Leaf symptoms appear as irregular brown spots, often beginning on the leaf margins. Spots coalesce and cause a leaf blight and dark brown streaks develop on leaf petioles. Floral parts may also be blighted. The bacteria also survives 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.
The pathogen is dispersed in splashing water. In most carrot-growing areas bacterial blight does not warrant control. In a few areas, such as the Antelope Valley, severe outbreaks may occur. Use furrow or drip irrigation rather than sprinklers. Turn under carrot residue to hasten decomposition.