Spring. What an excellent time of year. Spring green-up and all of the new growth that comes with it puts almost everyone in a better mood with a sense of fresh excitement. The smell of fresh-cut grass in the spring—one can’t help being giddy about what it means, even those who suffer from Satan’s nasal dust (pollen) like me. Down south, there are the magnolias that suggest spring has arrived. Up north, the dogwood, apple, and cherry blossoms draw in crowds to also soak up the sunshine after a long winter of snow-cover that mostly keeps people from using recreational fields. Spring is magical here in the middle too, but it also comes with a couple of four-letter words for many bermudagrass athletic field managers: “Dead” and “Spot.”
Spring dead spot is typically a mild nuisance for turf managers in the Deep South when bermudagrass is never fully dormant but it is of great concern for those in the transition zone where bermudagrass completely shuts down each winter. Field managers in these regions typically begin thinking about the disease as their bermudagrass breaks dormancy everywhere except those ugly, bare, sunken circular patches sporadically placed across the playing surfaces. Their thoughts may include: How bad will it be this year? Will this make my field unsafe for athletes? How long will it take to recover? How many other four-letter words should I associate with this disease?
Sooner or later
I group bermudagrass-growing transition-zone turf managers into three categories: 1) those that have it each year, 2) those that have it bad each year, and 3) those that don’t have it yet, but will soon move to one of the former categories.
This disease is just as the name implies; dead spots in the spring, specifically on bermudagrass recreational surfaces. However, the problem develops in the fall and winter so management strategies are a bit tricky. One important consideration in managing this disease is that patches reappear in the exact same location for several years, gaining a little momentum each spring.
We have been battling spring dead spot for decades with mixed results at best. We’ve known about it. We’ve dealt with it. We’ve hated it. It always seems that with every step forward, there is a step or two backwards. There are some new and exciting fungicides out there that can be applied in the fall but it always comes with a caveat. “The product is too expensive to spray everything.” “The product doesn’t work consistently in my area.” “The product is only available for use on golf courses.” There is always something that prevents sports field managers from successfully and consistently suppressing the disease.
Our group at Virginia Tech is trying to tackle spring dead spot from several different angles to provide better management recommendations. We continue to investigate traditional methods for both suppression and recovery. But we’re also trying to think outside the box by blending technologies that are currently on the periphery of our industry.
Specifically, we are using drones to build disease incidence maps and GPS sprayers for targeted fungicide applications. Advancements in equipment availability, reduced costs, accessibility for rapid data processing, and improved understanding of how to integrate these technologies into our current management are paving the way for a brighter future. The process sounds complicated and developing the initial template was time consuming, but the concept is quite simple. Simply put, we are using these technologies to put the right product in the right place, at the right time.
Our research was conducted on five fairway sites within a golf course in Richmond, VA beginning in the spring of 2016 and continuing through 2018. The much-abbreviated version follows. We flew drones over a series of fairways each spring to collect thousands of images. These images were stitched together like a complex puzzle using post-flight imaging software and then the fun began. We developed a series of algorithms for our mosaicked images to digitally differentiate healthy bermudagrass from symptomatic spring dead spot and quantify the damage, with each pixel of our image having a precise GPS coordinate (within 3 inches of the actual location). This compilation of work resulted in a spatially accurate, georeferenced spring dead spot incidence map. We refined this procedure throughout the study so that we were could digitally analyze data within our research sites.
Each research site consisted of eighty 18 x 20-foot plots that received one of the following four treatments over 20 replications: 1) untreated control; 2) 3.6F Tebuconazole at 0.9 fluid ounce/1,000 square feet across the entire plot (blanket); 3) Velista at 0.7 wt ounce/1,000 square feet across the entire plot (blanket); and 4) site-specific Velista at 0.7 wt ounce/1,000 square feet based on historical disease incidence maps. We used the precise coordinates of each spring dead spot center with a 3-foot buffer around each patch for our targeted site-specific applications. Treatments were made in the fall when soil temperatures were consistently at or below 70F for 3 consecutive days using a GPS-guided Toro 5800 MultiPro sprayer with GeoLink, individual nozzle control, and RTK correction for enhanced GPS precision. We used the same georeferencing software to create a GIS layer of these plots that were used in conjunction with our incidence map. The spatial accuracy allowed us to know exactly where disease occurred the previous spring and our plot boundaries.
All this technology sounds cool if you’re a nerd like me but is meaningless if it doesn’t work. Fortunately for my career, it worked and it worked well. The most important take-home message of this research is that we were able successfully reduce our fungicide inputs by 65% without sacrificing control. We were able to use the right product (Velista, in this study) to control spring dead spot where needed (right place) in the fall after recording previous spring outbreaks (right time) at approximately one-third of the cost and still reduce disease compared to a cheaper alternative that can only be applied on golf courses. There are other effective new chemistries for spring dead spot suppression and these same principles should apply.
Adopting new innovations can be a hard pill to swallow, especially with so many unknowns. Things change over time and we all must adapt or be left behind. My primary focus used to be on effectively keeping grass alive and healthy. I still do this frequently but it has taken a back seat to effectively keeping my kids alive and healthy. I now spend a lot of time as a spectator on bermudagrass soccer fields watching my daughter, sometimes cringing when she runs across a sunken spring dead spot. I’m very fortunate; I’m able to merge these two interests by making the fields safer through addressing spring dead spot using some pretty cool technologies.
We’ve made a lot of progress in our ivory research tower but the technology will only make a difference when people start to adopt these uses. We will continue to refine our methods and apply them to other pest outbreaks while also working with turfgrass professionals to make these practices a reality. Since completing this project, we have flown 16 locations including some larger multipurpose sports complexes. More details of this project can be found at https://www.gcmonline.com/research/news/spring-dead-spot-management.
Like anything we do in research, there were a lot of people that made this happen. First and foremost are my partners in crime, Jordan Booth, CGCS, and Dr. Dana Sullivan, owner of TurfScout, LLC. They completed the hard tasks while I take the credit. We would like to thank the Environmental Institute for Golf and the Virginia Golf Course Superintendents Association for their financial support of this project. We would also like to thank The Toro Company and Syngenta Crop Protection for the use of products and services during this project. Many thanks to Christian Sain and David Rathke of the Country Club of Virginia for hosting this project. We would also like to acknowledge Wendell Hutchens, Travis Roberson, and numerous other individuals for continued contributions to the success of this project.
David McCall, PhD, is an assistant professor in Virginia Tech’s Department of Plant Pathology, Physiology, and Weed Science.