Dr. Pete's Turf Tips
Peter H. Dernoeden, Ph.D
As previously noted, lack of dew in circular or serpentine patterns on greens and elsewhere early in the morning is a good indicator that those areas will wilt rapidly as temperatures rise. Hand watering early AM and follow-ups of syringing should be performed as needed. Once wilt symptoms appear, affected areas should be spiked immediately, even if only via a pitch fork, and hand watered with hoses equipped with soil wetting agent pellets. Thereafter, a devoted, daily scouting program is needed, and “curative” management actions usually involve continued hand watering, spiking and drenching of a soil wetting agent. Hence, this is a heads-up for you who experience chronic LDS problems to get your “preventive” soil wetting agent program on schedule now.Localized dry spots (LDS) commonly appear during hot and dry periods of summer, but they also develop during unseasonably warm/hot and dry weather as early as May. Thatch producing annual bluegrass and creeping bentgrass are most commonly affected by LDS. Once LDS has severely damaged turf, it takes a monumental effort to revive affected areas. Courses with strained budgets often live with the ugly, dead spots until fall.
Localized dry spots are common on sand-based golf greens as well as green surrounds, collars (especially adjacent to bunkers) and approaches/aprons that have been topdressed with sand for several years. Localized dry spots do not develop in silt-loam soils, but they often develop within a few years after initiating a fairway sand topdressing program. Native sandy soil fairways in the coastal plain of the mid-Atlantic (e.g., coastal New Jersey and Delmarva) also develop LDS.
Symptoms of LDS first appear as blue-gray or purple-colored wilted areas that often have circular (i.e., patch) or serpentine patterns. Early morning scouting for LDS-affected areas usually reveals a lack of dew in patches. The diagnosis is simple via probing. In the case of LDS, soil inside wilted areas is bone dry; whereas, soil in adjacent green areas has adequate soil moisture. Affected areas soon turn brown, and if not properly attended to, will result in death and ugly dead spots for weeks or months to come.
The cause of LDS has been largely attributed to the decomposition activities of unidentified mushroom fungi in the same fungal group that cause fairy rings. This view is supported by the circular or serpentine patterns of wilted and dying grass. However, other microbes also are involved. The cause of turf death is drought stress and not pathogenic activity. Water repellency is induced by the breakdown of older fungal mycelium, and other sources of organic matter, which releases hydrophobic organic substances (e.g., fulvic acid) that coat individual sand particles. Individually coated sand particles pack loosely together, rendering soil impervious to water infiltration. The water repellent or hydrophobic condition normally is restricted to the upper few inches of soil. Removal of thatch-mat alone will not significantly improve water infiltration.
If your course experiences chronic LDS problems, the best management approach is to use a non-ionic soil wetting agent preventively, beginning several weeks in advance of anticipated symptoms. As previously noted, LDS can appear in May in our region, and if your course is subject to chronic LDS, it would be wise to begin your preventive soil wetting agent applications now. There are many products on the market and spray intervals vary. Generally, the longer the application interval, the more expensive the product. It is best to spike, core or otherwise create openings in the thatch/mat layer prior to application with most products. Once LDS appears, drenching higher rates in tighter spray intervals of wetting agents are required.
