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  • David Humphries

    Article: Arboreal Fungi

    59a918777aa19_ScreenShot2017-09-01at09_20_44.png.c4c54a975fa7bd11152c42d2f8c7decf.png59a9187a0dbe2_ScreenShot2017-09-01at09_20_58.png.6980fc91b2961b5356f9dd7fbda12293.pngThis article looks at some of the ‘usual (& unusual) suspects’ in tree-specific mycology.  This is based on UK experience but many will be familiar to US and ANZ readers and the generics will certainly be similar.


    Fungi can be found in trees pretty much throughout the year. Perennial brackets (like Fomes fomentarius right ) put on incremental spore layers each growing cycle and can persist for years. Whereas annual fruiting bodies (like Inonotus hispidus right) are relatively short lived and ‘fruit’ once a year producing one or many bodies which desiccate after sporulation. The developing Inonotus shot (right) shows last year’s fruit body scar as dark patches.



    A recent study (in the American Journal of Botany) suggested that there are an estimated 5 million species of fungi on the planet, with somewhere in the region of 1200 new species recorded each year. This makes knowing the majority of the tree associated ones a tall order!





    59a91aeca199d_ScreenShot2017-09-01at09_31_23.png.0f5dec2ebb7eec7cec199160605f66b1.pngThere are many identification books & online resources available, but these generally deal with the fungal kingdom as a whole and not specifically the ones associated with trees. However, in the last couple of years there have been a small number of Tree specific fungi resources that have become available such as the UK’s Arboricultural Association’s Fungi on Trees – an Arborists Field Guide & also The Arbtalk Tree Fungi Id App for smart phones.  Both of these are specifically designed with the Arborist in mind for use out in the field(and up in the trees. 




    Screen Shot 2017-09-01 at 09.32.31.pngThere are a number of ways to help in tracking down an identification, including;

    • the tree host
    • does the fruit body have a stem or not
    • are there pores or gills
    • the colour of the spore
    • the type of flesh & tube layer
    • documenting it and sharing with colleagues and online Arb & Ecology communities
    • sending in samples to mycology labs, all of which can help identify which fun- gal specimen you are dealing with.


    Depending on its particular development stage, some of the more useful features to look at when trying to identify fungi, are their method of dispersing spore. In essence this is how fungi produces and distributes its spores.





    The three main types of structures from which spore are dispersed are;

    • Gills
    • Teeth/Spines
    • Pores



    59a91c7611c30_ScreenShot2017-09-01at09_37_34.png.19c4b830d6ff4cb41c69349ce86731b8.pngA good example of gilled fungi would be Pleurotus ostreatus – The oyster and Flammulina velutipes – the velvet shank (shown above) with fully developed ‘bracket’ and also as developing ‘polyps’.
    An example of fungi with teeth/spines would be Hericium erinaceus – The bearded tooth and a good example of fungi with pores, would be Polyporus squamosus – the dryads saddle


    The colour & size of the spore (fungal seed) varies considerably, this is a characteristic that helps (microscopically) to confirm a species.

    The obvious ‘black’ spore of Daldinia concentrica – King Alfreds cakes are shown below

    The white spore of Perenniporia fraxinea & below right the cocoa powder coloured spore (on the leaves of ivy) of Ganoderma resinaceum.

    The colour of the flesh & tube layer of certain fruit bodies, is again a good indicator of one species over another.




     Below is a sliced wedge taken from the fruit bodies of Ganoderma resinaceum (annual fruiting body), Ganoderma applanatum (perennial fruiting body) and Fistulina hepatica (annual fruiting body).






    The speed with which large fruit bodies can develop can be remarkable.  Here, Laetiporus sulphureus (chicken of the woods) is tracked in time lapse from early on through to desiccation after it has sporulated. The above pictures were taken on an oak over a 37 day period within an old woodpecker hole.





    Knowing the type of strategist a particular fungal species might be, is important in helping build toward an informed judgement on managing the structural parts of a tree either within a long term management plan for the tree or operationally during rigged dismantles


    There are a number of types of decay associated with the different species of fungi.

