Question: What causes congealed blobs of sap on the lower trunks of my peach and plum trees?
Answer: Those are the result of borer invasion. The peach tree borers tunnel around within the bases of the trunks. The congealed sap is evidence of their tunneling and damage. They probably result in the death of 90 percent of the peach and plum trees that die in Texas each year. It is much easier to prevent them than to control existing populations. Apply a borer-preventive insecticide spray the last week of August each year beginning with the year the tree is planted.