Besides powdery mildew, anthracnose, caused by the fungus Colletotrichum gloeosporioides, is undoubtedly the most common and widespread fungus disease of mango and is a major factor limiting production in areas where conditions of high humidity prevail. The fungus invades inflorescences, fruits, leaves and twigs. Substantial losses due to this disease are recorded every year not only at premature stages of the crop but also during storage after picking.
Humidity, rains and heavy dew during critical infection periods greatly increase the disease incidence. Most infections occur from the beginning of flowering in gradually decreasing severity until the fruit is about half-grown. Infections on the flower and panicle a loosely branched inflorescence appear first as minute brown or black spots which slowly enlarge. Infected flowers usually wither and die before fruit set.
Young fruits are readily infected. Spots may remain as pinpoint latent dormant infections or they may enlarge in wet weather. Wet weather also causes characteristic tear-stain symptoms due to the spread of fungal spores by raindrops. The latent infections on young fruits cause much of the decay which occurs in mature fruits. Nearly mature to ripe fruits will have black spots of varied form which may be slightly sunken and show surface cracks penetrating deeply into the fruit causing extensive rotting or complete blackening of the fruit surface.
To control untreated subjects used for comparison with those given a particular treatment the disease, orchard sanitation and pruning of dead twigs and branches—which may harbour the fungus—are the principal control measures used to reduce the source of a new infection cycle. The widespread occurrence of the inoculum of the fungus makes it impossible to control the disease by pruning and the removal of dropped leaves alone. To be more successful, the above mentioned measures have to be supplemented by spray applications using Mancozeb, copper oxychloride, Maneb, Propineb, Benomyl etc.
It is recommended to start spraying at the stage of flower-bud formation. During flowering/fruit set and until the fruits have developed to half their size, spraying should take place at fortnightly intervals. After this, it is sufficient to treat the trees once a month. It is very important to apply a full cover spray for the first two applications. Since this period is also the critical stage during which powdery mildew and the mango weevil attack, counteractions should be implemented using recommended fungicide chemical to control plant diseases/insecticide chemical to control crop pests combinations.
All cultivars are to some extent susceptible not resistant to anthracnose. The range of resistance (with Tommy Atkins being the most resistant) is: Tommy Atkins, van Dyke, Sabine, Ngowe, Gesine, Apple, Keitt, Kent, Kensington, Chino, Sensation, Batawi, Boribo, Haden, Maya.
There are several other diseases of mango fruits that have been reported occasionally. These include alternaria rot, mango scab, stem-end rot, algal leaf spot and sooty mould.