- Worldwide distribution. On tomato, potato and wild species in the potato family. There is evidence of strains attacking different hosts. An important disease.
- A water mould, or oomycete, not a fungus.
- Irregular patches on leaves; white cottony growth with spores on undersides. Leaves yellow, shrivel and fall. Dark brown, firm fruit rot. Worse in cool, wet weather.
- Spread by wind or wind-driven rain, up to 20 km; and on seed for planting.
- Cultural control: check plants in nursery; avoid planting near older plants; space plants to aid air movement; intercrop; stake; mulch; drip rather than overhead irrigation; tolerant varieties; crop rotation.
- Chemical control: copper, mancozeb or chlorothalonil, alone, or alternate with, e.g., metalaxyl, cymoxanil, dimethomorph or strobilurins. Phosphorus acid either alone or with chlorothalonil.
Pacific Pests, Pathogens, Weeds & Pesticides
Tomato late blight (261)
Photo 2. Large irregular-shaped spots on the leaves, and rots on the fruit, of tomato caused by late blight, Phytophthora infestans.
Tomato late blight, potato late blight
AUTHOR Grahame Jackson
Information from CABI (2015) Phytophthora infestans (Phytophthora blight) Crop Protection Compendium. (https://www.cabi.org/cpc/datasheet/40970); and from Diseases of vegetable crops in Australia (2010). Editors, Denis Persley, et al. CSIRO Publishing.
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.