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

Dieback of Mango

• Near base of the pedicel the affected area enlarges to form a circular, black patch, which under humid atmosphere extends rapidly and turns the whole fruit completely black within 2/3days. The pulp becomes brown and softer.
• This disease is prevalent in all mango-growing states in India. In U.P.30-40% of road this disease affects side and other plantation.
 
SYMPTOMS

• The disease is characterized by dying back of twigs from tip downwards particularly in older leaves.
• It is giving an appearance of scorching by fire followed by complete defoliation. Barks are discolored and darkened at certain distances from tip.
• Such dark patches are generally seen on young green twigs. When the dark lesion increase in size, dying of young twigs begin at the base affecting leaf mid ribs extending along the veins.
• The upper leaves use their healthy green color and gradually turn brown accompanied by upward rolling of leaf margin. In, advanced stage, such leaves shriveled, fall off in a month are more, leaving the shriveled twigs.
• Internal browning in the wood tissue is observed on the slitting along the long axis. Cracks appear on branches, which exude gum. In fruits, the pericarp darkens


Etiology

Botryodiploidia theobromae Pat.

• It is a Pycnidial fungi. Pycnidiospores are hyaline and thin walled, becoming thick walled, and dark brown and one septate.
• They have longitudinal striation and measures 20-30* 10-15micrometer with paraphyses upto50micrometer long.
Mode of spread and survival

• The fungus is a wound parasite. Dead twigs and bark of the trees harbor the fungus. The spores are spread through rain splashes.
Epidemiology

• High temperature during summer predisposes the trees to the disease.
• Relative humidity of about 80%, max. &min. temperature of 31.50 c and 25.90 c respectively and rains favour the disease development.
• It causes great damage and when mango grafts are kept in humid propagation shed.
Management
• Fruits should be harvested on clear dry days.
• Injuries should be avoided on fruits at all stages of handling.
• Care should be taken to prevent snapping off of the pedicel.
• Dipping of mangoes in 6% solution of borax at 430c for 3min. gives effective control. Carbendazim 0.1% or theophanate-methyl, 0.1% or chlorothalonyl 0.2% spraying in the field before harvesting gives effective control.