Apple scab

Pathogen: Venturia inaequalis is a fungal pathogen responsible for causing apple scab, a common and damaging disease affecting apple trees (Malus domestica).

Symptoms:

1. Leaf Lesions:

   • Olive Green to Dark Brown Spots: Circular to irregularly shaped lesions on leaves with colors ranging from olive green to dark brown.
   • Velvety Appearance: Lesions may have a velvety or scaly appearance.

2. Fruit Lesions:

   • Scab-Like Spots: Similar lesions may appear on the surface of apples, resembling scabs.
   • Distorted and Cracked Fruits: Severely infected fruits may become distorted, cracked, and unmarketable.

3. Twig and Fruit Stem Lesions:

   • Lesions on Twigs and Fruit Stems: Twigs and fruit stems can also develop scab-like lesions.

4. Reduced Photosynthesis:

   • Premature Leaf Drop: Severe infections can lead to premature leaf drop, affecting the tree's ability to photosynthesize.

Identification:

1. Leaf Lesions:

   • Circular to irregular lesions with an olive green to dark brown color.
   • Velvety or scaly appearance on the lesions.

2. Fruit Lesions:

   • Scab-like spots on the surface of apples.
   • Distorted and cracked fruits in severe cases.

Conditions Favoring Disease:

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

Management:

1. Resistant Varieties:

   • Plant Resistant Cultivars: Choose apple varieties that exhibit resistance or tolerance to Venturia inaequalis.

2. Cultural Practices:

   • Leaf Removal: Remove and destroy infected leaves to reduce inoculum.
   • Proper Pruning: Prune trees to improve air circulation and reduce humidity within the canopy.
   • Sanitation: Remove and destroy fallen leaves to minimize overwintering spores.

3. Fungicides:

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

4. Post-Harvest Practices:

   • Proper Storage: Store harvested apples in cool and dry conditions to minimize the development of scab lesions.

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