Diseases of fruit plantation medicinal and aromatic crops (2+1)

Fruit canker

Causal organism: Pestalotiopsis psidii
Symptoms

• Infection generally occurs on green fruits.
• Minute, brown or rust- coloured, unbroken, circular, scabby lesions of 2 to 4 mm dia appear on the fruit which later tear the epidermis open in a circinate manner.
• The scab disfigures the fruits and their market value highly reduced.

Sources of inoculum

• Primary source of inoculum: Dormant mycelia. Helopeltis antonii, a kajji bug which punctures the young fruit for sucking its juice but the damages exposes the fruit to infection by the pathogen.
• Secondary source of inoculum: Air borne conidia
• Mode of spread: spread is through the wind-borne conidia.

Etiology

• The fungus is capable of growing at temperature between 20 and 25°C.
• Mycelial growth with intensive sporulation takes place at 5.5°C.
• Wounding results in quick attack by the fungus.

Management

• Since the wound created by insect predisposes the fruit to infection, spray young fruits after pollination with a suitable systemic insecticide (Dimethoate – 2ml/l) to prevent infection.
• Spread of the disease can be checked by three or four spraying with Bordeaux mixture1.0 percent or copper oxy chloride 0.2 per center.
• Summer irrigationand balanced nutritional management reduces the disease.