Black tip (Koeli) of mango and its management

RC Shakywar, KS Tomar, M Pathak *

Black tip

Black tip or taper tip or girdle or tip rot or mango necrosis, locally known as koeli or koel padda or chimney disease of mango (Mangifera indica L.) is peculiar to India and does not occur in any other country. Woodhouse (1909) first reported it from Bihar in the year 1908.

It is the most common disease of mango fruits in Bihar, Uttar Pradesh and also occurs in Haryana, Madhya Pradesh, Punjab and West Bengal in orchards situated near to brick kilns and may bear the necrotic lesions and become useless for sale and consumption. Losses due to this disease are about 25%. In some trees there are almost 100% losses due to this disease. South India appears to be free from this disease of mango.

Some of the best mango varieties are highly susceptible i.e. Dasheri. India ranks first among world’s mango producing countries accounting for about 50% of the world’s mango production. Other major mango producing countries include China, Thailand, Mexico, Pakistan, Philippines, Indonesia, Brazil, Nigeria and Egypt.

India’s share is around 52% of world production i.e, 12 million tons as against world’s production of 23 million tons (2002-03). An increasing trend has been observed in world mango production averaging 22 million metric tons per year. World wide production is mostly concentrated in Asia, accounting for 75% followed by South and Northern America with about 10% share.

Economic Importance of Mango

The fruit is very popular with the masses due to its wide range of adaptability, high nutritive value, richness in variety, delicious taste and excellent flavor. It is a rich source of vitamin A and C. The fruit is consumed raw or ripe. Good mango varieties contain 20% of total soluble sugars. The acid content of ripe desert fruit varies from 0.2 to 0.5% and protein content is about 1%.

Raw fruits of local varieties of mango trees are used for preparing various traditional products like raw slices in amchur, brine, chutney, murabba, panhe (Sharabat) and pickle etc. Presently, the raw fruit of local varieties of mango are used for preparing pickle and raw slices in brine on commercial scale while fruits of Alphonso variety are used for squash in coastal western zone.

The wood is used as timber and dried twigs are used for religious purposes (Havan). The mango kernel also contains about 8-10% good quality fat which can be used for saponification. Its starch is used in confectionery industry like soap.

Symptoms

The disease is characterized by necrosis of tissues at the distal end of the fruit. The first symptoms is developed of a small etiolated area at the distal end which gradually spreads, turns nearly black and covers the tip completely. The tip is flattened with the outer skin turning hard and sunken. The inner portion of fruits is soft and yields a dark brown liquid due to rotting induced by saprophytic bacteria.

The disease commonly occurs when the fruits are about 6-10 weeks old or when they are reaching ripening stage. Apart from these factors, irrigation, condition of the tree and management practices also play important role in deciding the severity of the disorder.

Physiological factor

Gases like carbon monoxide, sulphur dioxide and ethylene constituting the fumes from brick kiln are known to damage growing tip of fruits and give rise to the symptoms of black tip.

Etiology

It has been confirmed by the majority of workers that bricks kilns fumes emitted from the burning of coal are harmful to the mango fruit and are solely responsible for causing black tip of mango.

The gases in coal fumes, sulphur dioxide, ethylene and carbon monoxide are especially toxic to the plants and of these sulphur dioxide causes the maximum damage. Wind direction and velocity play important role in increasing incidence of this disease.

Management

o The incidence of black tip can be minimized by the spray of borax (1 per cent) or other alkaline solutions like caustic (0.8 per cent) or washing (0.5 per cent) soda.
o The first spray of borax should be done positively at pea stage followed by two more sprays at 15 days interval.
o Trees sprayed three times with a solution of borax 0.6 per cent (600g of borax mixed in 100 litres of water) plus a sticker @ 10 litres per tree was almost free from black tip.
o Orchards should be at least at a distance of 1.6 kms in the east and west and 0.8 kms in the north and south from brick kiln.
o The chimney height of the kiln should be at least 15-18 meters.
o Although black tip of mango can be prevented by applying borax, the disease is not caused by the fruit surface that prevents direct entry of poisonous fumes or changed into a form which is less toxic.
o Restriction of new kiln sites to a safe distance stopping the working of kilns before the time of fruit-set and use of telescopic chimneys (12-15 m high).
o Mango decline is becoming a serious problem in many parts of northern India.
o On the old leaves, leaf tissues collapse in clearly defined marginal areas of brick red color towards the tip.
o Younger leaves generally do not show symptoms up to two months of their emergence.


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