The Combined Effects of Drought and Disease on the Grass, Tall Fescue

Drought, along with other climate stressors, influences growth, photosynthetic ability, and resilience within plant communities. Plants are also susceptible to biotic stressors, including disease-causing fungal pathogens and pests. As the severity and frequency of these environmental stressors increases, it becomes more difficult to mitigate extreme weather events and negative consequences like growth loss, wilting, and disease susceptibility. For example, investigating the effect of drought on plant health is relevant for grass growth and preservation of vital crop grasses, but previous work often excludes the interaction of these drought conditions with disease causing pathogens. We studied these questions using tall fescue, a common drought-tolerant turf grass across the southeast United States, as a model host plant. We predicted that drought conditions would decrease the prevalence of the causal agent for brown patch disease, Rhizoctonia solani, on the host grass Lolium arundinaceum, commonly known as tall fescue, as the pathogen relies on water for dispersal. However, we expected the severity of disease lesions seen to increase due to the compiled host plant stressors of both disease and drought. We conducted a series of grow-room and field-based experiments to investigate the effects of a simulated drought environment and brown patch disease on tall fescue. From disease surveys in both environments, water treatment did not significantly affect disease prevalence or severity in tall fescue, but did significantly decrease leaf biomass for lab-grown plants. This indicates that while drought conditions may not increase effects from this fungal pathogen, there still are negative consequences to overall plant growth. Understanding these interactions is valuable for climate change mitigation, through effective water use and integrated pest management, in both turf and grassland environments.