Linden Leaf Blotch
I am receiving pictures and samples of basswood and linden leaves. This is a common occurrence at this time of year, and there are several possible reasons for the discoloration and premature falling of these leaves. However, one of the most common is a disease called linden leaf blotch. The blotches begin in late summer, often as small specks that expand to larger blotches. A characteristic of the dark brown blotches is the feathery margins. The disease can result in complete defoliation of the tree by mid-September.
There really is no control other than remove and destroy the fallen leaves, often impractical, and if the spring is relatively dry the disease is often minor and only results in some leaf discoloration.
Frogeye Leaf Spot
Frogeye leaf spot is showing up on apple trees (and crabapples) in the southern part of the state. The most common symptoms for this disease are concentric patterns of light brown to tan irregular circles appearing on the upper leaf surface. There will be tiny black dots in the center of these circles and these are the fruiting structures.
The disease alone is not a threat to the tree; just discoloration of the leaves, but this is often associated with black rot, a serious canker disease that can result in branch dieback. Apple trees with leaves exhibiting these symptoms should be examined for small dark cankers on branches and if found, these infected branches should be removed.
