Ascochyta blight, black spot

Pathogen: Ascochyta pisi is a fungal pathogen responsible for causing Ascochyta blight, a common and destructive disease in pea crops (Pisum sativum).

Symptoms:

1. Leaf Lesions:

   • Circular Lesions: Circular to angular lesions on pea leaves, initially small and water-soaked.
   • Dark Borders: Lesions develop dark borders with a tan to gray center.
   • Leaf Blighting: Severe infections lead to the blighting and death of entire leaves.

2. Stem Lesions:

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

3. Pod Lesions:

   • Lesions on Pods: Pods can also become infected, leading to dark lesions and reduced pod quality.
   • Seed Infection: Seeds within infected pods may become discolored or shriveled.

Identification:

1. Circular Lesions:

   • Circular to angular lesions with dark borders and a tan to gray center on leaves and stems.

2. Pod Lesions:

   • Dark lesions on infected pods, impacting pod quality.

Conditions Favoring Disease:

1. Humid Conditions: Ascochyta blight thrives in humid environments.
2. Rain or Irrigation: Moisture on leaves and pods from rain or irrigation facilitates spore dispersal and infection.

Management:

1. Resistant Varieties:

   • Plant Resistant Cultivars: Choose pea varieties that exhibit resistance or tolerance to Ascochyta pisi.

2. Cultural Practices:

   • Crop Rotation: Rotate pea 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:

   • Seed Treatment: Treat pea seeds with fungicides to reduce the potential for seedborne infection.

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