(Ophiostoma ulmi or Ceratocystis ulmi)

Photo 39: Natural Resources Canada

Biology

• 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

Photo 40: Beat Forster, Swiss Federal Institute for Forest, Snow and Landscape Research, Bugwood.org

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

Impact on Trees

• there are three native species of elm in Canada and all have been affected to varying degrees by Dutch elm disease
• the greatest impact has been on American Elm (Ulmus americana) and Rock Elm (Ulmus thomasii)
• Red or Slippery Elm (Ulmus rubra) is least affected by the disease

Control

• 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

Links

• Saskatchewan Dutch Elm Disease Association. (http://www.sdeda.ca/)
• Dutch Elm Disease. Alberta Department of Agriculture and Food. (http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/prm1043)
• Manitoba Conservation Forestry Branch. Dutch Elm Disease. (http://www.gov.mb.ca/conservation/forestry/forest-urban/u-faq.html)
• Field Guide to Tree Diseases of Ontario. Dutch Elm Disease. Natural Resources Canada. (http://cfs.nrcan.gc.ca/subsite/glfc-treedisease/ophiostoma-ulmi/4)
• Wikipedia, the free encyclopedia. (http://en.wikipedia.org/wiki/Dutch_elm_disease)
• Three American Tragedies: Chestnut Blight, Butternut Canker, and Dutch Elm Disease. Scott E. Schlarbaum, Frederick Hebard, Pauline C. Spaine, and Joseph C. Kamalay. Report available at: (http://www.srs.fs.usda.gov/pubs/ja/ja_schlarbaum002.htm)