Pacific Pests, Pathogens & Weeds - Mini Fact Sheet Edition

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Tomato late blight (261)

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Photo 1. Rapid destruction of tomato plants by late blight, Phytophthora infestans.

Photo 2. Large irregular-shaped spots on the leaves, and rots on the fruit, of tomato caused by late blight, Phytophthora infestans.

Photo 3. Close-up of leaf spots caused by late blight, Phytophthora infestans.

Photo 4. Symptoms of late blight on potato, Phytophthora infestans.

Photo 5. Tomato trial uniformly attacked and destroyed by late blight, Phytophthora infestans.

Photo 6. Close-up of Photo 1 to show the destruction caused by late blight, Phytophthora infestans.

Summary

• Wordwide 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, dimethomorth or strobilurins. Phosphorus acid either alone or with chlorothalonil.

Common Name

Tomato late blight, potato late blight

Scientific Name

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