Autumn leaf and coral spot fungus

The pink spots are the coral spot fungus Nectria cinnabarina. Coral Spot is a weak pathogen of broadleaf trees, which goes through a spongy conidial stage (producing asexual spores) and a tough perithecial stage (producing sexual spores).

The effect of Coral Spot infection is that usually small twigs and branches die back, and then dense clusters of soft, pinhead-sized pink fungal blobs (the sexual stage in the complex lifecycle of this fungus) break through the thin bark. Later the blobs harden and turn dark reddish-brown (this is the conidial stage in the lifecycle), and by this time the infected timber is so weak that it tends to snap off during windy weather.

Nectria, the genus name, comes from the same stem as necrosis and means 'killer'. The specific epithet cinnabarina means cinnabar coloured, like red lead.

Despite being a nasty little pathogen Coral Spot is very pretty to the human eye. It is said to be poisonous but I doubt that anyone would be tempted to chew it.