Apple Leaf with the tunnels of Leaf Miners and round patches of fungal or bacterial attack.
Leaf miners start life when their eggs hatch in a young leaf. They grow as they eat, creating these sinuous broadening river-like patterns in the leaf.
The tree responds to infection by sealing off the infected areas, creating dark patches. Finally, the tree abandons the leaf, withdrawing chlorophyll and nutrients (except from the sealed-off areas), leaving it yellow and ready to fall - before autumn comes.