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Diseases: Mango suffers from several diseases at all stages of its life. All the parts of the plant, namely, trunk, branch, twig, leaf, petiole, flower and fruit are attacked by a number of pathogens including fungi, bacteria and algae. They cause several kinds of rot, die back, anthracnose, scab, necrosis, blotch, spots, mildew, etc. Some of these diseases like powdery mildew are of great economic importance as they cause heavy losses in mango production. Major diseases of mango and their control measures are discussed below.

a) Powdery mildew: Powdery mildew is one of the most serious diseases of mango affecting almost all the varieties, It occurs up to latitude of 40^o North and South of the equator. It may persist for longer period at an elevation of 600-1200 meters, in many African countries, south of the Sahara, the middle East, Southern Asia and America : from the Southern United States to Peru and Brazil. The disease is reported to cause approximately 20 per cent crop loss in Maharashtra state alone. Sometimes, as high as 70-80 per cent crop loss has been recorded on individual plant basis.The characteristic symptom of the disease is the white superficial powdery fungal growth on leaves, stalks of panicles, flowers and young fruits. The affected flowers and fruits drop pre-maturely reducing the crop load considerably or might even preven the fruit set. Rains or mists accompanied by cooler nights during flowering are congenial for the disease spread. The fungus parasitizes young tissues of all parts of the inflorescence, leaves and fruits.

Control : Following three sprays of fungicides at 15 days interval recommended for effective control of the disease :

b) Anthracnose: The anthracnose disease is of widespread occurrence. The disease causes serious losses to young shoots, flowers and fruits under favourable climatic conditions of high humidity, frequent rains and a temperature of 24-32^oC. It is also affects fruits during storage. The disease produces leaf spot, blossom blight, withertip, twig blight and fruit rot symptoms. Tender shoots and foliage are easily affected which ultimately cause ‘die back’ of young branches. Older twigs may also be infected through wounds which in severe cases may be fatal.

Depending on the prevailing weather conditions blossom blight may vary in severity from slight to a heavy infection of the panicles. Black spots develop on panicles as well as on fruits. Severe infection destroys the entire inflorescence resulting in no setting of fruits. Young infected fruits develop black spots, shrivel and drop off. Fruits infected at mature stage carry the fungus into storage and cause considerable loss during storage, transit and marketing. The fungus perpetuates on twigs and leaves of mango or other hosts. Varietal differences in susceptibility have been noted in India. In Kerala, maximum damage was observed on Neelum, whereas variety Edward was reported to be resistant. Since the fungus has a long saprophytic survival ability on dead twigs, the diseased twigs should be pruned and burnt along with fallen leaves for reducing the inoculum potential.

Control: Trees may be sprayed twice with Bavistin (0.1%) at 15 days interval during flowering to control blossom infection. Spraying of copper fungicides (0.3%) is recommended for the control of foliar infection.

c) Die back: Die back is one of the serious diseases of mango. The disease on the tree may be noticed at any time of the year but it is most conspicuous during Oct.-Nov. The disease is characterized by drying of twigs and branches followed by complete defoliation, which gives the tree an appearance of scorching by fire. The onset of die back becomes evident by discolouration and darkening of the bark. The dark area advances and young green twigs start withering first at the base and then extending outwards along the veins of leaf edges. The affected leaf turns brown and its margins roll upwards. At this stage, the twig or branch dies, shrivels and falls. This may be accompanied by exudation of gum. In old branches, brown streaking of vascular tissue is seen on splitting it longitudinally. The areas of cambium and phloem show brown discolouration and yellow gum like substance is found in some of the cells.

Control : 1- Prune the diseased twigs and spray with copper oxychloride (0.3%) on infected trees. Pruning should be done in such a way that the twigs are removed 2-3 inches below the affected portion. 2- In small plants, pruning of twigs is followed by pasting of copper oxychloride.

d) Phoma blight: Phoma blight, a new disease of mango, was first reported at Central Mango Research Station, Lucknow. The disease was later detected in mango growing belt around Lucknow region. It is now gaining economic importance.

