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If fruiting bodies of fungi form on the tree trunk or at the base, then the tree is diseased. In order to recognize how bad such an infestation can be, it is helpful to be able to identify the individual tree fungi.

In a nutshell

  • Tree mushrooms can also be either poisonous or edible
  • when a tree is infested with fungus, it spreads very quickly
  • Fungal spores are spread over a wide area by the wind
  • after a fungal infestation, the soil around the tree is also infested, the soil should be removed over a large area and disposed of
  • Fungicides are pointless here, the fruiting body on the outside indicates an internal infestation

leaf and needle fungi

There are many species of tree fungi. In order to be able to determine these, it must be recognized at which point they are located. For example, there are tree fungi that settle on leaves and needles:

Pine Shed (Lophodermium seditiosum)

Source: I.Sáček, senior, Lophodermium 10823, edited from Plantopedia, CC0 1.0
  • massive shedding of the needles
  • first turn yellow to brown-red
  • Pines and conifers affected
  • Fungus overwinters in spore stores
  • are on discarded needles
  • from there spread in spring
  • from bottom to top
  • when there is moisture, bearings open
  • Spurs are shot out
  • Pick up and discard any discarded needles

Notice: Infested waste wood from a distant branch or felled tree can still be used as wood for the fireplace or a campfire or fire bowl.

Rust fungi (Pucciniales)

Source: Björn S… , Rust fungus on Picea abies (42967760870), Edited by Plantopedia, CC BY-SA 2.0
  • Small pustules on top of leaves
  • yellow or red
  • Underside of spur bearing
  • Leaves die off over time
  • already dropping of leaves before autumn
  • usually not fatal
  • however, can weaken tree
  • often new leaf formation already in summer
  • very common as apple rust and pear rust
  • often reduces the quality of the harvest

Molds (Aspergillus)

  • many different types of mold
  • can be confused with powdery mildew
  • white coating on leaves
  • often after very wet, long periods of rain
  • not harmful to plant
  • not to be compared with food mold
  • Perform removal for aesthetic reasons only
  • often found under the trees

Notice: Outdoor mold is not like mold on indoor plants. Here you always have to intervene so that it does not move to the walls of your home and spread here.

mildew species

  • often seen on fruit trees
  • apple powdery mildew
  • American gooseberry powdery mildew
  • affects leaves and all green parts
  • wipeable coating on the upper side of the leaves
  • first white then dirty brown or grey
  • Leaves dry up
  • only plant trees that have been bred for mildew resistance
  • fight with fresh untreated cow's milk
  • available in health food stores or from farmers

Wood-destroying tree fungi

The wood-destroying fungi, which are usually found on the trunk or thick branches of a tree, are usually very dangerous for the tree and usually cannot be controlled sufficiently. Here they feed on the wood:

Bleeding layer fungus (Stereum sanguinolentum)

Source: Andreas Kunze, 2006-03-10 Stereum sanguinolentum, Edited by Plantopedia, CC BY-SA 3.0
  • large extension on the trunk
  • mainly on conifers
  • often on dead wood
  • Cones stick out horizontally from the trunk
  • if injured, mushroom immediately turns blood red
  • unobtrusive smell and taste
  • does not belong to the edible mushrooms
  • wood parasite

brown rot (destructive rot)

Source: Øyvind Holmstad, Råte i medfaret mellom to tømmerstokker, Edited by Plantopedia, CC0 1.0
  • actually known in tomato plants
  • is caused by various wood-decomposing fungi
  • penetrate wood and break down the cellulose
  • Cell walls dry out
  • the wood becomes brittle
  • Rub infested wood between fingers
  • only powder left
  • often with robinia, pine, oak and birch

Tip: A dead but still stable tree after a fungal attack does not necessarily have to be removed. Depending on the location in the garden, it is also very suitable as a climbing aid for climbing plants.

Burnt crust fungus (Kretzschmaria deusta)

Source: Björn S… , Kretzschmaria deusta (33744921074), Edited by Plantopedia, CC BY-SA 2.0
  • very feared
  • black, carbonaceous fruit bodies
  • sit on the bark
  • Fungal rot easily overlooked in its early stages
  • Main fruit with cushion-like aggregate fruiting bodies
  • Infestation occurs through injuries in the trunk
  • causes white rot that extends deep into the trunk
  • Causes strong traffic safety
  • especially lime, horse chestnut and beech are affected
  • determination is only possible through the microscope

Notice: If a fruit tree has to be cut down because of a fungus infestation, this does not require a permit. For all other trees, you should obtain a felling permit from the responsible authority, which will be granted in such a case without any problems.

Common mosaic layer fungus (Xylobolus frustulatus)

Source: Vik Nanda, Xylobolus frustulatus (363448878), Edited by Plantopedia, CC BY 2.0
  • many different earth colors
  • extensive
  • like a jigsaw puzzle
  • hence the name mosaic layer fungus
  • corky tough meat
  • Attention inedible
  • causes harmful white hole rot
  • Tree inevitably dies
  • also found on dead wood
  • destroys substance Wood is unsuitable for further processing

Pine Fire Sponge (Phellinus pini)

Source: caspar s, Phellinus pini (6080239505), Edited by Plantopedia, CC BY 2.0
  • from the fire sponge family
  • many species known
  • also on fruit trees mainly apple
  • dark brown fruit body
  • green color due to algae
  • Attention inedible
  • very tough meat
  • pleasant smell
  • affects all conifers, mainly pines

Varnish Porling (Ganoderma)

