Black tip of mango is caused by

The black tip of mango is caused by pollutant gases such as carbon monoxide, Sulphur dioxide, flouride, etc that emanate from brick kiln fumes. It is not caused by any microorganisms such as viruses, fungi and bacteria.
The black tip is a serious disorder that is capable of causing considerable set back to the grower. Among the commercial cultivars, Dashehari is most prone to the disorder, while Lucknow Safeda is least.
A spray of 1% borax at the time of fruit set, followed by two more sprays at 10-day intervals might be useful in controlling the disorder.