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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous Trees > Elm > Leaves in the entire canopy yellow

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Elm > Leaves > Leaves in the entire canopy yellow

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  • Image: Dutch elm disease 1
  • Image: Dutch elm disease 2
  • Image: Dutch elm disease 3

Dutch elm disease
Ophiostoma ulmi and Ophiostoma novo-ulmi

  • Leaves turn yellow, wilt or shrivel, turn brown, then fall off the branch
  • Initial infection occurs on one branch; disease may quickly progress to all branches
  • Peel back bark on symptomatic branch to reveal brown streaking on wood
  • Healthy elms neighboring infected elms soon show symptoms due to spread through root grafts
  • Wood pecker holes with bark loss is common on trees killed by Dutch Elm Disease
  • American, red or slippery and rock elm are highly susceptible
  • More information on Dutch elm disease...
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  • Image: Elm yellows or Elm phloem necrosis 1
  • Image: Elm yellows or Elm phloem necrosis 2
  • Image: Elm yellows or Elm phloem necrosis 3

Elm yellows or Elm phloem necrosis
Elm yellows group or clover proliferation group

  • Leaves in the entire canopy turn yellow, droop and fall off, often all in a few weeks time
  • Occasionally, leaves can shrivel, turn brown and remain attached to branches for several weeks
  • When bark is peeled back, the inner bark is yellow brown and smells of wintergreen (American elm) or maple syrup (red elm)
  • Witches’ broom or dense leaf clusters at branch ends, common on red elms
  • Damage appears mid to late summer; infected trees die within a year or two
  • All Minnesota elm species are susceptible
  • More information on Elm yellows...
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  • Image: Armillaria root rot 1
  • Image: Armillaria root rot 2
  • Image: Armillaria root rot 3

Armillaria root rot
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 that can possibly be seen under the bark, around roots and in soil around the tree base
  • Wood is decayed, white, soft and spongy and 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
  • More information on Armillaria root rot...
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  • Image: Stem girdling roots 1
  • Image: Stem girdling roots 2
  • Image: Stem girdling roots 3

Stem girdling roots

  • Affected trees commonly exhibit excessive and abnormal winter damage including frost cracks and dieback
  • Affected trees are often stunted, exhibit poor summer color, change color and lose their leaves early in the fall
  • A root circling the trunk of the tree may be seen at the soil line
  • Trunk may become sunken in or compressed where it contacts the root
  • If girdling root is below ground, the trunk will lack the natural widening or flare at the soil line so will go straight into the earth like a telephone pole; trees often exhibit an abnormal lean
  • Affected trees commonly exhibit water-stress symptoms such as marginal leaf scorch, wilting, sudden leaf fall
  • More information on Stem girdling roots...

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