Anthracnose of Cucurbits

Causal Agent: Colletotrichum orbiculare is a fungal pathogen responsible for causing anthracnose in cucurbit crops. This disease affects a variety of cucurbits, including pumpkins, squashes, cucumbers, and melons.

Symptoms:

1. Leaf Lesions:

   • Circular Lesions: Anthracnose lesions on leaves are typically circular, with a dark brown to black color.
   • Concentric Rings: Lesions may develop concentric rings as they expand.
   • Target-Like Appearance: The lesions often give the leaves a target-like appearance.

2. Fruit Lesions:

   • Sunken Spots on Fruit: Anthracnose can cause sunken spots on the surface of fruit.
   • Color Changes: Infected areas may exhibit color changes, and the fruit can become distorted.

3. Vine Lesions:

   • Lesions on Vines: Stems and vines may also develop lesions, affecting the overall health of the plant.

4. Conidia Formation:

   • Conidia in Acervuli: The fungus produces conidia (asexual spores) in acervuli within the lesions.

Identification:

1. Circular Lesions: Circular, dark brown to black lesions on leaves, fruit, and stems.
2. Target-Like Appearance: Concentric rings that give the lesions a target-like appearance.

Conditions Favoring Disease:

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

Management:

1. Resistant Varieties:

   • Plant Resistant Cultivars: Choose cucumber or squash varieties that are resistant or tolerant to Colletotrichum orbiculare.

2. Cultural Practices:

   • Crop Rotation: Rotate cucurbit crops with non-host crops to reduce inoculum.
   • Sanitation: Remove and destroy infected plant material, including crop residues.
   • Proper Spacing: Ensure adequate spacing between plants for good air circulation.

3. Fungicides:

   • Protective Fungicides: Application of fungicides may be considered, especially during periods conducive to disease development.

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