What is causing the leaves on my ash tree to clump and turn dark?
Within the last week or so our ash tree has started have a clumping of leaves (see pictures). Some of the bunches are starting to turn a dark, almost black color. Our neighbor's tree is also doing the same thing. Is there something wrong with our tree? If so, what can we do?
It looks like you have aphids. There are some aphids that can cause the leaves to curl up. To check for the aphids, I would uncurl the leaves and if there are lots of small white or green insects in there you know you have found the problem.
Here is a great fact sheet about aphids and shade trees:
Please let me know if you have any more questions or concerns.