July 2010. Leaves from mango, India.
There was general agreement that the leaf lesions were those of anthracnose, Colletotrichum gloeosporioides or C acutatum. There is evidence of the circular development pattern of the lesions on the leaves, but isolation from the developing lesions is needed to be sure.
Sanitation and fungicide sprays can help control this disease. A useful summary of IPM measures against anthracnose in the Philippines is to be found in the pestnet message 8261 – see below. The methodology involved sanitation, chemical control. bagging the fruit and pruning. Sanitation involved removing dead branches and decayed leaves throughout the year, fungicdes from the 10th day of flower induction until 20 days from harvest, and fruit bagging is 50-60 days after flower induction.
The second photo (four leaves, right) looks like a collection of various things, apparently non-parasitic conditions, either nutrient deficiencies or toxicities. Boron toxicity was suggested. Boron is taken up very quickly by mango when applied to the soil. The trees need little amounts often, not a large amount at one time. Knowing what has been applied to the trees, and a soil analysis might yield helpful clues.