As disease progresses, spots enlarge and become gray in the center with small black dots. Severely infected plants are stunted and may have a constricted stem at the soil line. Apply fungicides when needed. Maintain soil pH at or above 7.3 with hydrated lime. Fusarium oxysporum f.sp.
Symptoms first appear as a yellowing of lower leaves.
Alternaria leaf and head spot are caused by the fungi Alternaria brassicae and A. brassicicola. Apply fungicides when needed. Downy mildew is caused by the fungus Peronospora parasitica. Symptoms first appear as a purplish, irregular spots on leaves and stems. In the early morning, a purplish, fluffy growth is evident on the underside of diseased leaves.