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.
Conidia that initially infect the plant become the “secondary inoculum”, causing further infections or spreading to nearby plants throughout the growing season. This characteristic makes powdery mildew of carrots a recurring disease, as it can continue to infect beyond its primary phase. The surviving conidia then serve as the starting point for the cycle in the spring.