How to Manage Pests

Pests in Gardens and Landscapes

Downy mildew—Peronospora farinosa f. sp. spinaciae

Downy mildew causes light green to yellow angular spots on the upper surfaces of leaves. White fluffy growth of the fungus develops on the underside when moisture is present, but disappears soon after leaves dry. With time these lesions turn brown and dry up. Older leaves are attacked first. Severely infected leaves may die. On rare occasions the pathogen can become systemic, causing dark discoloration of stem tissue.

Life cycle


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. Use raised beds and avoid sprinkler irrigation. This fungus attacks only spinach; keeping spinach out of the garden for a year will lower disease incidence. 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 immediately. Resistant cultivars are available.

Yellow spots on upper surface of leaf
Yellow spots on upper surface of leaf

Statewide IPM Program, Agriculture and Natural Resources, University of California
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