Anthracnose of Avocados

Causal Agent: Anthracnose of avocados is commonly caused by Colletotrichum gloeosporioides, a fungal pathogen. This disease can affect various parts of the avocado tree, including the fruit, leaves, and twigs.

Symptoms:

1. Fruit Lesions:

   • Circular Lesions: Anthracnose lesions on avocados are often circular and may vary in size.
   • Sunken Spots: Lesions are sunken and may have a dark center.
   • Color Changes: Initially, lesions may appear water-soaked and later turn tan to dark brown.

2. Leaf Symptoms:

   • Lesions on Leaves: Infected leaves may develop lesions with irregular margins.
   • Leaf Drop: Severely infected leaves may drop prematurely.

3. Twig and Stem Lesions:

   • Lesions on Twigs: Twigs and stems can also develop lesions, affecting the overall health of the tree.

4. Fruit Rot:

   • Rotting of Fruit: In advanced stages, the entire fruit may rot, making it unsuitable for consumption.

5. Spore Production:

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

Identification:

1. Circular Lesions: Circular, sunken lesions on fruit, leaves, and twigs.
2. Dark Centers: Lesions often have a dark center as they mature.

Conditions Favoring Disease:

1. Warm and Humid Conditions: Anthracnose thrives in warm and humid environments, and disease incidence is higher under such conditions.
2. Rain or Irrigation: Moisture on leaves and fruit from rain or irrigation facilitates spore dispersal and infection.

Management:

1. Fungicides:

   • Protective Fungicides: Regular application of fungicides during periods conducive to disease development.
   • Cultural Practices: Properly time fungicide applications based on the avocado tree's growth stage and weather conditions.

2. Cultural Practices:

   • Sanitation: Remove and destroy infected plant material to reduce inoculum.
   • Pruning: Prune and thin the tree to improve air circulation.
   • Avoid Overhead Irrigation: Minimize prolonged leaf wetness by using drip or furrow irrigation.

3. Resistant Varieties:

   • Plant Resistant Cultivars: If available, consider planting avocado varieties that show resistance or tolerance to anthracnose.

4. Post-Harvest Practices:

   • Proper Storage: If applicable, store harvested avocados in cool and dry conditions to prevent post-harvest anthracnose development.

Note: Integrated disease management, combining chemical control with cultural practices, is often the most effective approach.