The symptoms of the disease are noticeable only on old leaves. Initially, the lesions are angular, minute, irregular, yellow to light brown, scattered over leaf lamina. As the lesions enlarge, their colour changes from brown to cinnamon and they become almost irregular. Fully developed spots are characterized by dark margins and dull grey necrotic centres. In case of severe infection such spots coalesce forming patches measuring 3.5-13 cm in size, resulting in complete withering and defoliation of infected leaves.
Control : The disease could be kept under control by spray of copper oxychloride (0.3%) just after the appearance of the disease and subsequent sprays at 20 day intervals.

e) Bacterial Canker: Canker disease of mango, caused by a bacterium,  is prevalent in Andhra Pradesh, Maharashtra, Karnataka, Kerala, Tamil Nadu, U.P., Bihar, Delhi, Haryana, Madhya Pradesh and probably in several other mango growing areas. Besides being pathogenic on several varieties of mango, the organism is capable of infecting wild mango, cashew nut and weeds as well. The disease causes fruit drop (10-70%), yield loss (10-85%) and storage rot (5-100%). Many commercial cultivars of mango including Langra, Dashehari, Amrapali, Mallika, and Totapuri are susceptible to this disease.
The disease is found on leaves, petioles, twigs, branches and fruits, initially producing water-soaked lesions and later turning into typical cankers. The disease first appears as minute water-soaked irregular lesions on any part of leaf or leaf lamina. The lesions are light yellow in colour but with age, enlarge and turn dark brown to black. They become angular, cankerous and raised, and are surrounded by chlorotic halos. Several lesions coalesce to form irregular necrotic cankerous patches. In severe infections the leaves turn yellow and drop off. Cankerous lesions appear on petioles, twigs and young fruits. The water soaked lesions also develop on fruits which later turn dark brown to black. They often burst open, releasing a highly contagious gummy ooze containg bacterial cells. The fresh lesions on branches and twigs are water soaked which later become raised and dark brown in colour with longitudinal cracks but without any ooze.
Control : 1-Seedling certification, inspection and orchard sanitation. 2-Three sprays of streptocycline (100 ppm) or Agrimycin-100 (100 ppm) after first visual symptom at 10-days intervals. 3-Monthly sprays of Bavistin (1000 ppm) or copper oxychloride (3000 ppm) were also found effective.

Precautions: Do not wait for appearance of the disease. The key to success for full control is to start application of fungicides before the infection has established.
 

f) Red rust: Red rust disease, caused by an alga, has been observed in mango growing areas. The algal attack causes reduction in photosynthetic activity and defoliation of leaves thereby lowering vitality of the host plant.
The disease can easily be recognized by the rusty red spots mainly on leaves and sometimes on petioles and bark of young twigs and is epiphytic in nature. The spots are greenish grey in colour and velvety in texture. Later, they turn reddish brown. The circular and slightly elevated spots sometimes coalesce to form larger and irregular spots.
The disease is more common in closely planted orchards. Fruiting bodies of the alga are formed in humid atmosphere. The zoospores formed by the sporangia initiate fresh infections. Stem entry is achieved by way of cracks. The affected areas crack and scale off. In severe infection the bark becomes thickened, twigs get enlarged but remain stunted and the foliage becomes sparse and finally dries up.

Control : Two to three sprays of copper oxychloride (0.3%) is effective in controlling the disease.
 

g) Sooty mould: The disease is common in the orchards where mealy bug, scale insect and hopper are not controlled efficiently. The disease in the field is recognis by the presence of a black velvety coating, i.e., sooty mould on the leaf surface. In severe cases the trees turn completely black due to the presence of mould over the entire surface of twigs and leaves. The severity of infection depends on the honey dew secretion by the above said insects. Honey dew secretions from insects sticks to the leaf surface and provide necessary medium for fungal growth. The fungus is essentially saprophytic and is non-pathogenic because it does not derive nutrients from the host tissues. Although no direct damage is caused by the fungus, the photosynthetic activity of the leaf is adversely affected due to blockage of stomata.
Control: 1-Pruning of affected branches and their prompt destruction prevents the spread of the disease. 2-Spraying of 2 per cent starch is found effective. 3-It could also be controlled by spray of Nottasul + Metacin + gumacasea (0.2% + 0.1% + 0.3%).                                      

B. Postharvest Diseases: The mango fruit is susceptible tomany postharvest diseases caused by anthracnose (C. gloeosporioides) and stem end rot (L. theobromae) during storage under ambient condtions or even at low temperature. Aspergillus rot is another postharvest disease of mango.

Control: Preharvest sprays of fungicides could control the diseases caused by latents infection of these fungi. Postharvest dip treatment of fruits with fungicides could also control the diseases during storage. The following treatments are suggested.

1- Three sprays of carbendazim (0.1%) orthiophante-methyl (0.1%) at 15 days interval should be done in such a way that the last spray falls 15 days prior to harvest. 2- Postharvest dip treatment of fruits in carbendazim (0.1%) in hot water at 52+1^oC for 15 minutes.

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