How to Manage Pests
Pests in Gardens and Landscapes
Downy mildew—Peronospora parasitica
Infections of downy mildew begin as irregular yellow patches on leaves; these chlorotic lesions later
turn brown. If conditions are favorable, white fluffy growth of the fungus develops on the undersides
of leaves. Leaves may take on a blighted appearance. Systemic infections can cause internal black streaks
and patches to form in stems and floret branches of broccoli and cauliflower.
The best way to prevent downy mildew is to avoid the environmental conditions that favor it. Freely circulating
air, allowing plants to dry between irrigations, and keeping leaves as dry as possible are good ways to
limit the disease. Cool, moist weather in early spring and late fall favor the disease, so adjusting planting
times may help in some areas. Destroy infected crop debris and susceptible related weeds before planting
a new crop. Resistant broccoli varieties are available.
caused by downy mildew on broccoli
cauliflower beneath cortical tissue