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Dutch Elm Disease: Cause and
Prevention
How Dutch Elm Disease spreads
- The Dutch elm disease fungus can infect a tree in two ways. The
most common method of transmission is on the bodies of elm bark
beetles. The fungus also spreads from diseased to healthy trees
through grafted roots.
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An elm bark beetle's life revolves around elm trees. It breeds in
dead and dying elms, and depends exclusively on elm tissue for food
creating a devastating cycle for elms when the Dutch elm disease
fungus Ophiostoma novi-ulmi is thrown into the mix. The adult
females in one piece of wood the size of a fireplace log can lay
thousands of eggs.
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If the tree died from Dutch elm disease, every beetle that
hatches and emerges as an adult from that wood may be carrying the
fungus. They will be looking for a healthy elm on which to feed and
will inadvertently inoculate the tree with Dutch elm disease via the
spores carried on their bodies. The majority of new infections, and
the bulk of the losses to Dutch elm disease are due to this method
of transmission. That is why prompt detection, removal, and
destruction of dying elms are so critically important.
- The other method of disease transmission between elms is through
grafted roots. When elms are growing near each other, their roots
come in contact in the soil and graft together. In the absence of a
vascular wilt like Dutch elm disease, this is an advantage for the
trees. The Dutch elm disease fungus, however, can pass from diseased
to healthy trees through these grafted roots and continue to spread
indefinitely through a stand of elms.
Dutch Elm disease symptoms
- The first evidence of Dutch elm disease is wilting or "flagging"
in one or more of the branches, usually starting in the outer
portion of the crown. Leaves on the infected branches turn dull
green to yellow and curl, finally becoming dry, brittle, and brown.
The symptoms progress down the limb and eventually throughout the
entire tree. Trees infected through root grafts can die very
rapidly, while trees infected via the feeding of bark beetles can
take several years to die.
- Another symptom of the disease is the discoloration of the water
conducting vessels. Peeling the bark off infected wood, revealing
the staining, easily sees this.
Managing Dutch Elm disease
- Dutch elm disease is difficult to control. However, with a
properly implemented program, the devastating effects of the disease
can be greatly reduced. An effective program includes three parts:
prompt detection and removal of diseased elms, disruption of
transmission through common roots, and protection of valuable elms
through proper injection procedures.
Sanitation
- Sanitation is the key to effectively managing Dutch elm disease
on a community wide basis. It involves identifying diseased elms,
and prompt removal of these trees. This may prevent root graft
transmission and definitely will reduce the number of disease
carrying beetles. A single dead elm can produce tens of thousands of
contaminated beetles. Without such a program, a substantial majority
of a community's elm population will die within a few years.
How can Emerald Tree Care help?
- Have one of our ISA Certified Arborists visit your property to
perform a thorough inspection and evaluation of your property and
provide you with our Three Year Elm Tree Inoculation Program.
- This program boasts a 95% success rate in Dutch Elm Disease
prevention and will assuredly work for you in the preservation of
these marvelous and majestic shade trees.
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