The conidia then serve as the “secondary inoculum” for the disease and infect the plant further or other nearby plants for the rest of the growing season. Due to having this “secondary inoculum” this makes powdery mildew of carrots a polycyclic disease since it is able to infect further on in the growing season past the primary inoculum. The surviving conidia then overwinter and serve as primary inoculum in the spring to start the cycle all over again.
The process begins when conidia infect the plant and become the “secondary inoculum”, leading to further infections or spread to nearby plants throughout the growing season. As a result, powdery mildew of carrots is considered a recurring disease because it can continue to infect beyond its initial phase. The surviving conidia then overwinter and restart the cycle in the spring.