I live in Beaverton, Oregon. All of the oak leaves seem to be turning brown and falling early this year. The backs of all the leaves falling have little black spots all over them and I see thousands of small bug flying around everyday.
My questions is what are the bugs and are they related to all the black spots on the leaves, or do I have two different problems? Also, what can I do to reduce the population of these bugs and what impact will they have on all the plants in my yard?
Thanks for your question. These appear to be oak lace bugs, Corythucha arcuata, and the spots on the leaves are actually their eggs.
While a high abundance of oak lace bugs might seem like a cause for concern, they tend to not cause much damage to mature, healthy plants. Oak lace bugs have many natural predators that help control and reduce booms in insect populations, which is likely what you are experiencing now.
There are a few ways to control oak lace bugs if you wish to do so. You can use high-pressure water to knock the insects off plants, there are also several different insecticide treatments you can use (but keep in mind that these can impact beneficial insects as well).
Here are some additional resources with tips for identification and treatment: