AVRDC International Cooperators'
Fact Sheet

Tomato Diseases


Early Blight
Alternaria solani

Found worldwide

 leaf lesions: concentric rings, chlorosis

 

Damage Symptoms

Small dark circular spots enlarge into larger lesions composed of concentric rings.

Elliptical lesions occur on the stems and petioles, which are drastically weakened at the site of the lesion.

Fruit rot (green or ripe). Large dark lesions develop in the calyx area or on the upper shoulder.


Conditions for Development

The pathogen can be seedborne; it also may persist in crop debris or on volunteer tomatoes and wild solanaceous plants.

The disease is favored by extended periods of leaf wetness from frequent rain, overhead irrigation, or dews. Stressed plants are more susceptible, e.g. when attacked by nematodes and also during fruiting. 

  

elliptical stem lesions

Elliptical stem lesions; blighted foliage
 

fruit symptoms

Dark, concentric rings develop on stem end of infected fruit

     

Control

Treat seeds with fungicides. Use disease-free transplants. Rotate crops. Avoid planting adjacent overlapping tomato crops. Some tolerant varieties are available. A fungicide spray program is often necessary; recommended fungicides include Bravo (chlorothalonil), Dithane (mancozeb) and Quadris (azoxystrobin).
 

Last updated: 2001. 
Information from: Vegetable Diseases: A Practical Guide. Lowell L. Black, AVRDC; and AVRDC International Cooperators's Guide on Suggested Cultural Practices for Tomato.
 

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