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. Cauliflower heads and stems can be invaded internally by the downy mildew fungus. Physiological Disorders Broccoli suffers from brown bead, which can be caused by poor growth, disease, or excessive temperature It is typified by flowers that are small, turning brown, and not growing. The damage can be lessened by ensuring that crops receive enough nutrients. Cracking of the head , can occur when soil moisture is increased suddenly.