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Oak Wilt
Root Graft Disruption
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| Root graft disruption is an important means of controlling
oak wilt. A combination of trenching and treating with Macro-Infusion
of Alamo will save more trees than trenching alone. The
most commonly used equipment for trenching is a trenching machine,
rock saw, or a vibratory plow. |
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Success Is Variable
Success with breaking root grafts has been variable and is not always
possible because of factors present on the site. These factors include
utilities, slopes, and objects that block the equipment from cutting
all the roots, such as: slab house foundations, rocks, or other
tress. Also, because the depth of the trenching equipment can be
limited, you can have situations where the roots are growing deeper
than the trenching equipment can cut. This is most often the case
in porous soils such as sand or rock aggregate. When disrupting
roots in these soils, as low as 60% success has been reported. Other
less porous soils show much higher success with trenching to disrupt
root grafts. This is because roots will not grow deeper than a ready
supply of oxygen is available.
The Purpose of Trenching
The purpose of trenching is to disrupt the root grafts that
connect diseased trees to healthy trees. Of course it is difficult
to know exactly where the Oak Wilt fungus lies within the
vascular system of a tree, so a conservative approach must
be used. Trees that show symptoms of oak wilt must be physically
isolated from nearby symptom free trees. If the trench is
in place before the fungus has spread past the trench then
the adjacent trees will not be infected through root graft.
If the disease has already traveled through the root system
past the place where the trench was dug then the disease has
not been contained.
 Other
Information
Trenches are typically installed 50– 100 feet from the infected
tree to insure that the disease has not entered the roots
being cut. This often means cutting outside trees that are
not showing symptoms. These trees not showing symptoms that
are close to the infected tree are the best candidates for Alamo macro-infusion. If
using a trenching method that removes the soil from the trench,
it can be backfilled immediately.
Research shows that root grafts
will generally reform after 4 – 5 years. However, both trees
must be actively growing for roots to regraft. Thus, trees
that died from Oak wilt will not regraft to healthy trees.
The Oak Wilt fungus is capable of residing
in the root system of dead trees for 3-4 years.
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