It sounds like there are already some insects present if you see woodpeckers.* They will help to clean up the pests.* The bleeding of sap you see is from the woodpecker activity.* I would suggest you do supportive care of your tree and watch it carefully for any decline.* If there has been a change in the area such as extensive landscaping, heavy equipment near the tree, excess mulch applied or flooding, etc you will need to take corrective measures.* Take a look here too.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.