Congealed blobs of sap on lower trunks of peach and plum trees are result of….

Borer invasion. Peach tree borers tunnel around within the bases of the trunks. The congealed sap is evidence of their tunneling and damage. 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.