Nectria cinnabarina is very common and initially grows saprophytically (feeding on already dead organic material) on dead or dying wood, including dead stubs left after incorrect pruning, wounds or growth damaged by frost or other conditions. It then moves into living wood, causing further dieback.
After causing dieback, the fungus forms its pustules, which produce spores that spread the disease further. These need damp conditions and are mainly dispersed by wind-blown rain and rain splash.