Saturday 23rd January, 2010

Pests, diseases, disorders, competing growth and unfavourable conditions (a field trip): the diseases

By Ash

Last Thursday my arboriculture class set out from college on a field trip to see a smörgåsbord of pests, diseases, disorders, competing growth and unfavourable conditions afflicting a variety of trees in the vicinity of York and Malton. Some of them were new to me, most I were already aware of, but it was a highly interesting way to spend a day and we got to see some cracking trees. Here’s a quick run-through of the diseases that we saw:

Supermassive sycamore (this photo falls a long way short of doing it justice) with decayed Dryad’s saddles. The one on the floor has fallen off the tree.

Dryad’s saddle (Polyporus squamosus) – A bracket fungi. Described in Jordan’s Fungi ¹ as “Large, creamy-brown scaly cap with cream pore-bearing under-surface, annual; parasitic on broad-leaf trees, also on stumps, favouring beech, elm and sycamore.” We only saw old and decaying specimens, but the sycamores (Acer pseudoplatanus) they had grown on were jaw-droppingly colossal - easily the biggest I’ve seen! These ancient sycamores formed an avenue along a road near Birdsall House. I’ve got to go back and get some decent photos of them in the summer before they collapse or get felled for safety reasons.

These crazy patterns are galleries produced by elm bark beetles.

Dutch elm disease – The Big Baddie. The current epidemic is caused by the fungus Ophiostma novo-ulmi, spread by elm bark beetles of the genus Scolytus. It is the most catastrophically devastating tree disease ever recorded in British history. On the field trip we saw a dead elm (Ulmus) replete with bark beetle galleries in the wood beneath the bark.

Cankers on a sycamore.

Canker – There are various kinds of cankers and a variety of causes of cankers. Strouts and Winter ² define a canker as a “clearly defined patch of dead and sunken or malformed bark”. We saw cankers on sycamore and red horse chestnut (Aesculus x carnea) - a hybrid amusingly described in the Collins Tree Guide ³ as a tree of “rather endearing ugliness”.

Huge ivy-covered canker on a red horse chestnut.

Razor strop on silver birch.

Birch polypore or razor strop (Piptoporus betulinus) – Another bracket-producing fungus, it is restricted to birch (Betula). We saw loads of razor strops on dead and drying silver birches (Betula pendula) in a small piece of woodland that has become waterlogged as a consequence of mining subsidence.

Ganoderma on a veteran English oak.

Ganoderma - A genus of bracket- (polypore) producing fungi that is parasitic on broad-leafed species. We saw a large, dead Ganoderma at the base of a huge and ancient English oak (Quercus robur), but we didn’t identify it to species level. The oak was extremely diseased and its days are sadly numbered.

Slime flux on the same oak.

Slime flux or bacterial wetwood – A bacterial infection causing the host to ooze infected sap from wounds or apparently healthy bark. According to Strouts and Winter ², bacterial wetwood is “common yet rarely results in overt disease”.

Inonotus hispidus on an ivy-clad ash.

Inonotus hispidus - Another polypore-producer that is parasitic on broad-leaves, particularly ash (Fraxinus excelsior). We saw several dead brackets on an ivy-covered ash growing by a stream.

Fomes fomentarius on silver birch.

Hoof fungus or tinder bracket (Fomes fomentarius) – Like you’d expect, the brackets of this fungus look like hooves. It favours birch – its modus operandi is similar to that of razor strop. We saw several of these brackets on the waterlogged birches.


¹ Jordan, M. (2004). The Encyclopedia of Fungi of Britain and Europe. Frances Lincoln.
² Strouts, R. G. and Winter, T. G. (2000). Diagnosis of ill-health in trees. The Stationary Office.
³ Johnson, O. and More, D. (2006). Collins Tree Guide. HarperCollins Publishers.

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tags: ash + birch + disease + elm + fungi + horse chestnut + info + ivy + oak + photos + sycamore

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6 comments for Pests, diseases, disorders, competing growth and unfavourable conditions (a field trip): the diseases

Kalle B.

23 Jan 2010 23:04:44

What about the fungus "Chalara fraxinea", causing ash dieback? I am not sure if it has reached the UK yet, if it hasn't you should have it there soon. It is coming from east, in the Baltic states, Scandinavia, Poland and Germany it is killing big parts of the ash populations. Where I live in southwestern Sweden about every singel ash tree is dead or dying. It is just as bad as the dutch elm disease, it is spreading extremely fast and kill trees in just a few years.

Ash

24 Jan 2010 14:04:34

Ash dieback is a new one to me. I've just had a brief read up on it on the internet and it sounds seriously nasty. A November 2009 Forestry Commission Biosecurity Programme Board information paper (available at tinyurl.com/bpbnov09 [pdf]) states that C. fraxinea hasn't reached Britain yet. I just can't imagine a countryside without ash. It must be terrible to see it in progress.

Katy

25 Jan 2010 03:57:31

Very cool! It's great to see fungi I'm familiar with look different in different situations and on different species. Thanks for posting these pics!

Reece

25 Jan 2010 16:46:43

I've heard a bit about ash dieback.
I've also witnessed elm trees die from Dutch Elm Disease. There's a few up the local woods that are dead. There's loads of surviving ones though, and I'll still be growing loads of elms next year.

Ash

25 Jan 2010 19:00:35

Thanks Katy. I've seen Ganoderma on oak, ash, alder (Alnus glutinosa) and cherry and I've seen razor strop on lots of birches, but the other brackets were new to me. I'll be keeping my eyes peeled!
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Reece - Are the surviving elms mature trees or saplings less than about twenty feet tall? I've read that the bark beetles tend only to attack trees (individuals or regrowth from roots) that have reached this height.

Reece

26 Jan 2010 17:17:00

The surviving elms are fairly big. Most are about as big as a two storey house. Some are smaller, some are saplings.
In other words, there are some medium sized ones and some small ones, but all the big ones have died off.
The ones I'm getting seed off from now on are medium sized, but there's a lot of saplings and suckers growing too.

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