River Birch -- powdery mildew?
Many of the leaves on my River Birch have a white powder on them. I am guessing it is powdery mildew. Is there any preventative measures that I can take to keep the tree healthy? How can I get rid of the mildew? The tree is located near my rain garden with full afternoon sun. I have included pictures.
Howard County Maryland
This is the work of the Spiny witch hazel gall aphid (Hamamelistes spinosus).
It is a common but not serious spring pest on river birch trees, and then moves to witch hazel to complete it's life cycle.
You can learn more about it on this page from our website: