Question
We have a beautiful Pin Oak tree in our back yard and never had any trouble with it until now. On one side of our tree it's raining sap. Could this be caused from the large roots of the tree being cut when we put our new cement patio in last fall? It's only in one area of the tree/ what can we do to stop the sap from sprinkling out of it's leaves?

Answer
Sounds like an insect called aphids. Aphids suck the plant juices fro the leaves and excrete a substance called honeydew (which is sticky due to the high content of sugar). Control the aphids and you will control the sap. Spray the foliage with an insecticide for aphids (check with your local nursery/garden type store for a systemic insecticide for aphids on trees. Since all the foliage will have to be sprayed this can be a large job and may take a professional pest control person. There is a product that can be spread on the ground and watered in and the roots take it to the leaves killing the aphids.