Tomato Blight

Tomato blight is a common disease that affects tomato plants, caused by various fungal pathogens. The two most common types of blight that affect tomatoes are Early Blight and Late Blight. Here's an overview of each:

1. Early Blight (Alternaria solani)

• Caused by: The fungus Alternaria solani.

• Symptoms:

  • Dark brown to black spots with concentric rings (resembling a target) on the lower leaves, which may eventually turn yellow and drop.

  • Lesions may also appear on stems and fruit.

  • Generally starts on older, lower leaves and progresses upward.

• Conditions Favouring Early Blight:

  • Warm, humid conditions (typically 24-29°C).

  • High humidity and leaf wetness.

  • Poor air circulation.

• Control Measures:

  • Crop rotation to prevent the build-up of the pathogen in the soil.

  • Pruning lower leaves to improve air circulation.

  • Mulching to reduce soil splashing on leaves.

  • Application of fungicides (like chlorothalonil or copper-based products) when conditions favour disease development.

2. Late Blight (Phytophthora infestans)

• Caused by: The oomycete pathogen Phytophthora infestans (not a true fungus but a water mold).

• Symptoms:

  • Large, irregularly shaped, water-soaked lesions on leaves that quickly turn brown to black, often with a white, fuzzy growth on the undersides of the leaves.

  • Stems can develop dark lesions that may girdle the plant.

  • Fruit can develop brown, firm, and greasy-looking spots.

• Conditions Favouring Late Blight:

  • Cool, wet conditions (typically below 24°C).

  • High humidity and prolonged leaf wetness.

• Control Measures:

  • Destroying infected plants to reduce the spread.

  • Avoiding overhead watering to minimize leaf wetness.

  • Using resistant tomato varieties if available.

  • Applying fungicides preventively (such as those containing copper or specific systemic fungicides) before symptoms appear.

General Prevention Tips for Tomato Blight:

• Choose Resistant Varieties: Planting resistant or tolerant tomato varieties can reduce the impact of blight.

• Proper Plant Spacing: Ensures good air circulation around plants to reduce humidity and leaf wetness.

• Watering Practices: Water at the base of the plant rather than overhead to prevent water from splashing onto leaves.

• Sanitation: Remove and destroy infected plant debris. Clean up garden beds at the end of the season to prevent overwintering of pathogens.

• Crop Rotation: Avoid planting tomatoes in the same spot year after year to prevent soil-borne pathogens from accumulating.

• Fungicides: Regularly apply fungicides, especially if you have had blight problems in the past or if conditions are favorable for the disease.

By taking preventive measures and promptly addressing early symptoms, you can manage and reduce the impact of tomato blight on your plants.