#FungiFriday: the most feared fungus in the world

Fungi Friday 26th June 2020

For some reason I decided to write a weekly Fungi Friday blog in 2020. It might have been the worst possible year to attempt this. It’s true that fungi peaks in the autumn but some of the more gentle, milder and wetter months of the year can give fungi an earlier chance. Not so in 2020, as this blog has complained for the past few weeks, it’s been very dry in southern England.

A recent storm didn’t reach Sussex but did pass through London and seems to have given fungi there a boost.

I could blame a global pandemic for the difficulty in finding fungi this spring and summer, but the dryness has been the main problem.

There are only so many dry (literally) blogs you can write about the lack of the thing you want to write about. This week I thought it would be a chance to cover a species that is one of the best known in the world and actually forms the largest organism on Earth. It’s also ‘feared/hated by gardeners’. I seem to use that phrase a lot in this line of unpaid work. What’s the species? It’s honey fungus.

Every time I take a photo of these ‘boot laces’, I always intend to file it somewhere easy to find. That never happens so above is a low-res phone pic of a honey fungus mycelium (the fungal network of hyphae, a root-like structure that forms the living, physical structure of the organism). This can often be found underneath the bark of a tree that has fallen down or that has died due to the impact of honey fungus. These ‘boot laces’ are also what represent the largest life form on Earth. That’s a humongous fungus, some 2384 acres in size.

That species is Armillaria oystayae but it’s not the case of a mushroom or toadstool over 2000 acres in size – can you imagine how much that would stink when it began to decay? Because that is only the apple on the tree, whereas the mycelium is the living and breathing fungus itself. The fungi above had moved in on a tree that had been harmed by development, with likely damage to the roots, making the tree vulnerable. No one described the developers as pests in that instance. One suggestion was for the tree to be felled just because the fungus was present. That’s a terrible idea.

Honey fungus is renowned for its parasitic potential. Armillaria oystayae is a ‘pest’ for foresters. I would argue that honey fungus, and other species like it, is simply living in a nature-depleted world where ‘naturally-occuring’ species diversity has been destroyed by industrial monocultures in farming and forestry, and development that does not take account of the landscape it is replacing. They are also just trying to survive and taking advantage of niches which are presented to them.

If fungi have been on Earth for 1billion years, they have evolved in a much more species-rich biosphere, rather than one we dominate now, which, in the case of Western Europe, is suffering from a loss of ancient semi-natural woodland and the associated habitat mosaics and species. In this case I mean there are fewer trees and less dead and decaying wood, the latter of which is a vital ingredient in a functioning and biodiverse ecosystem. Honey fungus, just like us humans, needs food and somewhere to live. It just so happens that honey fungi eat where they live and what they live on. Sometimes they also kill it. Sound familiar? Just ask Planet Earth.

The most common species of honey fungus that occurs in Britain is Armillaria mellea. In actual fact it’s an indicator of ancient woodland, which means that people can’t use xenophobic language around ‘alien invasion’ to explain why it could be a problem. An ancient woodland indicator is used to show us that it is over 400 years old in Britain and Europe. In my view, this is just another species which highlights our own ignorance – we think we can control nature and that anything which doesn’t stick to the script must be destroyed or is a pest. Covid-19 is teaching us in a tragic fashion that we were wrong about that.

It’s true that honey fungus has parasitic tendencies and therefore can kill trees through a process of starving it of nutrients, rather than the supportive biological process of providing the tree with things it can’t get (a mycorrhizal relationship). But as a tree inspection professional once said, trees are not a safety issue until we show up.

One thing that appears to work in honey fungus’s favour is its edibility. However, from what I know it’s only something that can be eaten in moderation and it does cause stomach upsets in some people. It’s definitely not a way of ‘getting rid of it’ from your garden, because the mycelium is there as well. And no one defeated an apple tree by eating all its fruit.

What can you do if you find it at the bottom of a tree? The only advice I have is not to panic and do something that causes more damage. The next step is to learn to love fungi and appreciate that trees die too, and fungi is there to help create space for more life. Beyond the loss of a much-loved tree, the main problem is our own rigid views of how the landscape lives and dies.

Thanks for reading.

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