Disease management in mango

Mango is most at home in the lowland tropics and subtropics, with flowers and young fruits that are killed if temperatures fall below 5°C for more than a few hours. With a long production pedigree in the hot, humid tropics it is no surprise that mango foliage, flowers and fruit are at constant high risk from infection by a wide range of fungal, bacterial and even algal diseases.

Anthracnose, scab, stem end rot and bacterial spot are the main economic diseases of mango; anthracnose is the most widespread and damaging. Mango trees and orchards at risk from anthracnose require a full programme of pre-harvest fungicide spraying. Use of broad spectrum acting copper-containing fungicides will generally manage other less severe but still important fungal, bacterial and algal diseases.

Anthracnose of mango

In geographic distribution, disease severity and economic damage, Colletotrichum gloeosporioides (mango anthracnose) is the most important fungal pathogen. Anthracnose affects flowers, young fruits, leaves and twigs and appears later as a post-harvest/storage disease of fruit following the rejuvenation of latent infections of young fruit that occurred early in the season. Typical symptoms are black, slightly sunken lesions of irregular shape which enlarge to cause leaf spotting, blossom blight, fruit staining and fruit rot.

Leaf symptoms start as small, angular dark coloured spots and rapidly enlarge on young leaves to form extensive areas of necrotic and dead leaf tissue. Infections which begin on older leaves are restricted to spots 6mm in diameter appearing glossy dark brown and black on the mature, hardened leaves.

Symptoms on panicles (flower clusters) begin as small black or dark brown spots which enlarge, coalesce and kill flowers, with large irrecoverable losses in yield. Infections of fruit may proceed in the orchard to cause extensive decay of mangoes on the tree but are just as likely to remain dormant, springing into life later after picking, while the fruit is in storage and transit. The fungus penetrates the fruit skin and remains in a 'latent' condition (quiescent state) and shows no symptoms of disease until fruit ripening gets underway.

Physiological changes associated with ripening push the pathogen into an active state, producing prominent black spots that coalesce and penetrate deep into the flesh with extensive fruit rotting. An additional aspect of fruit damage...