Symptoms and Signs
Bacterial leaf spot infections start as small, dark specks on leaves. As disease develops, numerous water-soaked leaf spots appear. Leaf spots remain small (0.125 inch or 3 mm in diameter). Older leaf spots turn tan and may or may not have a purple border around them. Leaf spots are visible from both top and bottom sides of leaves. Symptoms on transplants may resemble downy mildew symptoms.
Comments on the Disease
Bacterial leaf spot is most often seen under greenhouse conditions. Occasionally, it also occurs on cauliflower in coastal valleys, but its occurrence in production fields is sporadic. The pathogen is seedborne and is splashed from plant to plant by rain and sprinkler irrigation.
Plant clean seed and disease-free transplants. Rotation away from fields where the disease has recently occurred may reduce inoculum levels in soil or infected debris. A change from sprinkler to furrow or drip irrigation may limit its spread. Cultivars vary in susceptibility.