Anthracnose of Tomatoes

Pathogen: Colletotrichum coccodes is a fungal pathogen that causes anthracnose and black dot disease in potatoes (Solanum tuberosum) and other solanaceous crops.

Symptoms:

1. Anthracnose Symptoms:

   • Leaf Lesions: Circular lesions on leaves with dark margins and often a tan to gray center.
   • Stem and Petiole Lesions: Lesions may also occur on stems and petioles.
   • Reduced Photosynthesis: Severe anthracnose can lead to defoliation, affecting the plant's ability to photosynthesize.

2. Black Dot Disease Symptoms:

   • Black Spots on Tubers: Small, dark, and round lesions (black dots) on the surface of tubers.
   • Lesions May Coalesce: Lesions may coalesce, forming larger areas of dark discoloration on the tuber surface.
   • Reduced Marketability: Severe black dot disease can result in reduced marketability of harvested potatoes.

Identification:

1. Anthracnose Lesions:

   • Circular lesions on leaves, stems, and petioles with dark margins.
   • Tan to gray centers within the lesions.

2. Black Dot Disease Lesions:

   • Small, dark, and round lesions (black dots) on the surface of tubers.
   • Lesions may coalesce, forming larger dark areas.

Conditions Favoring Disease:

1. Warm and Humid Conditions: Colletotrichum coccodes thrives in warm and humid environments.
2. Rain or Irrigation: Moisture on leaves and tubers from rain or irrigation facilitates spore dispersal and infection.

Management:

1. Resistant Varieties:

   • Plant Resistant Cultivars: Choose potato varieties that exhibit resistance or tolerance to Colletotrichum coccodes.

2. Cultural Practices:

   • Crop Rotation: Rotate potato crops with non-host crops to reduce inoculum.
   • Sanitation: Remove and destroy infected plant material, including crop residues.

3. Fungicides:

   • Protective Fungicides: Application of fungicides during the growing season, especially during periods conducive to disease development.

4. Post-Harvest Practices:

   • Proper Storage: Store harvested potatoes in cool and dry conditions to minimize the development of black dot lesions.

Note: Integrated disease management, combining cultural practices, resistant varieties, and fungicides, is often the most effective approach.