    • White rot – degrades the lignin and generally equates to soft spongy collapse (Pic Below Left in Horse Chestnut).  Examples include - Ganoderma spp, Armillaria spp, Heterobasidion annosum
    • Simultaneous white rot - degrades cellulose & lignin.  Examples include – Fomes fomentarius, Inonotus hispidus
    • Selective delignification - degrades areas of lignin. Examples include – Ganoderma resinaceum , Ganoderma pfeiferri , Inonotus dryadeus
    • Soft rot – degrading cellulose, later may degrade lignin. Examples include – Kretzschmaria duesta
    • Brown rot – degrades cellulose to produce a brittle-type failure (Pic Below Centre in Oak). Examples include – Laetiporus sulphureus, Fistulina hepatica, Phaeolus schweinitzii, Rigidoporus ulmarius, Piptoporus spp


    Each fungal species will have its own strategy for entering a tree, the different types of strategy can be described as;



    This is where entry is via spore on exposed wood (eg, lightning strikes (A), collision (B) & old pruning wounds (C)). Examples include – Fistulina hepatica & Polyporus squamosus



    Fungal species that are latent (lay dormant) inside the host awaiting structural or biological weakness. (eg branch breakage via storm or root plate rock) include Piptoporus betulinus (birch polypore) and Heterobasidion annosum (root rot)



    Consumes the static mass that is no longer needed by the tree for growing Introduced to the tree via exposed heart- wood/sapwood (Rigidoporus ulmarius , Inonotus dryadeus (pic  Below Right))





    Attacks the trees vascular system, shut-ting down & killing its host from roots up. (Armillaria mellea) Normally acting as a secondary coloniser of weakened trees.



    A look at points of failure associated with specific decay fungi:
    Ganoderma sp can be found from the base of a tree to crown break.  Below Left is a veteran lapsed Beech pollard from Burnham Beeches in the UK with old pollard poles that have succumbed and torn out due to the white rot of Ganoderma applanatum.

    Next (Below Centre Left) is the basal trunk failure on oak from Ganoderma resinaceum which is predominantly selective delignification (where lignin is preferentially degraded) leading to a more brittle decay than white rot.



    Merripilus giganteus, (Below Center Right) creates a white sponge-like rot of the underside of lateral guy roots, can (but not always) lead to complete root plate failure.  Some trees have been known to co-exist with this species for many years.
    The next image (Below Far Right) shows an air-spaded root plate with Meripilius that is only affecting one side of the tree & its associated canopy. The other side is still served by non-affected roots and still functions (although having been subject to a reduction).






    Fomes fomentarius, photos (Below Left and Below Centre Left) here on beech in northern Spain & a mid trunk failure.  Simultaneus white rot, degrading both the lignin & cellulose, can lead to trunk collapse.


    Trunk and branch failure from the brown rot of Laetiporus sulphureus here on beech (Below Centre Right) and oak (Below Right).


    Both conifers and broadleaf trees host this species, where it breaks down the cellulose at an early stage.






    Trunk failure from Fistulina hepatica here on oak (pic Below Left & Below Centre Left) , similar to Laetiporus in that it is a brown rot decayer


    Trunk & branch failure – Inonotus hispidus (pic Bottom Centre Right) creating a simultaneous white rot as seen here within this ash branch (pic Bottom Right).


    Pic Right: Stem failure via white rot of Polyporus squamosus









    Sometimes there may be more than one fungi at play within a host, this adds complication to predicting how failure may occur.


    Below Left: Fomes fomentarius & Ganoderma resinaceum 


    Below: Piptoporus betulinus & Fomes fomentarius


    Below Right: Laetiporus sulphureus & Ganoderma applanatum





    59a9298de2aa9_ScreenShot2017-09-01at10_33_53.png.2062058f8c8241d1d83ef784a324ee27.pngThis can mean there may also be different types of decay localised within a tree.
    In this picture (Right) is the white rot of Fomes & the brown rot of Piptoporus within birch.