Glossy Lacquer Porling (Ganoderma lucidum), Source: GLJIVARSKO DRUSTVO NIS from Serbia, GANODERMA LUCIDUM (Curt. Fr.) Karsten (6006072051), Edited by Plantopedia, CC BY 2.0
  • different types
  • Shiny lacquer polypore also known as a medicinal mushroom
  • very harmful to trees
  • spreads through injuries in the bark
  • mostly from bottom to top
  • spreading very slowly
  • may have been in the trunk for decades
  • without symptoms
  • in the final phase tree can fall down
  • grow flat horizontally in a semicircular shape from the trunk

Notice: The fruiting body hanging on the outside of the trunk is not the problem, but rather the mycelium growing inwards, the mycelium. Therefore, removing the fungi from the outside is not enough to save the tree.

white rot (corrosion rot)

Source: Moinats, Pourriture blanche abies alba, Edited by Plantopedia, CC BY-SA 4.0
  • also caused by a fungal infestation
  • various fungi can be the cause
  • for example the lacquer polypore
  • whitening of the wood
  • defibration
  • loss of stability
  • Fungi break down lignin, hemicellulose and cellulose in wood

Tip: If a fruit tree has been attacked by a fungus and there is no danger to its stability, then this tree can continue to bear fruit for years and does not have to be felled immediately.

Tinder fungus (Fomes fomentarius)

Source: W.carter, Tinder fungus on a dead pine in Gullmarsskogen 2, Edited by Plantopedia, CC0 1.0
  • forms tubular layers on the trunk
  • Color rusty to orange brown
  • hard top
  • plate-shaped or hemispherical
  • hard meat
  • Attention inedible
  • mainly on deciduous trees
  • is easily mistaken for other sponges or Lacquer Porling
  • Medicinal mushroom in Chinese medicine

Notice: The tinder fungus was used in earlier times for the production of clothing, such as hats. Today it is still used to some extent for dyeing clothing.

mushrooms on shoots

Often there is also a fungal attack on the young shoots of a tree. If this is the case, then the determination is particularly important, since the wood can still be saved as a whole by removing all affected shoots:

False White Stem Cups (Hymenoscyphus fraxineus)

Source: Björn S… , Ash Dieback - Hymenoscyphus fraxineus (36040583332), Edited by Plantopedia, CC BY-SA 2.0
  • mainly on ash shoots
  • rediscovered in 2008
  • the white stalk cup not dangerous
  • but the doppelganger named here does
  • causative agent of ash dieback
  • probably introduced via Poland
  • Attention inedible
  • to be identified as small white to yellow tree fungi
  • with an upward-curved hat
  • mostly perched on twigs and branches

Pine dieback (Sphaeropsis sapinea)

  • yellow to red-brown discoloration on needles
  • Shoots die
  • roundish, small black fruit bodies
  • barely recognizable
  • turn dirty yellow to orange when wet
  • frequent occurrence in wet spring and hot summer
  • Damage often confused with road salt damage
  • Pine trees die within a few months of infestation
  • Water enough to prevent fungal attack
  • Remove and discard affected shoots

root fungi

Finally, attention must also be drawn to the various soil fungi that increasingly attach themselves to the roots of trees, feed on them and can thus destroy a tree from below if the infestation is not recognized in time:

Honey fungus species (Armillaria)

Honey fungus (Armillaria mellea), Source: George Chernilevsky, Armillaria mellea 2014 G1, Edited from Plantopedia, CC0 1.0
  • 30 different types
  • often in autumn at the foot of the tree
  • mostly in small groups
  • thin mushrooms up to 20 centimeters high
  • large forest pest
  • the trees usually die off
  • very harmful honey fungus (Armillaria mellea)
  • as well as the dark honey fungus (Armillaria ostoyae)
  • both capable of decomposing wood
  • both coniferous and deciduous trees

Tip: You can identify honey fungus as dangerous if it grows out of the ground further away from the tree. Then the fungus attacked the underground roots.

Root sponges (Heterobasidion)

Common root rot (Heterobasidion annosum), Source: Jason Hollinger, Annosus Root Rot (981717061), Edited by Plantopedia, CC BY 2.0
  • Common root sponge (Heterobasidion annosum)
  • pine root scum
  • also known as red rot
  • Attention inedible
  • sour smell
  • irregularly shaped humped fruit body
  • white to yellow color
  • causes root rot
  • can cause millions in damage in forestry

Tip: If a tree had to be felled due to a fungal infestation, the stump can remain for many years for decorative reasons, for example with a flower pot. Because it also offers a natural habitat for many microorganisms.

frequently asked Questions

Why are fungi on the trunk of a tree often dangerous?

Most of the tree fungi that you can see on the trunks of trees feed on the nutrients they pull from the wood. For this purpose, the wood is digested by the fungi, from which they draw their energy. Living wood is also decomposed in the process, which can lead to the long-term death of the trees.

Are tree mushrooms poisonous?

This question cannot be answered simply with a yes or a no. As with all other types of mushrooms, there are both edible and inedible, useful and harmful, and tender and tough mushrooms. Therefore, the toxicity of each individual tree fungus found should be clarified beforehand.

Which species of tree fungi are palatable and edible?

Both the oyster mushroom, which is very well known, and the velvet foot root are edible, with the former having already found its way into vegetarian and vegan cuisine. Both types of mushrooms can even be eaten after a frost, as they simply continue to grow again on the following frost-free days.

Should tree fungi be removed immediately upon detection?

If you have identified a tree fungus and been able to determine which fungus it is, you should remove the fruiting bodies immediately. Otherwise the fungus would spread further. For example, if a branch has already been severely affected, it makes more sense to remove it completely. Since the fungi are usually already too deep in the tree, spraying with fungicides is usually no longer helpful.

What is the worst thing that can happen with a fungal infestation?

If the fungi have been on the tree itself or on the roots for a long time without being detected, then the entire trunk is usually already infested. So that the tree doesn't fall down by itself and cause more damage, it can be cut down, since it can no longer be saved anyway.

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