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

Stem end rot of mango

It is a destructive disease of mange and it is known to occur in India and other mango growing countries. In India it was first described during 1945. Since then it has been observed in Delhi, Rajasthan, U.P` and other states.

Symptoms

• The onset of die back becomes evident by discoloration and darkening of the bark some distance from the tip.
• The dark area advances and young, green twigs start withering first at the base and then extending outwards along the vines of the leaf edges.
• The affected leaf turn brown and its margin roll upward. At this stage, the twig or branches dies, shrivels and falls.
• This may be accompanied by exudation of the gum. Infected twig show external discoloration.
• Brown streaking of vascular tissues is seen on splitting the twigs lengthwise.
• The fungus also infects the fruits.
• Infected fruit pericarp darkens near the pedicel base. More portions of fruit turn black to soften.


Etiology

Diploidia natalensis (Pole Evans.)
The fungus produces brown to black, globouse to sub globose, pyriform, erumpent pycnidia that are ostiolate. Two types of conidia are produced within a pycnidium. Hyline and olive-brown. The former are thin walled and unicellular, while the later are thick walled and bicelled with 4-6 longitudinal striations.
Mode of spread and survival: the fungus persists in infected plant parts, which serve as source of inoculum.

Epidemiology

• Relative humidity above 80%, max. &min. temperature of 31.50 C &25.90 C respectively.
• Rains favor the disease development.
• Nutritionally deficient plants are heavily affected.
Management
• Plants with balanced fertilization resist the disease.
• The coating of stem with fungicidal paints immediately after harvest or packing of fruits directly in the cellophane bags the infections completely.
• Removal of infected pedicel during fruit ripening also helps in keeping the disease under control.