By Alec Kowalewski, Chas Schmid, Brian McDonald, and Robert Starchvick, Oregon State University
Frost is a concern on northern and transition zone golf courses in the U.S. during the fall, winter and spring, as well as places with moderate winter conditions like the coastal Pacific Northwest and southern U.S which allow for continued play year-round. These areas alone account for 10,004 golf courses according to the 2017 Golf Course Environmental Profile. This concern has become more of an issue recently with the surge in golf since the COVID pandemic, and the high demand for tee times, even during winter months. The United States Golf Association (USGA) currently has conservative recommendations with respect to frost delays, suggesting significant delays on mornings with frost to avoid turfgrass damage; but it is not well understood what causes turfgrass injury, and the environmental conditions necessary for damage. Current recommendations are to delay the start of golf until after the frost has melted; however, there has been significant pushback from golfers who are skeptical as to whether these delays are truly necessary. It is also poorly understood how turfgrass species, mowing height, and source of traffic (foot traffic, cart traffic or maintenance equipment) affect turfgrass injury during frost. Frost delays, which are often early in the morning prior to golfer arrival, translate to significant reductions in revenue and valuable maintenance time.
In response to these questions, a series of preliminary studies were conducted at Oregon State University, Corvallis, OR in February 2022 at the request of USGA Agronomy and Research staff. Results from these initial explorations determined that foot traffic, equivalent to 16 golfers on a putting green, applied during eight frost events did not produce visual damage on annual bluegrass or reductions in normalized difference vegetation index (NDVI) values. Additionally, this initial work determined that as little as one pass of cart traffic during a frost event produced noticeable damage on a creeping bentgrass fairway. Considering these initial results, further exploration into the effects of golf cart and golf maintenance equipment traffic during frost is warranted. Therefore, the objectives of this project were the following: Evaluate the effects of 1) daily morning or afternoon winter cart traffic applied to a creeping bentgrass, annual bluegrass, and perennial ryegrass fairway, and 2) rolling applied to an annual bluegrass putting green. In 2024, an ancillary trial evaluating the effects of foot traffic applied to a creeping bentgrass and perennial ryegrass fairway was added. In 2025, an additional trial evaluating the effects of cart traffic applied to a perennial ryegrass rough will also be added.
Results (2023 to 2025)
Roller and cart traffic regularly reduced all putting green and fairway health, assessed using NDVI, in comparison to the nontreated control, particularly in the later part of the data collection period from February to early March 2023, 2024, and 2025 (Figures 1, 2, 3 and 4). Furthermore, morning roller and cart traffic typically produced greater reduction in turfgrass NDVI than the afternoon traffic. Foot traffic reduced NDVI values of a perennial ryegrass fairway in 2025 only, with the morning foot traffic producing a greater reduction in NDVI than the afternoon foot traffic. Creeping bentgrass fairways were not affected by foot traffic in 2023, 2024, or 2025.
In Corvallis, OR, in 2023, freezing morning soil and surface conditions were regularly recorded (Figure 1), while afternoon temperatures were above freezing. In 2024, freezing morning surface conditions were infrequent and freezing morning and afternoon soil temperatures were not observed. In 2025, freezing morning surface temperatures were regularly observed, while freezing morning soil conditions were not observed, and afternoon freezing conditions were observed on one day only. In multiple instances, four or more days of consecutive freezing surface temperatures, and sometimes soil temperatures, were followed by significant reductions in turfgrass NDVI values caused by roller or cart traffic. In 2023, 2024, and 2025 afternoon soil and surface temperatures, with the exception of one day in 2025, were above freezing. Despite the different trends in morning soil and surface temperatures observed across years, roller and cart traffic morning and afternoon generally reduced turfgrass NDVI values when repeatedly applied in the winter months, and morning traffic produced greater reductions in NDVI values than afternoon traffic particularly in February and March. While traffic on turf during freezing conditions does cause a decline in turfgrass performance, the risk of killing the turf is likely lower than current guidance suggest.