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Elm > Leaves > Leaves on a portion of the branches turn yellow

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  • Image: Dutch elm disease 1
    Credit: M. Grabowski, University of Minnesota
  • Image: Dutch elm disease 2

    Credit: M. Grabowski, University of Minnesota

  • Image: Dutch elm disease 3

    Credit: M. Grabowski, University of Minnesota

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green arrowDutch elm disease
Ophiostoma ulmi and Ophiostoma novo-ulmi

  • Initial infection occurs on one branch; disease may quickly progress to all branches
  • Leaves turn yellow, wilt or shrivel, turn brown, then fall off the branch
  • 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: Botryodiplodia canker 1
    Credit: Barnard, Bugwood.org
  • Image: Botryodiplodia canker 2

    Credit: W. Jacobi, CO State University, Bugwood.org

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green arrowBotryodiplodia canker
Botryodiplodia ulmicola

  • Leaves growing beyond the canker turn yellow and wilt (Siberian elm) or fall off (American elm)
  • Clumps of adventitious sprouts or shoots develop below cankers on large branches
  • Reddish brown to black water soaked cankers form on branches 4 inches in diameter or smaller
  • Sap wood underneath the canker is reddish brown
  • Tiny raised pimple like fungal structures form on branches killed by the canker, causing bark to look rough
  • Damage is most severe on trees stressed by other factors
  • More information on Botryodiplodia canker...
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  • Image: Oystershell scale 1
    Credit: W. Seidel, University of Minnesota
  • Image: Oystershell scale 2

    Credit: W. Seidel, University of Minnesota

  • Image: Oystershell scale 3

    Credit: W. Seidel, University of Minnesota

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green arrowOystershell scale
Lepidosaphes ulmi

  • Feeding can cause foliage to yellow
  • Twig and branch dieback can occur when branches are heavily infested
  • Light to dark brown, elongated, 1/10 to 1/8 inch long, found feeding on branches
  • Heavy infestations can completely cover bark
  • Damage occurs during summer
  • More information on Oystershell scale...
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  • Image: European elm scale 1
    Credit: W. Cranshaw, Colorado State University, Bugwood.org
  • Image: European elm scale 2

    Credit: J. Hahn, University of Minnesota

  • Image: European elm scale 3

    Credit: J. O'Brien, USDA Forest Service, Bugwood.org

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green arrowEuropean elm scale
Gossyparia spuria

  • Yellow leaves on lower branches
  • Heavy infestations cause premature leaf drop and dieback of branches
  • Excrete honeydew so leaves and branches may be covered by sooty mold
  • Dark gray oval body outlined by white wax
  • Found mainly on American and rock elm
  • More information on European elm scale...
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  • Image: Verticillium wilt 1
    Credit: USDA Forest Service Archive, USDA Forest Service, Bugwood.org
  • Image: Verticillium wilt 2

    Credit: J. O'Brien, USDA Forest Service, Bugwood.org

  • Image: Verticillium wilt 3

    Credit: W. Jacobi, Colorado State University, Bugwood.org

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green arrowVerticillium wilt
Verticillium dahliae

  • Leaves are small and yellowed in chronic infections
  • Leaves turn brown from the edges and tips, wilt and die in severe infections
  • Leaf symptoms are often seen on only one branch in the canopy
  • Dark brown to black streaks often can be seen in the sapwood if the bark is peeled back, appearing as rings or arcs in a cross cut
  • Symptoms may develop over a single growing season, or over several years
  • More information on Verticillium wilt...
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  • Image: Stem girdling roots 1
    Credit: M. Grabowski, University of Minnesota
  • Image: Stem girdling roots 2

    Credit: G. Johnson, University of Minnesota

  • Image: Stem girdling roots 3

    Credit: J. Tilden, Tree Care Advisor

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green arrowStem girdling roots

  • Affected trees are often stunted, exhibit poor summer color, change color and lose their leaves early in the fall
  • Affected trees commonly exhibit excessive and abnormal winter damage including frost cracks and dieback
  • 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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