Leaves appear to have yellow or brownish trails and blotches. Leaves could also be distorted and have green blisters or pinpricks marks on lower surface. Leaf Miners spend the winter as pupa or larvae inside leaves attached to the trees or in leaves that have fallen. Tiny black flies, (adults) show during the spring when the new growth on the tree is about ½ inch to 1 inch long. Female flies make slits in the lower surface of the leaves to deposit the eggs. These flies survive by stabbing through the leaf surfaces to feed on the sap. The puncture marks that are seen on the leaves are caused by the feeding. Maggots hatch out of the eggs that were deposited into the leaves and they feed on the inner tissue. That causes the mines or trails that can be seen. The plant may drop all of its leaves and will remain bare until the following spring.