perennial ryegrass (Lolium perenne) to improve winter aesthetics on golf courses. Most golf revenue is generated during spring and early summer due to ideal weather conditions. Perennial ryegrass is needed to provide desirable quality and playing conditions for fairway turf but competitively injures bermudagrass during this period. Bermudagrass has the ability to recover from perennial ryegrass competition given enough time during the summer. It has been suggested that healthy bermudagrass needs 100 days of weed-free growth in summer, yet research has not been conducted to validate or test this claim. “Healthy” bermudagrass is a subjective term that is usually based on biomass accumulation, total nonstructural carbohydrate (TNC), and ability of plants to survive stresses such as cold, heat, or UV light. Our objective is to measure how duration of perennial ryegrass competition influences bermudagrass health.

Studies were conducted in Blacksburg, VA on Patriot bermudagrass at Virginia Tech's Glade Road Research Facility and on Midiron bermudagrass at the Turfgrass Research Center. Foramsulfuron (Revolver) at 17 oz/A, was applied at weekly intervals for 24 weeks between April 4 and August 29, 2006. To assess bermudagrass “health”, bermudagrass and perennial ryegrass cover was visually evaluated on September 29 and 80cm2 plugs of turf were collected from each plot on October 15 to assess dry biomass, TNC, and electrolyte leakage (following cold stress). Electrolyte leakage and TNC data are still being collected and will be discussed later. Data were subjected to analysis of variance using a repeated measures technique and regressions were used to describe effects of bermudagrass weed-free period on measured responses.