Plant Disease Cycle
Photo Credit: University of Missouri
Fortunately, it takes more than the presence of pathogens (disease-causing microorganisms) to bring on infection in lawns. You also need a host—grass susceptible to a particular pathogen—and environmental conditions that foster disease. Conditions favoring pathogens vary but generally include warm weather and extended periods of moisture from rain, humidity, irrigation, or poor drainage. Other conditions, such as drought and high heat, reduce the ability of the grass to fight off infection. These three elements—pathogen, host, and environment—make up the “Plant Disease Cycle.” Any one factor on its own cannot initiate disease—problems begin when all three come together.