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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous Trees > Elm > Dead branches or branch dieback

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Elm > Trunk/Branches > Dead branches or branch dieback

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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: Native elm bark beetle 1
  • Image: Native elm bark beetle 2
  • Image: Native elm bark beetle 3

Native elm bark beetle
Hylurgopinus rufipes

  • Egg galleries extend against grain, noticeable when bark is removed
  • Little or no damage to tree unless beetle is carrying Dutch elm disease fungal spores
  • Adults are 3/32 inch long; brownish black
  • All elm species in Minnesota are attacked
  • More information on Native elm bark beetle...
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  • Image: European elm bark beetle 1
  • Image: European elm bark beetle 2
  • Image: European elm bark beetle 3

European elm bark beetle
Scolytus multistriatus

  • Feed at the twig crotches, girdle the bark, cause small branches to fall off
  • Egg galleries extend with the grain, noticeable when bark is removed
  • Little or no damage to tree unless beetle is carrying Dutch elm disease fungal spores
  • Adults are 1/8 inch long; shiny, dark reddish brown to black
  • All elm species in Minnesota are attacked
  • More information on European elm bark beetle...
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  • Image: Botryodiplodia canker 1
  • Image: Botryodiplodia canker 2

Botryodiplodia canker
Botryodiplodia ulmicola

  • Reddish brown to black water soaked cankers form on branches 4 inches in diameter or smaller
  • Sap wood underneath the canker is reddish brown
  • 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
  • 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: Verticillium wilt 1
  • Image: Verticillium wilt 2
  • Image: Verticillium wilt 3

Verticillium wilt
Verticillium dahliae

  • Leaves turn brown from the edges and tips, wilt and die in severe infections
  • Leaf symptoms are often seen on only one or a few random branches in the canopy
  • Leaves are small and yellowed in chronic infections
  • 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: Lightning injury 1
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Lightning injury

  • Continuous, sporadic or twisting, vertical stripping from bark torn away on main stem or other large branches
  • Cracks or splits in bark from lightning strikes begin in the canopy and extend to the ground line
  • Often, large pieces of wood strewn about the hit tree
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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
  • 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 are often stunted, exhibit poor summer color, change color and lose their leaves early in the fall
  • 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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  • Image: Oystershell scale 1
  • Image: Oystershell scale 2
  • Image: Oystershell scale 3

Oystershell scale
Lepidosaphes ulmi

  • Twig and branch dieback can occur when branches are heavily infested
  • Feeding can cause foliage to yellow
  • 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
  • Image: European elm scale 2

European elm scale
Gossyparia spuria

  • Heavy infestations cause premature leaf drop and dieback of branches
  • Yellow leaves on lower 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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