It is mealybug infestation. Both nymphs and adult female insect suck the sap from tender leaves, shoots, inflorescence and fruits. The severe infestation leads to wilting and affects fruit setting.

Mealybugs secretes honeydew (a sugary substance) which causes sooty mold. The infected leaves and inflorescence become shiny black and sticky because several species of fungus which grows on this honeydew.
Mealybugs are always associated with ants (ants feeds on honeydew and in return helps mealybug in spreading to different parts of plant).

Management:
1. Collect and burn fallen leaves, twigs and fruits.
2. Mealybugs lay eggs in soil near tree trunk. Dig deep around the tree to expose eggs and nymphs to sunlight.
3. After hatching the nymphs start climbing tree and suck sap. To avoid this band the tree trunks with polythene sheet (400 gauge, 30 cm wide) at a height of about 30 cm from the ground level and apply grease at the lower edge of band.
4. To control insects already on tree you can spray fish oil rosin soap or neem oil or basic soap spray (add 2 tablespoons of liquid dish detergent or baby shampoo to 1 gallon of water).
5. Also soil application of the spores of the fungus, Beauveria bassiana helps in reducing mealybug population.