Gummosis is the symptom of several diseases and insect damage. Sticky sap oozes from trunks and branches.
Identify the problem
Identify the cause of the gummosis and treat as appropriate; look for insect damage and holes and check the roots are not suffering from root rot. If the roots are sound and not in continually wet soil and there is no evidence of boring insects it is likely that the plant is suffering from bacterial blast canker.
Carry out a winter spray programme to protect your plants.