What causes brown spots on Aspen and Apple Tree Leaves?
Aspen trees and some of the apple tree varieties have brown/black spots on their leaves. This is various leaf spot fungus. Trees with leaf fungus problems are best treated when the leaves are not on the trees. In the fall after leaf drop, thoroughly rake up and throw away the leaves. Overwintering leaves are a source of infection the following spring. If your trees have leaf fungus problems every year, spraying with a fungicide in the spring as the leaves are emerging from the buds and one or two more times during the summer, will reduce the leaf fungus problems.
