MANGO, the king of fruits, is well adapted to the country’s soil and climatic conditions and Pakistan stands fifth among the mango growing nations. In 2007, mango orchards occupied over 93,000 hectares that produced 9,15,000 tons of fruit.

The mango varieties include Langra, Dusehri, Samar Behisht, Chaunsa, Anwar Ratol which are grown in Punjab. Sindhri, Bagan Phali, Suwarneka, Neelum and Gulab Khas are the famous Sindh varieties.

Mango suffers from a number of diseases at various stages of its development. All plant parts — trunk, branch, twig, leaf, petiole, flower and fruit — are attacked by different pathogens. Some of the diseases such as malformation, anthracnose, powdery mildew, Verticillium wilt, stem-end rot, red rust, fruit rot, leaf blight and stem blight severely limit mango production.

There are various causative organisms of these diseases. Among them fungi is the most serious. Bacteria, algae, angiospermic parasites and nutritional deficiencies are other causative agents. Some of the diseases that cause severe harm to mango are:

Malformation: Malformation is one of the most damaging diseases in the sub-continent. The disease affects vegetative and floral tissues of trees. Apical or auxillary buds produce shoots with shortened internodes and dwarfed leaves which are brittle and re-curve towards the supporting stem. Shoots may not expand fully, resulting in a bunched appearance on these portions of the plant.

More important, however, is the affect of malformation on fruit set: fruit in affected panicles either do not set or abort. Primary and secondary axes on affected panicles are shortened, thickened and greatly branched. Malformed panicles may produce as many as three times the normal number of flowers, and these are usually enlarged. Inflorescences may also have an increased proportion of male vs. perfect flowers and may produce dwarfed and distorted leaves.

Mango bud mite is believed to be a vector of this pathogen which enhances infection by wounding host tissues while feeding on mango. The pathogen is spread by grafting and in infected nursery stock. No effective fungicide has so far been produced to control this disease. Primary emphases should be on using pathogen-free propagation materials when new orchards are set up. If the disease is present in an orchard, all symptomatic tissues including the subtending three nodes should be removed from the orchard and burnt.

Anthracnose:Anthracnose is caused by fungus Colletotrichum gleosporioides. Flower blight, fruit rot, and leaf spots are among the symptoms of this disease.

Small black or dark-brown spots on the panicles (flower clusters) are the symptom of the disease. These can enlarge, coalesce and kill the flowers. On leaves anthracnose lesions start as small, angular, and brown to black spots. If tissue is young when infected, spots can enlarge to form extensive dead areas. Lesions that begin in older leaves are smaller with a maximum diameter of half inch; they appear as glossy dark brown to black angular spots.

The infection commonly occurs in fruits and may result in their decay. The fungus invades the skin of the fruit and remains in a dormant state till the fruit starts ripening. Ripe fruit, either before or after picking, can develop dark-brown to black spots leading to its decay.

Anthracnose usually assumes serious proportion in years when rain and heavy dews are frequent from the onset of flowering until fruits are about half the size.

Anthracnose can be controlled with fungicide application. Effective control of the post-harvest phase of the disease is best accomplished by a good spray programme in the orchard. Fungicide should be applied at the first appearance of panicles which should continue at intervals until the pre-harvest waiting period is reached.

Powdery mildew: Powdery mildew is a somewhat sporadic disease which can cause severe crop losses due to flower and panicle infection and subsequent failure of fruit set.

The powdery mildew appears from January to March. The disease can be diagnosed by the appearance of a whitish, powdery growth of the fungus on panicles and young fruit. Young infected fruit turns brown and fall. The white growth can also be seen on the undersurface of young infected leaves. Severe infection of young leaves results in premature leaf drop. On mature leaves, the spots turn purplish brown, as the white fungal mass eventually disappears. Powdery mildew occurs in the spring and is particularly destructive in years when the weather is cool and dry.

This disease can be controlled by fungicide. Dusting of fine sulphur can also be effective.

Verticillium wilt: Verticillium wilt is caused by soil-borne fungus Verticillium albo-atrum or V. dahliae. It is a disease of serious concern for mango growers. The problem is observed in young trees planted on land previously used for growing vegetables. The fungus can survive in soil in a dormant state over 15 years. When trees are planted in infested soil, the fungus invades through roots. As Verticillium colonises and blocks the vascular (water-conducting) system, trees start suffering from water stress and gradually die. If longitudinal cuts are made in infected branches, brown vascular discoloration is often evident.

The only practical control of this disease is possible by avoiding agricultural land with a previous history of vegetable production. Management of Verticillium wilt through site selection is becoming difficult in areas of increasing urbanisation.

Mango decline: Different diseases of mango, including blight, canker, gummosis, twig blight, tip die-back and stem bleeding, are listed here under the general term decline. Although these diseases are caused by several different fungi, they are all capable of causing all or some of the following symptoms: marginal scorching of leaf lamina which may or may not progress to defoliation; foliar symptoms of nutritional deficiencies -particularly of iron and manganese; dieback of small branches basipetally from the terminal (Fig.); oozing of a clear or cloudy exudates, either from terminal buds or from branches, scaffold limbs or trunks; and vascular discoloration.

The internal location and diversity of fungi that are involved in the decline syndrome reduce the opportunities for controlling these disorders with fungicides. These problems are usually observed after trees are affected by cold weather, drought, poor fertility and other stress factors. Thus, management of the controllable predisposing factors is beneficial.

For effective control of the disease, pruning and destruction of infected twigs is the best practice. Spraying the trees periodically with copper oxychloride sulphate can be helpful. Some times short hole-borers also predispose the trees to infection and hence proper insecticides are also to be sprayed. Healthy twigs should be selected for grafting of seedling during propagation.

Stem-end Rot: This is usually a post-harvest disease of the fruit. In general, the stem-ends of affected fruit appear dark brown and water soaked, and the affected areas may extend internally well into the fruit. Post-harvest treatment of fruit with hot water or fungicides can reduce the development of this disease.

Red rust: A parasitic algae incites this relatively minor disease of mango. Leaf spots start as circular green-gray areas that eventually turn rust red as the alga produces a profusion of rust-colored microscopic spores on the leaf surface. Infection of stem tissue can also occur and is much more serious than leaf infection. Cankers develop in the bark and stem-thickening can take place at infection sites. Rust-red “spore” masses will also develop on infected stems. Severely diseased branches may have to be pruned from the tree.

Alga spot only becomes a serious problem when growers are overly dependent on organic fungicides for general foliar disease control. It normally is not a problem where copper fungicides are used periodically.

To check these diseases and to enhance mango production, there is a need to develop improved nursery systems with high quality disease-free planting material; develop improved tree husbandry for production of high quality fruit; improve detection and management strategies for the sudden death syndrome and such other diseases and build capacity in mango industries to conduct integrated and targeted research, development and extension programmes.