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Elm Disease |
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Question
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Is Dutch elm
disease a problem in Texas?
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| Answer |
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From what I can gather, there
is an extremely low incidence of DED in Texas. I was told that there is usually at least one confirmed case a year
in Texas, but there has been no significant wholesale loss of elms due to DED.
The native Cedar elm seems to display some level of resistance to DED but
I do not believe that this has been extensively tested. The American elm
is not a prevalent species in the state.
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| Question |
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How long can Dutch elm disease remain dormant
in elm trees? |
| Answer |
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I found out that in one study, the researchers isolated the fungus in vessels
in the tree that had been effectively sealed off in the tree for 25
years. The fungus that was isolated was still viable. If this occurs in trees it
is generally not a threat to survival if the defense reactions
effectively isolate the disease by the end of the growing season.
If, however, the defense reactions are not complete, the fungus may be able to reach
the newly forming vessels in the next growing season. When this happens
there is a much higher likelihood that the disease will affect the entire tree
and eventually kill it.
I must point out that this is not a
common occurrence.
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| Question |
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My Siberian
elms died. I don't think it was Dutch elm disease and I want to
use the wood for furniture. Is it safe? |
| Answer |
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Generally,
DED does not kill Siberian elm trees. Usually only one branch
will die as the species can
effectively fend off the disease. I would be fairly
certain that your trees are not infected with DED. If you remove
all of the bark there should be no risk of bark beetles breeding
in the wood. You should check with the local authorities, however,
as there may be bylaws restricting the use of elm wood.
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| Question |
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Are some elm species more
resistant to Dutch elm disease than others? |
| Answer |
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Yes. Species that have
coexisted with the Dutch elm disease fungus for the longest period tend
to have the highest degree of resistance. These species have
evolved to develop better defenses against the pathogen.
Scientists now believe that Dutch elm disease originated in central
Asia. Therefore, we would expect that species originating from
Asia would show an increased resistance to DED and in fact that is what
we do see. The Siberian elm, for example, is largely
resistant. Species such as the American elm, however, have only
recently come into contact with the disease and as such have not had the
time to develop immunity.
Scientists are now working towards
developing cultivars which exhibit greater resistance to Dutch elm
disease. The Liberty Elm is one such cultivar.
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| Question |
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I have heard
of an antifungal called Nystatin. Can it be used to treat Dutch
elm disease? |
| Answer |
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Because Nystatin
is an antifungal, it could conceivably have an effect on Dutch elm
disease. The drug was, however, designed for use on humans and is
relatively expensive to procure. A major concern about the use of
Nystatin arises from the fact that it is an antibiotic. As a
result, overuse can lead to more aggressive strains of the fungus. |
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