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Pacific Pests, Pathogens & Weeds - Mini Fact Sheet Edition

Tomato early blight (211)

Photo 1. Large brown spots of early blight, Alternaria solani, on tomato, showing characteristic rings or targets.

Photo 2. Leaf spot caused by early blight on tomato, Alternaria solani.

Photo 3. Characteristic rings or target structures on potato leaf caused by early leaf blight, Alternaria solani.

Photo 4. Early blight, Alternaria solani, on a tomato stem, showing elongated target spots.

Photo 5. Early blight, Alternaria solani, on tomato fruit, showing black spores masses.

Photo 6. Spots of early blight, Alternaria solani, on potato.

Photo 7. Spots of Alternaria solani on potato leaves leading to collapse and death as they expand and join together.

Photo 8. Collapse of potato plant due to infection of early blight, Alternaria solani.

Summary

Worldwide distribution. On tomato, and many others in the same family, including potato, capsicum, eggplant, and some wild hosts in the potato family. An important disease.
Brown spots on the older leaves with yellow margins, and dark brown rings. Leaves dry up and fall. Sunken spots on the fruit.
Wind and rain spread spores; survival in debris and seed.
Cultural control: 2-3-year rotation, avoid planting near old crops; save seed only from disease-free plants; remove “volunteers”, and weeds; check seedlings for disease; space plants (60-90cm); avoid overhead irrigation; ensure good nutrition; collect and burn debris after harvest; check for tolerant varieties.
Chemical control: protectants - copper, mancozeb, or chlorothalonil (protectants); or strobilurins (systemics).

Common Name

Early blight of tomato and potato, target spot

Scientific Name

Alternaria solani

AUTHOR Grahame Jackson
Information from Diseases of vegetable crops in Australia(2010). Editors, Denis Persley, Tony Cooke, Susan House. CSIRO Publishing. Photos 1,4-6 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. Photo 2 (taken by Eric McKenzie), and used in this fact sheet, appeared previously in McKenzie E (2013) Alternaria solani. PaDIL - (https://www.padil.gov.au). Photos 3,7&8 Jacquie (Wright) Kami, formerly Plant Pathologist, Secretariat of the Pacific Community.

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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