At Jyothy Institute of Technology (Bangalore) farm, infected leaves were found as shown below
On both sides of leaf surface numerous small, superficial and blackish distinct tar like spots which surrounded by yellow zone were observed. Along with the tar spots, there was light yellowish stroma and mats of hyphae of fungus were found on the upper surface of leaves. They were observed under foldscope and spores were found.
It was tar leaf spots. This caused by Rhytisma acerinum fungus.