DED is caused by a fungus that clogs the elm tree's water conducting system, causing the leaves to wilt and the tree to die, usually within one or two seasons. It doesn't infect other tree species.

The fungus is spread from one elm tree to another mainly by three species of elm bark beetle; the smaller European, banded and the native. The beetles breed under the bark of dead or dying elm wood. The new generation of beetles emerge from a diseased tree. Carrying the fungal spores with them, the beetles infest healthy elms on which they feed, thereby spreading the disease.

Photo of a European elm bark beetle
European elm bark beetle
J.R. Baker & S.B. Bambara, North Carolina State University, Bugwood.org
Banded elm bark beetle
Joseph Benzel, Colorado State University, Bugwood.org
Native elm bark beetle
Native elm bark beetle
J.R. Baker & S.B. Bambara, North Carolina State University, Bugwood.org

If beetles are present their emergence holes can sometimes be found on the bark. They are the size of the diameter of a pencil led, and you may find sawdust on the bark, indicated burrowing beetles. The beetles are an average of 3.0 mm in size.


Photo of a European elm bark beetle exit hole
European elm bark beetle exit hole
Joseph LaForest, University of Georgia, Bugwood.org

The characteristic pattern of the breeding galleries on the surface of the wood under the bark can also be used to identify these beetles. Smaller European elm bark beetle and  banded elm bark beetle galleries are single and run along the grain of the wood. Native elm bark beetle galleries are double and run across the grain.

Photo of a Native elm bark beetle gallery
Native elm bark beetle gallery
Joseph LaForest, University of Georgia, Bugwood.org
Photo of European elm bark beetle gallery
European elm bark beelte gallery
James Solomon, USDA Forest Service, Bugwood.org

It's illegal to transport, store or buy elm firewood. Firewood is one of the largest spreaders of DED; elm bark beetles on infected firewood hitch a free ride with unsuspecting campers and homeowners, spreading the disease.

  • Don't transport firewood when camping;
  • Avoid elm when cutting or buying firewood;
  • Don't store pruned elmwood to burn in a fireplace later.

Resources

Dutch elm disease prevention/control measures: responsibilities and authority Under the Agricultural Pest Act

Contact

For information about STOPDED or Dutch elm disease call the STOPDED Hotline at: 1-877-837-ELMS (3567)