Fungal Disease in Tomato and Potato Plants

Early Blight

Early blight is a fungal disease that affects tomato and potato plants, leading to significant crop losses if not properly managed. This disease is caused by a fungus called Alternaria solani. It can also affect other solanaceous crops like eggplant and capsicum.

Disease Cycle

The fungus survives the winter by infecting plant materials in the soil or solanaceous weeds. During cool and moist conditions, the fungus produces numerous spores. These spores are carried by wind or water to nearby plants, initiating new infections. The disease can infect any part of the crop, with older leaves and stressed plants being more vulnerable. The spores enter the plant tissues through direct penetration or through damaged areas.

Infection and Symptoms

Contrary to its name, “early blight,” symptoms typically appear on older leaves towards the end of the growing season. The disease manifests as brown lesions on older leaves, which become dry and papery. As the infection progresses, these lesions develop characteristic concentric rings of raised and necrotic tissue. Infected leaves turn chlorotic and then necrotic, potentially leading to defoliation.

On stems, the disease starts as small, dark, and slightly sunken regions that enlarge over time. Concentric rings may also develop on the stems. Infected tubers exhibit dark sunken lesions, often surrounded by a raised purple-like margin.

The tuber tissue becomes dry, brown, and leathery, and the infection can continue even during storage, causing the tubers to shrivel. Infected fruits develop leathery lesions with possible concentric rings. As the infection progresses, these lesions may be covered with a mass of black fungal growth.

Management and Control

Chemical Control

One method of controlling early blight is through the use of fungicides. The following fungicides have proven effective against this disease:

  • CADILAC 800WP: Mix 50g with 20l of water for preventive purposes.
  • DISCOVERY 400SC: Mix 10ml with 20l of water.
  • EXEMPO CURVE 250SC: Mix 15ml with 20l of water.
  • FORTRESS GOLD 720WP: Mix 40g with 20l of water.
  • KATERINA 720SC: Mix 40ml with 20l of water.
    And several others (refer to the original list).


When conducting foliar sprays, it is recommended to mix the fungicide with INTEGRA at a ratio of 3ml/20l to improve its efficacy. Alternating between different fungicides can help prevent the pathogen from developing resistance. Timely application of fungicides is crucial.

Other Management Practices

In addition to chemical control, there are other practices that can help manage early blight:

  • Field sanitation: Remove infected plant materials to reduce the spread of the disease.
  • Crop rotation: Rotate with non-host crops to disrupt the disease cycle.
  • Use resistant varieties: Plant varieties that are resistant to early blight.
  • Avoid overhead irrigation: Wet foliage promotes rapid disease spread, so opt for alternative irrigation methods.
  • Proper weed control: Weeds can harbor the disease-causing pathogens, so ensure effective weed management.
  • Harvest precautions: Harvest tubers when the soil is dry to avoid wet conditions, and handle them carefully to prevent injuries.
  • Plant certified or disease-free seeds: Start with healthy seeds to reduce the risk of introducing the disease.


Early blight is a fungal disease caused by Alternaria solani that affects tomato and potato plants, among other solanaceous crops. Understanding the disease cycle, recognizing the symptoms, and implementing effective management practices can help minimize the impact of early blight and protect crop yields.

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