pine pitch canker
A fungal pathogen primarily of several pine species, thought to have originated in Mexico, now present in North America, Asia, South Africa and southern Europe. The spores infect the host through stem wounds created by insects, pruning, strong winds etc. Small branches in the outer crown, typically infected first, are girdled, killed and give rise to resinous cankers. The disease then progresses by independent infections to larger branches, and weakened trees may then be attacked by bark beetles and eventually killed. The disease, present on seed, in soil or in the litter layer, can also kill seedlings. In Britain it is a potential alien invasive species.