How DED is Spread?

In Manitoba, Dutch elm disease is most commonly spread by native elm bark beetles. The adult beetles are tiny (two to three mm) and dark brown and are difficult to see.

native elm bark beetle.

They breed in dead and dying elm material. Beetles emerging from brood trees that were infected with Dutch elm disease can be contaminated with the spores of the Dutch elm disease fungus. When these beetles move to other elms to feed or over-winter under the bark at the base of an elm, they can infect healthy elms. Dutch elm disease may also be spread from tree to tree if the roots of an infected tree are touching the roots of a healthy tree.