Biscogniauxia nummularia - Beech Tar Crust or Charcoal Canker

 

I think this is most likely to be Biscogniauxia. Stated to be a significant parasite of Fagus sylvatica if the environmental conditions stress the tree in various ways - increasing risk drought is perceived as a bit of a worry for European Beech in Southeast England.

This is a section of dead hardwood in the trunk of one of these trees to the east of the main track from the car park at Dene Park. The fruiting body "erupts" through the bark nicely.

Are there any clues to why this bark appears dead in this image here? There is good evidence that these species occur in healthy living trees as endophytes and then become invasive under water stress conditions. Could the initial carving have possibly caused this overall wound that allowed a strip canker to get to work, and we are now seeing the results as the fruiting bodies appearing, perhaps later through the letters themselves?

Here, these fruiting bodies are just appearing recently on the heartwood of this large branch on the ground that tore away from the trunk maybe a couple of years ago. 

The species used to be known as Hypoxylon nummularium: this should now always be known as Biscogniauxia nummularia (Bull.) Kuntze. This genus is distinguished from Hypoxylon principally in lacking coloured stromatal pigments and in having an initial covering layer, lost at maturity, which bears conidia. Many species have effused and flattened rather than pulvinate stromata.

Biscogniauxia atropunctata is a saprophyte and parasite affecting oaks east of the rocky mountains, It starts as a blue-white fruiting crust with tiny black pimples, eventually darkening to black patches on dead and dying wood.

Biscogniauxia mediterranea is well known as the causative agent of charcoal canker in cork oak and is a serious problem in Portugal.

Biscogniauxia rosacearum may possibly be one of the main fungi that feed on grape vines and almonds.

Biscogniauxia species that produce interesting secondary metabolites can also be found in deep sea sub-floor sediments!