    Where there is suspected dysfunction of a branch/union associated with fungal decay, it is good practice to assess the branch & its union as thoroughly as possible from the ground before choosing it as primary anchor point for ascent

    Access to a monocular or a good pair of binoculars is useful.(pic Below Left)
    I hear/read (too often) of climbers from all over the world having had their TIP fail on them whilst on initial ascent, (due to unforeseen biomechanical or decay issues) leading to severe injuries or sadly even fatalities.


    A good example of where a particular fungal induced dysfunction is worth taking the extra time to assess for potential weakness is Massaria Disease of Plane (Splanchnonema platani). Pic Below Centre Left.  This (‘non’ fruitbody forming) fungi, creates lesions on the upper-sides of branches.  The unions of these branches are often weakly attached and prone to snap.  The decay is noted as being a soft rot which can lead to a brittle type fracture failure under load.  There can also be a secondary decay in association by the white rotting Auricularia sp.

    Often the visual symptoms of Massaria do not readily show from the ground so caution is advised. For further information on MDP, the London Tree Officers Association are putting together a guidance document, which will be available on their web site this autumn.


    Oudemansiella mucida (the porcelain fungi, Pic Below Centre Right) is another example of where a branch may be structurally compromised and not seen from the ground without thorough inspection.  It is a saprophytic fungi creating a simultaneous white rot on dead/dysfunctional parts of beech trees.  Unlike Massaria, this one does fruit, which helps with assessment & identification (although usually only seen fruiting between late summer to late autumn)


    As well as legislation to protect the myriad of different birds, bats & invertebrate species whilst working on and around mature & veteran trees, it’s also important to have a good working knowledge of the habitat aspect of various fungal species that are afforded protection in the UK.
    A significant number of UK BAP priority fungi species have been identified as being the most threatened under the JNCC’s (Joint Nature Conservation Committee) UK Biodiversity Action Plan. Red data book species such as Podoscypha mulizonata, Piptoporus quercinus(Below Right) & Hericium errinaceus each have biodiversity action plans assigned to highlight their vulnerability, with priority given to their conservation status. Trees that host these rare species should be assessed


    Link to the most recent UK BAP priority fungi species (including lichens)







    59a92d7ba0437_ScreenShot2017-09-01at10_50_37.png.c22f1022daf5b8c6b20504f43ea30f96.pngASSESSING DECAY & DYSFUNCTION ASSOCIATED WITH DECAY SPECIFIC FUNGI
    Using VTA (visual tree assessment), to see if a tree (or tree part) is adapting to decay/dysfunction, & looking specifically at reaction in the body language of trees. Using decay detection equipment such as micro drills, tomographs & thermal imaging cameras.


    The above tools are predominantly used on the ground but can be taken aloft into the canopy to assess upper trunks & main scaffold branches.



    An additional tool in our collective assessment arsenal is using the relatively simple technique of ‘sounding’ to assess the quality of woody volumes with a hammer.

    The pictures Below Left and Below Centre Left show a fibre scope looking into a horse chestnut cavity at a Saprophytic coprinus sp
    The pictures Below Right and Below Centre Right show a Meripilus affected beech having its roots cleared of soil and then sounded with a thor soft faced hammer.







    Finally, a general nod to having an awareness of the spreading of fungal spores (and other pests & disease for that matter) through our work as Arborists within the canopy of trees. Although there are an estimated 10,000 million spores released from a single fruit body, this shouldn’t make us blasé about the part we perhaps play in spreading fungi via the very tools & PPE we use day in and day out, often across new un-connected sites.

    It’s relatively easy to spot the multi coloured fungi dust as shown earlier in this piece (and bacterial spore) during sporulation. So don’t forget to be mind- ful of the use of appropriate disinfection of fabrics, ropes & and soles of boots. It does us no harm to remind ourselves once in a while, that it’s not only small critters that have the potential to be vectors!

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