Leaf Blight Symptoms on Carrot

Leaf Blight (fungus - Alternaria dauci) Infection occurs mostly on older leaves, but younger leaves may also become infected. Leaf blight first appears as indefinite brown to black areas with pale yellow centers. Infected leaves shrivel when infection is heavy. Under these conditions foliage appears as if burned by fire [Photo #2]. The fungus overwinters in infected crop refuse. Air-borne spores of the fungus are produced in large numbers on old lesions during periods of high humidity. Spores may also be carried on seed. The fungus requires moisture on leaves for infection. A preventative fungicide program should be followed where the disease is normally present, using a spray interval of 10 to 14 days.