What's wrong with my plant? : Garden : University of Minnesota Extension

Birch > Trunk/Branches > Fungi growing on trunk or branches

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Clusters of honey-colored mushrooms may grow at the base of the tree in fall
Wood is decayed, white, soft and spongy, and this may extend from the base of the tree well up into the trunk
Thick black, shoestring-like fungus can sometimes be seen under the bark, around roots and in the soil around the base of the tree
Infected trees have poor growth, dead branches in the upper canopy, undersized and/or yellow leaves
Flat white sheets of fungal growth (mycelia fans) grow between the bark and sapwood at the base of infected trees
More information on Armillaria root rot

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Many colors, shapes and sizes of fruiting bodies may be seen
Fungal fruiting bodies arise along the stem; often near a pruning wound, crack or other wound
In cross section of the trunk, the wood at the center is discolored, soft, crumbling, stringy or spongy
Canopy may show no symptoms, or may have small yellowing leaves or dead branches depending on the extent of the decay
More information on heart rot

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Rough, cracked black, knob or cone like fungal growths protrudes from trunk, often near an old wound or branch stub
Internally fungal growth is spongy, colored yellow-brown to
rust-brown
Infected trees often break at the point of the fungal growth
Mottled white and reddish brown wood decay can be seen within infected trunks
More information on Canker rot

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Fungal conks, a semicircle shelf fungi, can be found from the base of the tree up to 3 feet high on the trunk
Conks are reddish-brown and shiny on top, white and porous underneath; a rim of white may be visible on the edge of
growing conks
Infected wood at the base of the tree is white, soft, stringy
or spongy
Infected trees frequently break or fall over in storms
Leaves are smaller in size and turn yellow earlier than normal
Canopy appears thin with few leaves and multiple dead branches
More information on Ganoderma butt rot