Dear Mr. Velavan,
Do you see a large nest of black ants on the top of the tree? I have
seen trees that have such nests have black stem. The leaves in your
picture looks totally black. Trees with the nest of these ants have
leaves that turn black but not as black as the leaves in your pictures
are. The ants harbour mealybugs which are sucking pests. They secrete
honey dew which the ants feed on. The ants and these sucking pests
have a symbiotic relationship. The mealybugs are immobile and depend
upon the ants to move their young ones to succulent areas where they
live for the length of their lives.
I must mention, I have not seen leaves so completely black.