The Curse of the Black Spot

 

The curse of the black spot! Tar spot fungus Rhytisma acerinum, that disfigures sycamore leaves in summer, continues to develop on its dead, decaying foliage in the leaf litter. The black spots become increasingly wrinkly as winter progress, then hundreds of asci - microscopically small flasks filled with needle-shaped spores - develop along the ridges. When spring arrives the spores are released into the air, just in time for them to infect a new crop of sycamore leaves, where they germinate and invade through the breathing pores (stomata) in the leaf surface.

Tar spot fungus is less common on urban sycamores that on trees in rural areas and it used to be thought that this was because the fungus was susceptible to sulphur dioxide in polluted city air. A more likely explanation could be that the fungus is less common on city sycamores because their fallen autumn leaves tend to be removed by councils from public places, so the annual cycle of reinfection from dead infected leaves is broken.

Fog and Fungi

A while back I posted about threats to the future of the Bishop of Durham's deer park at Auckland Park, in Bishop Auckland in County Durham. Thankfully these seem to have abated, much to the relief of all those who love the place. It's one of our favourite Sunday morning walks - even in the fog.

The park is at its best in autumn ....

.... especially when fog adds a touch of liquid magic to the spiders' webs.

I think it was Oliver Rackham, the noted tree and woodland expert, who once remarked that the only thing more useful to wildlife than a live tree was a dead tree. He was referring to the vast range of organisms - invertebrates, fungi, etc. - that live in or on the dead wood during a tree's protracted afterlife. Whoever manages the park at Bishop Auckland leaves plenty of dead wood for the benefit of organisms that thrive on it - like these tiers of bracket fungi (Ganoderma sp. I think) in the hollow trunk of this dead beech.

Some of the living beeches are under attack by honey fungus and their days are numbered - but there are also plenty of healthy trees and some replanting.

The stumps of old sweet chestnuts host these developing puffballs.

Sycamore, with the black spots of Rhytisma acerinum on the leaf blade.

Some of the living trees have magnificent rings of toadstools around their bases - I guess that these are a mycorrhizal species, that exist in a mutually beneficial association with the trees.

Not sure what these are, on a decaying beech stump. During the prolonged afterlife of the dead trees a whole succession of toadstools appear, some for just a few days.