September is almost over and unfortunately, did not provide any fall like weather. The fall cool-down should be around the corner and those with cool-season grasses will be worried about cultivation and possibly lowering mowing heights. However, for warm-season turfgrass managers, the season of disease prevention is near. Currently soil temperatures in NC range from 74 to 82oF depending on where you are located in the state. Prevention of diseases such as spring dead spot, large patch, and take-all root rot are almost upon us.
Spring Dead Spot
Spring dead spot is arguably the most destructive disease of bermudagrass and zoysiagrass in the transition zone. The pathogen infects during the fall and predisposes the plant to winter injury. During the spring, circular patches of dead turf typically appear in both grasses maintained at heights conducive for lawns, athletic fields, golf course fairways or tees. On putting greens, the disease can manifest into circular patches, but also can develop in irregular patches that range from quite small to large affected areas.
Recent research out of Oklahoma State University by Dr. Nathan Walker demonstrated that infection was greatest with one of the spring dead spot pathogens when temperatures were at 65oF. Hence, we use a 70oF soil temperature threshold to initiate applications targeting spring dead spot. After the first application, the second application should be made 21 to 28 days after the initial application. Timing of the second application will depend on temperatures during the fall. Our trials on bermudagrass putting greens have shown excellent results applying the second application 21 days after the first. Products that have proven effective are Velista, Lexicon, Enclave, Posterity, Kabuto and Tekken. In order to be most effective, products should be irrigated in with at least 1/8 inch of water immediately after application. For more information on this disease, please visit: https://www.turffiles.ncsu.edu/diseases-in-turf/spring-dead-spot-in-turf/
Large patch is a disease that is most severe on centipedegrass, St. Augustinegrass and zoysiagrass. Even though bermudagrass is a host and has been frequently documented in NC, it is rarely managed because it typically grows out of the disease without much harm. Whereas the other three listed above struggle to recover from large patch. For zoysiagrass, targeting a 70oF soil temperature is also ideal for preventative control. The disease is so severe in centipede and St. Augustinegrass, the first applications should start when soil temperatures are between 75 and 80oF especially when soil moisture is high.
There are numerous products that are effective, but listed here are a few that have performed exceptionally well in our trials: Torque or Mirage (both are golf only use), Prostar, Heritage, Insignia, Lexicon, Headway, Trinity, and Fame. Recent research from Dr. Brandon Horvath at the University of Tennessee demonstrates that applications should be applied in at least 2 gallons/1,000ft2 in order to be effective. This list is not all inclusive, therefore for more information please visit:
Take-all Root Rot
Take-all root rot is a disease of ultradwarf bermudagrass greens and other warm-season grasses. The disease was commonly referred to as bermudagrass decline or root decline of warm-season grasses. We have already observed symptoms of this disease in our area, most likely as a result of the substantial rainfall from Hurricane Florence. Although fungicides may have been applied prior to Florence, those fungicides likely did not persist during the massive amount of rainfall most of the Carolinas received.
For our trials, we have targeted mid-October and mid-November for fungicide applications and last year those timings worked quite well. We are planning to conduct a timing trial over the next few years to determine a more precise window for managing this disease. This disease is an emerging problem in the Carolinas and we are working as fast as we can to develop management strategies for it. Currently the best products in our trials and in Dr. Bruce Martin’s trials at Clemson have been Lexicon, Briskway, Mirage, Tartan and Headway. We have typically reapplied fungicides on a 28-day interval and that suppressed the disease into late February the following year. During wet falls, more frequent applications may be necessary to suppress this disease. We will have a profile for this disease on Turffiles sometime this winter, so stay tuned!