Plant :Alstonia Appearance:Blisters (gall) on both sides,cutting galls leaves white fluid. After some time holes apppears in the blisters.so it seems some insect laid eggs. What kind of disease is this? It seems to be some kind of blisters on the leaves of a decorative plant. I'm guessing some insect laid eggs in it for eggs nourishment.
Would you please identify them and tell me how to treat them?