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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous Trees > Oak > Leaves undersized and yellow

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Oak > Leaves > Leaves undersized and yellow

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  • Image: Iron chlorosis 1
  • Image: Iron chlorosis 2
  • Image: Iron chlorosis 3

Iron chlorosis

  • Affected trees have poor growth, undersized leaves
  • Leaf blades that are supposed to be green are yellow but leaf veins remain green
  • Most severe on branch tips or new growth
  • Common on pin oaks (Quercus palustris)
  • More information on Iron chlorosis...
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  • Image: Ganoderma butt rot 1
  • Image: Ganoderma butt rot 2
  • Image: Ganoderma butt rot 3

Ganoderma butt rot
Ganoderma applanatum

  • Leaves are smaller in size and turn yellow earlier than normal
  • Canopy appears thin with few leaves and multiple dead branches
  • 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
  • More information on Ganoderma butt rot...
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  • Image: Armillaria root rot 1
  • Image: Armillaria root rot 2
  • Image: Armillaria root rot 3

Armillaria root rot
Armillaria gallica and Armillaria spp.

  • Infected trees have poor growth, dead branches in the upper canopy, undersized and/or yellow leaves
  • Flat white sheets of fungal mycelia (mycelia fans) grow between the bark and sapwood at the base of infected trees
  • Thick black, shoestring-like fungus can sometimes be seen under the bark, around roots and in the soil around the base of the tree
  • Wood is decayed, white, soft and spongy, and this may extend from the base of the tree well up into the trunk
  • Trees frequently break or fall over in storms
  • Clusters of honey-colored mushrooms may grow at the base of the tree in fall
  • Twolined chestnut borers often found on trees affected by Armillaria root rot
  • More information on Armillaria root rot...
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  • Image: Heart rot 1
  • Image: Heart rot 2
  • Image: Heart rot 3

Heart rot
Laetiporus sulphureus, Phellinus everhartii, Phellinus
igniarius, and others

  • The canopy may show no symptoms or may have small yellowing leaves or dead branches depending on the extent of the trunk decay
  • In cross section of the trunk, the wood at the center is discolored, soft, crumbling, stringy or spongy
  • Fungal fruiting bodies arise along the stem, near a pruning wound, crack or other wound
  • Many shapes and sizes of fungal fruiting bodies may be seen
  • Phellinus spp. have hoof shaped fruiting bodies that are black on top and yellow brown underneath
  • Laetiporus sp. have folds of yellow to bright orange fungal tissue arising in a clump
  • More information on Heart rot...

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