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Pacific Pests, Pathogens & Weeds - Mini Fact Sheet Edition

Cabbage downy mildew (192)

Photo 1. Older leaves of cabbage seedlings showing speckled appearance caused by downy mildew, Hyaloperonospora parasitica.

Photo 2. Infection in the field: spots on the leaves caused by downy mildew, Hyaloperonospora parasitica, join together in wet weather and form large patches of decay.

Summary

Worldwide distribution. On brassicas, crops, weeds and ornamentals. An important disease in sub-tropics.
Yellow to pale brown spots develop into irregular patches on upper surface of leaves, with growth of the water mould (oomycete) below. Seedlings stunted or killed. Damage on flower heads of broccoli and cauliflower greater than on plants used for leaves, e.g., cabbage.
Spread in wind and rain, and trade in seedlings.
Cultural control: weed; water early in day; avoid overcrowding; crop rotation, collect and burn trash after harvest.
Chemical control: copper, chlorothalonil, mancozeb (protectants); or metalaxyl, phosphorous acid (systemic).

Common Name

Cabbage downy mildew

Scientific Name

Hyaloperonospora parasitica; previously known as Peronospora parasitica. There are different strains of the Oomycete such that the strain on radish does little damage to cabbage.

AUTHOR Grahame Jackson
Photo 1 Diseases of vegetable crops in Australia (2010). Editors, Denis Persley, Tony Cooke, Susan House. CSIRO Publishing. Photo 2 Kohler F, Pellegrin F, Jackson G, McKenzie E (1997) Diseases of cultivated crops in Pacific Island countries. South Pacific Commission. Pirie Printers Pty Limited, Canberra, Australia.

Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.

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