Diseases of Fruit Plantation Medicinal and Aromatic Crops

Grey leaf blight

Causal organism: Pestalotia palmarum
Leaf spot disease is caused by Pestalotia palmarum which is widesperead in the major coconut growing countries. The incidence of the disease is usually influenced by the nutrient• status of the soil and the palm as well. Young palms are mostly susceptible when the soil is deficient in potash and rich in nitrogen content.
Symptoms
Leaf spot symptoms develop only on the mature leaves in the form of small yellowish-brown spots on the leaflets which gradually become oval in shape with a greyish band. In advance stage, the infected portion of the leaflets shows a burnt or blighted appearance.



Etiology

• Septate mycelia.
• Asexual fruiting body: Conidia borne in acervulus.
• Sexual fruiting body: Perithecia.
• Source of inoculum
• Primary source of inoculums: Dormant mycelia
• Secondary source of inoculums: Air borne conidia

Management

• Removal of the older infected leaves and spraying the foliage with
• Improvement in drainage system and adequate application of potassic fertilizers are very essential to suppress the disease.
  
• Spraying 1% Bordeaux mixture during pre-monsoon period is beneficial.