Tree Killers: Dutch Elm Disease

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  • Common English name: Dutch Elm Disease
  • Other names: “DED”
  • Latin (scientific) name: Ophiostoma ulmi or Ceratocystis ulmi

Threat type

150x150 diseases

History in Canada

  • lumber infected with the fungus arrived in North America about 1930
  • the disease reached Eastern Canada in the 1940’s
  • it arrived in Manitoba in 1975 and Saskatchewan in 1981
  • the disease does not occur in Alberta or British Columbia where American Elms were planted beyond their natural range (Saskatchewan to Nova Scotia)
  • the majority of elms in Eastern Canada died of the disease in the 1970’s and 1980’s
  • scattered healthy trees, generally young, do still occur in the east


  • Dutch elm disease is a fungal disease of elms
  • the fungus is spread by both a native and an introduced bark beetle whose larvae tunnel under the outer bark and create distinctive feeding ‘galleries’
  • the adult beetles are very small (2-3 mm or 1/8 in)
  • the first signs of the disease are upper branches dying and leaves turning yellow in mid-summer
  • gradually, the damage spreads to the rest of the tree which eventually dies
  • some trees will resprout from the base and the sprouts may live for a number of years

Impact on Trees

What can be done to control this tree killer?

  • There are fungicide treatments available for individual trees but they are costly,
  • must be repeated regularly, and may only prolong the life of the treated tree by 5-10 years
  • in the early stages of the disease, infected branches may be pruned and destroyed
  • selection programs are ongoing to find and distribute resistant trees and several cultivars are presently available
  • hybridization studies are also underway to find trees not susceptible to the fungus
  • it will be many years before most of these cultivars or hybrids reach maturity and prove their resistance to the disease

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