Bacterial leaf spot of carrot
Xanthomonas campestris pv. carotae
Xanthomonas campestris pv. carotae is seedborne, and survives on and is spread with carrot seed. The bacteria also survive in carrot debris but cannot survive in the soil in the absence of debris. Rain or sprinkler irrigation is required for optimum disease development. Warm weather favors infection and disease development. Optimum temperatures are between 77° and 86°F; infection does not occur below 65°F. The pathogen is dispersed in splashing water. Plant-to-plant spread may occur under heavy dew conditions.