Diseases of Fruit Plantation Medicinal and Aromatic Crops

Grey blight

Causal organism: Pestalotia theae Sawada

• It occurs in North as well as South India. In South India, it is prevalent in Karnataka, Kerala and TamilNadu. Apart from India it has been reported from Java and Sri Lanka also.
Symptoms

• The disease appears as minute, brownish spots on older leaves which soon turn grey.
• The spots are mostly irregular and several of them may coalesce to form irregular grey patches. The spots have fine concentric lines.
• Fructifications of the fungus appear as black dots in older leaves on the upper surface.
• The fungus infects plucking points and causes die-back. Generally grey blight attacks older leaves of the tea plant.
• If young leaf is infected, the leaves are blackened and frequently the attack takes place even before the leaf is unfolded.
• It sometimes attacks the ends of plucked shoot and kills them back upto a short distance and repetition of this process results in production of a bush of dead shoots.
Epidemiology

• The incidence is more frequent on wet bushes, especially if it is deficient in potassium.
• The infection is also predisposed by sun scorch, insect puncture and plucking injuries.
• Mode of spread and survival
• The conidia are wind borne
Management

• Copper oxychloride (0.3%) or Bordeaux mixture (1.0 %) may be sprayed twice, once in cold weather and again in April or May to check the disease.