Arkansas Turfgrass – Eric DeBoer, Mike Richardson, Ph.D., and Doug Karcher, Ph.D.
The Arkansas climate is such that injury to warm-season turfgrasses is almost always a possibility during the winter months, especially in the northern region of the state. The most common causes of winter injury are sustained low temperatures, low temperature spikes, unseasonably warm temperatures followed by freezing temperatures, and turfgrass tissue desiccation. Certain species of turf have a better chance of surviving extreme cold temperatures than others. Turfgrasses that produce underground stems (rhizomes), such as bermudagrass and zoysiagrass, are better equipped to withstand extreme cold temperatures when compared to grasses like St. Augustinegrass or centipedegrass, which produce only aboveground stems (stolons). Many cultivars of bermudagrass, including Latitude 36, Northbridge, Riviera, and Tahoma 31, have demonstrated increased resistance to winter injury when compared to older bermudagrass cultivars. Certain site-specific characteristics can also play a role in determining the extent to which low temperatures will injure a stand of turf. Areas receiving large amounts of traffic, north facing slopes, heavily shaded areas, and poorly drained soils all have an elevated risk of winter injury.
Until now (mid-January at the time of this writing), the winter weather of 2018/2019 has been somewhat atypical in Arkansas. The duck hunters across the state can certainly attest that some early cool weather in November pushed a lot of ducks and geese into the state, but milder conditions in most of December and early January then slowed the migration considerably. As December and January are typically the coldest months of the year, we would normally expect a few extreme low-temperature periods during that time. This winter, we have only had a few days where low temperatures in the northern half of the state dipped below 20 °F and only one or two days where temperatures were near 15 °F (see Figure 1), which is the target temperature where we might expect some low-temperature damage. In addition, we have had over six inches of rain in most of the state since early December and that has been coming consistently from week to week, so concerns over excessively dry conditions and turf desiccation should also be at a minimum. Compared to last year, where we had extended periods of single-digit lows and very dry and windy conditions, we should be in much better shape coming out of this winter. Of course, turfgrass managers should not let their guard down as some cold weather (a few days of single-digit lows) is being predicted at the time of this writing. This is especially true for those maintaining ultradwarf bermudagrass greens.
There are multiple ways that golf course superintendents managing ultradwarf bermudagrass putting greens can assure themselves a great chance for winter survival and start the spring with a healthy stand of turf. First, invest in protective covers. The investment will pay for itself quickly when compared to the lost revenue from closing a golf course and renovating several putting greens. If the budget allows, putting greens should be covered when the low temperature is forecast to drop to 25 °F or lower. USGA-funded research from the University of Arkansas suggests the potential to lower this threshold as many as 10 degrees without significantly increasing winter injury. Special care should be taken to protect greens that reside in low-lying areas or shaded environments that may be prone to colder air and soil temperatures. During times of extreme low temperature predictions, many superintendents have minimized winter injury by creating a dead-air gap underneath their protective covers. Similar to the insulation provided by the air inside double-paned windows, an air gap underneath protective covers may help increase insulation during extreme cold events. Some materials that can be placed under covers to create a dead-air gap include pine straw, sections of drainage pipe, and pool noodles.
Second, pay close attention to winter moisture in putting greens. Desiccation of plant tissue during the winter months can contribute to winter injury as much as exposure to extreme low temperatures. Make sure to pay attention to the moisture on tops of undulations and places that are known to dry out first, as winter injury is common in these areas. USGA-funded research from the University of Arkansas also suggests potential benefits from applying a wetting agent to greens prior to the first covering event of the winter. It is also not uncommon for superintendents to make multiple wetting agent applications throughout the winter months to minimize the risk of localized dry spot formation.
With nearly two months remaining until the vernal equinox at the time of writing, it is still too far off to make predictions regarding the extent of winter injury that will be seen across the state of Arkansas this spring. Regardless, it is important to be proactive rather than reactive when it comes to dealing with potential turf winter injury situation. The following URL (https://horticulture.uark.edu/research-extension/turf/turftips/winterkill.php) points to a comprehensive UofA Turf Tip article with information about winter injury and a protocol for assessing possible winter injury without waiting until May to find out that you have significant winter injury on turfgrass stands.READ THE ISSUE