MANGO, MANGIFERA indica L. an important foreign currency earning fruit crop of Pakistan. It is known as the “king of fruits”. The mango is nutritionally rich in carbohydrates and vitamin A and C. It is relished and liked by everyone for its flavour, dietetic and medicinal value.

In Pakistan, mango is grown over an area of 94,100 ha while its production is 916,800 tons. In Sindh it is grown on 43,500 ha, yeilding 320,700 ton, which is about 46.2 and 34.9 per cent of total area and production respectively. According to the Export Promotion Bureau, Pakistan has exported 47,601,678 and 31,000kg of fresh and dried (anchor) mangoes with a value of $11,589.6 and $21,300, respectively during July-June 1999-00 to Dubai, Saudi Arabia, the UK, Germany, France, Holland, Switzerland, Italy, Singapore and Malaysia.

Pakistan offers more than 100 mango varieties famous among which are sindhri, dusehri, summer behisht chaunsa, anwar ratole and langra. These differ in characters, viz taste, flavour, colour, tinges, shape and size and determines its quality and market value at home and abroad. At present, one late season, five mid seasons and six early seasons (total 12) mango varieties are cultivated commercially in Sindh. These verities were released from 1949 to 1967, with yield potential of 8,000 to 21,600kg/ha (Table).

The present situation of mango orchards in reference to Sindh needs special attention where trees are dying due to an unknown disease. Badly declining mango trees speak of the unknown disease. It is usually caused by living organisms called pathogen, such as fungus, bacterium, nematode and insect pest and are regarded as infectious. Some other factors like physiological disorders or change in environmental conditions cause non-infectious diseases, the reasons for which are low or high temperature, unfavourable oxygen and soil-moisture relations, injurious atmospheric gases or chemical injury, lightening injury and deficiencies or excesses of nutrients. The viruses are sometimes considered living and sometimes non-living. Plant disease caused by viruses are regarded as infectious or non-infectious disease. Change in environmental conditions due to global warming and the green house effects result in low rainfall, high CO2, air and water pollution, soil degradation, land erosion, salinity, waterlogging and desertification, all of which directly hit the crop.

An injury or abnormality brought about by insects is entomology and the remaining deviations plant pathology. Crop protection is mother discipline of entomology and the plant pathology is concerned with the health and productivity of the growing plants. The disease losses are hazards but can be minimized through research. To evaluate and solve new disease problems and to work out practicable procedures, which growers can adapt, is the role of the crop protection.

Mango diseases: Mango is known to suffer from a number of diseases caused by different organisms affecting different parts at all stages of growth. Powdery mildew sooty mould, fruit rot, leaf blight, anthracnose, stem blight or die back, and root rot are recorded as fungal diseases; bacterial leaf spot; and malformation of mango inflorescence (the actual cause is still not confirmed) are reported from Pakistan. No information regarding the extent of damage to the plant is available, but some of these are certainly responsible for causing considerable damage to mango crop.

Malformation is very common and widely distributed in orchards all over the country. Compact leaves are formed at the apex of the shoot or in the leaf axil, to form the bunchy top seedlings and are usually shallow with few tertiary roots.

The tap root may be twisted and may show necrosis. Sometimes, small leaves appear as shootlets, growth of which is checked and several similar shootlets arise from the axil of the scaly leaves and form bunches, which are thicker than the main stem.

Floral aggregation (malformation) may also appear on shortened primary axil of the inflorescence, which is further branched to secondary and tertiary branches, on which flowers are borne in clusters and no fruit setting is observed. Infected inflorescence remains green for long time, no malformed heads dry up in black masses but persist on trees. The symptoms are persistent in almost all those gardens in which pruning has not yet been done.

Anthracnose is prevalent in almost all parts of the country. The leaves, petioles, twigs and fruits are attacked. Appearance of oval and irregular blister-like brown spots develop on the tips, margins and centre of leaves and twigs. Blackening of petioles, elongated necrotic streaks on young twigs and branches are observed, and leaves drop down from top to bottom. Drying and rupturing of affected tissues, drying and falling of leaves, brightening of blossoms, staining and rotting of fruits are also main symptoms of anthracnose.

Stem blight or die back become evident by discolouration and darkening of the bark, withering of leaf tips and shedding of leaves, the twigs die back from top to bottom. The exudation of gum from infected portion is also one of the major evident of this disease. Brown streaks are observed on vascular tissues by lengthwise splitting of the diseased twigs. Almost all mango varieties are reported as susceptible to this disease.

Root rot is also prevalent in almost all orchards, manifest itself as withering and drying of the plant from top to bottom and the whole plant die down. Initially, rootlets are affected and are rotten, later on the smaller, tertiary roots and ultimately the bigger, secondary and primary main roots are infected which results in gradual decline of the plant and the plant dies. The uptake of nutrients and water is blocked due to the rotting of the roots, which results in drying up of the plants.

Present situation: It is clear from the symptoms of anthracnose, stem blight or die back and root rot that the present problem is not because of any one disease. Perhaps, the complicated case emerge due to the combine attack of anthracnose, stem blight or die back, root rot, leaf blight, bacterial leaf spot and malformation diseases, which are responsible for the dying of trees.

That may also be proved through nature and the behaviour of these disease-causing organisms. High temperature, high relative humidity and weak plants are main contributing factors in the spread of anthracnose and die back, while root rot is caused by fusarium species which develop more on weak plants, in high soil temperature and drought conditions. It is also true that the dying of trees or the decline is generally observed more in the neglected orchards, which is a common factor. Present shortage of irrigation water is another reason which helps the disease causing organisms to grow, develop and spread.

Almost all commercial mango varieties are old. It is a question that how such varieties, after long period, could be resistant to the disease? More or less, all varieties are reported to be susceptible, to most of the above discussed diseases. Now it is up to the researchers what they would like to do for the identification of actual problem, how they control the existing or complicated diseases.

Conclusion and suggestion: It is concluded that the problem is not because of any one disease, but mango decline is the outcome of combine attack of anthracnose, stem blight or die back, root rot, leaf blight, bacterial leaf spot and malformation diseases, involving several different fungi. Therefore, it is suggested that integrated disease management principles must be applied by using different fungicides in combination with suitable insecticides. Various cultural practices may also be helpful in checking the diseases. Fungicides increase the cost of production and its use is risky for the health of the workers. It decreases the fruit quality because of toxic substance residue, that may remain present so much time in the fruit. Therefore, following integrated disease management principles should be applied. The researchers are requested to plan their future strategies for the benefit of the nation and the country.

*Only healthy seeds, seedlings and plants should be used for planting and budding or grafting.

*Irrigation must be applied as per requirement, but not subject to the availability.

*Avoid high doses of nitrogen fertilizers, but apply proper and balanced fertilizers, on the basis of soil type, age and the need of the tree.

*Proper sanitation of orchards and pruning of trees may help in reducing the infection and its growth, development and further spread of the disease causing fungus or so.

*Easily available broad spectrum fungicides should be used, in combination with the insecticides at proper dose.

*Modern mango production technology must be adopted as per recommendations of researchers. The encouraging results could be obtained with consulting the pathologist and the entomologist.

Table: Mango varieties, year of release and yield potential (kg/ha.)