University of Maryland Extension

Dutch Elm Disease - Trees

Dutch elm disease symptoms
Dutch elm disease. Symptoms typically appear in May as wilted branches that show yellow then brown leaves

Key Points

  • Dutch elm disease is a serious lethal disease that infects a large number of elm species including American, winged, slippery, rock, and September elms.
  • Symptoms typically appear in May as wilted branches that show yellow, then brown, leaves.
  • Dried leaves may remain attached to the branches or may fall, leaving bare twigs.
  • As symptoms progress, entire limbs may show wilt symptoms and once the infection reaches the trunk the entire tree may wilt.
  • In older trees, wilt symptoms may progress throughout the canopy for several years before death occurs.
  • Infected twigs and branches typically show vascular streaking under the bark.
  • Management Strategies 

 flagging branches in a tree with Dutch elm disease
American elm tree showing typical 
flagging and dieback symptoms due to 
Dutch elm disease.
Photo: C. Kaiser, U. of KY,

beetle feeding

  • This fungal disease enters through feeding wounds made by the native elm bark beetle and the more prevalent, smaller, European elm bark beetle (see photo).
  • Beetles breed beneath the bark of dying or recently dead elms.
  • Infected or stressed trees actually emit an odor that attracts beetles to them for breeding and egg laying.
  • In addition, female beetles also emit attractants that lure additional beetles to declining trees.
  • There are up to three generations a year with the first emergence starting in April from overwintering larvae.
  • Beetles that emerge from infected trees typically are covered with fungal spores growing in the pupal chambers.
  • Beetles flying to other trees spread the spores to other trees.

Management strategies

  • The chief strategy for control of Dutch elm disease is through early removal of newly infected branches to interrupt the spread by elm bark beetles.
  • Ideally, removal should occur within two to three weeks after symptoms appear during the growing season.
  • Diseased wood should be chipped and removed from the site.
  • Pruning cuts should be made at a branch fork at least 10 feet below visible streaking in the sapwood.
  • Pruning will be most effective if less than five percent of the crown is affected.
  • High-value trees may be appropriately injected with systemic fungicides, administered by a licensed arborist. This is expensive and may need to be repeated in one to three seasons. If injections will be used, prune after the injections are complete.
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