There are lots of possibilities, Fred. Those may be lady bugs you see, and their larvae. Both adults and larvae are voracious perdators of aphids. If there a lot of aphids there, I'd expect the lady bugs, too.
The blackened leaves could be several things, also. Birch leaf miner is a tiny insect that lays eggs inside the leaf. The larvae tunnel aound inside, eating the middle and leaving the top and bottom layers intact. If you hold the leaves up to light, you can seen the small larvae inside. Another possibility is the aphids causing enough damage to kill patches of the leaves. Let the lady bugs do their work.
Finally, there is a possibility of anthracnose (an-thrak-nos) disease. This is a fungus that is usually quite minor, but can be a problem if spring weather conditions are just right. The fungus kills angular patches of the leaves. It doesn’t usually harm the tree much, but severe defoliation could be a problem.
The best course of action is to locate a local certified arborist to inspect the tree and advise on the problems and solutions. You can find ISA Certified Arborists at International Society of Arboriculture.
Russ Carlson, RCA, BCMA
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