What is Dutch Elm Disease?
Dutch Elm Disease is a fungus called Ophiostoma Novo-ulmi.
This fungus grows only in elms. Most species of elms are susceptible
including, American, Slippery (red), English, European, and Winged.
Less susceptible species include Siberian, Chinese, and Cedar elms.
The disease is spread from sick trees to healthy trees most commonly
on the elm bark beetle Scolytus multistriatus. It can also
pass from one tree to another through root
grafts, a situation where a tree's roots fuse underground with
another tree of the same species.
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 Tracing
can save elms if done in the initial stages of the disease.
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Fungal Growth Inside The Elm
The fungus that causes Dutch elm disease is not a blight or a wood
decaying organism. Instead it lives inside the xylem of a susceptible
elm. Understanding the fungus growth pattern is important to knowing
if a sick elm can be saved and for understanding the process of
tracing, a method where an arborist creates a physical separation
of the fungus from the elm.
Beetle infections generally start in the 2 - 4 year old twigs.
This is where the beetle feeds and mates. The fungus rubs off the
beetle and begins to grow in the tree. The fungus grows in a very
predictable pattern. Usually it stays narrow in width and grows
down the branch. It will enter the stem of the tree and grow in
this narrow line to the roots. Once the fungus enters the root flares,
the fungus will grow sideways and back up the tree in many places.
Tracing can save elms if the initial infection is caught before
entering the roots.
A characteristic stain on the xylem of an elm infected with Dutch
elm disease is caused by the tree producing gum like substances
called tyloses in an attempt to stop the spread of the disease.
These tyloses actually are what cause the tree to wilt and die as
they block the xylem and prevent water transport to the top of the
tree. So in effect the fungus stimulates the elm to kill itself.
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| Macro-Infusion
of Arbotect protects healthy Elms for 3 growing seasons. |
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