Zimmerman pine moth is the insect that causes the pitch/sap to occur on the upper side of the branch crotch. When feeding damage is severe at all the crotches at a particular whorl of branches, the trunk may break off at that whorl.
Prune out damaged wood. Check with your local land grant university (Cooperative) Extension Service for the recommended insecticide. Control may be done in spring when saucer magnolia is in pink bud to early bloom or in mid to late summer when panicle hydrangea is pink.
Written by James Schuster, Extension Educator, Horticulture, and reviewed by Dr.Philip L. Nixon, Extension Specialist-Entomology, Department of Natural Resources and Environmental Sciences University of Illinois at Urbana-Champaign.