Research Update

Authors: Caleb Henderson, Will Poncy, and David McCall, Ph.D.

Spring dead spot (SDS) is the most economically important disease of hybrid bermudagrasses. Conventional treatment for SDS includes fungicide applications over an entire affected area. This leads many golf courses to use cheaper but less effective products to save money. Previous research from our lab indicated that precision management could be used to reduce the fungicides (by 65% in that study) while still maintaining SDS control similar to full-coverage applications. However, this utilized hand drawn maps which take time and expertise to generate. Last year we developed a Python script to automate the SDS identification process across fairways, and we now hope to test its capabilities in the field. In this study, we collected drone imagery from 16 golf course fairways at 3 locations across Virginia in the spring of 2021. Fairways were separated into one of 4 treatment types: No treatment, full coverage, spot treatment, and zonal treatment. Spot treatments were created with a 3 ft radius buffer around points generated by the aforementioned script and zonal treatments were selected based on density of detected points. Treated areas received 3.2 fl oz/1000 ft2 of Kabuto (Isofetamid) applied in the fall of 2021 applied using a Toro Multipro 5800 with Geolink GPS sprayer. Results imagery was collected in the spring of 2022 and all imagery was analyzed to determine the number of SDS patches within each fairway for both years to get percent change in SDS. Nontreated fairways showed an increase in SDS incidence. Spot and zonal treatments showed similar suppression to full-coverage applications while reducing the area covered between 10-85%, depending on disease intensity of each fairway. In May 2022, we applied these approaches to all golf course fairways and roughs at Independence Golf Club in Midlothian, VA. The use of SDS incidence maps resulted in an 80% reduction in treated fairways in October 2022. These results highlight the possibility for precision treatment of turfgrass pests in controlling environmental input and reducing cost. We hope this research can help to influence turfgrass managers to adopt this precision sprayer technology to more efficiently maintain their fields.