Hi, I live in California where we have been in a drought for 3+ years. My oak trees are not doing so well. We had to have one cut down when it died. The tree cutter said it may have had a borer bettle. We have now been watering the oaks plus we are thinking about getting a spray. I heard Astro-insecticide was a good one to keep the pests away. Any idea? Also I noticed that I have another oak that is leaking sap close to the bottom of the tree. The tree has several small cracks where it is leaking as well.