Lettuce downy mildew (209)
Pacific Pests, Pathogens and Weeds
- Worldwide distribution. Temperate and sub-tropical countries. On lettuce and relatives in daisy family, and weeds. An important disease.
- Round to angular spots, light green to yellow, merging and turning brown, sometime soft and slimy. Spores on the underside.
- Spread is by spores in wind over long distances.
- Cultural control: in nursery – avoid overcrowding; in field - avoid overlapping crops; 2-3-year rotation; spacing; drip irrigation; weed; collect trash and burn after harvest.
- Chemical control: copper, mancozeb, or chlorothalonil (protectants); or metalaxyl (systemic) with mancozeb (or alternating with mancozeb).
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