Skip to Left navigation Skip to Main content Skip to Footer

University of Minnesota Extension

Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous Trees > Birch > Fungi growing on trunk or branches

Print Icon Email Icon Share Icon

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

1 of 4
  • Image: Armillaria root rot 1
  • Image: Armillaria root rot 2
  • Image: Armillaria root rot 3

Armillaria root rot
Armillaria spp.

  • 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
2 of 4
  • Image: Heart rot 1
  • Image: Heart rot 2
  • Image: Heart rot 3

Heart rot
Polyporus squamosus, Laetiporus sulphureus, Fomes
fomentarius, Phellinus igniarius, Piptoporus betulinus

  • 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
3 of 4
  • Image: Canker rot 1
  • Image: Canker rot 2
  • Image: Canker rot 3

Canker rot
(aka. sterile conk or cinder conk)
Inonotus obliquus

  • 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
  • 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
4 of 4
  • Image: Ganoderma root and butt rot 1
  • Image: Ganoderma root and butt rot 2

Ganoderma root and butt rot
(artist's conk)
Ganoderma applanatum

  • 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

Don't see what you're looking for?