There are borers that are getting under the bark of the pine and eat away the living layer under the surface so you won’t see them. You might notice tiny holes where they went in or sap leaking from the trunk from those holes. The only treatment is with a systemic insecticide like Bonide Annual Tree and Shrub Insect Killer. You dilute it and pour ir at the base of the tree. The tree takes up the insecticide and it flows up into all the parts of the tree and kills whatever is eating it. The amount needed depends on the size of the tree so be sure to read and follow the directions on the package.