|
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.
Physical Breaking of Roots
The only way to stop the spread of Dutch Elm disease through
root grafts is by physically breaking the root connections
between the infected tree and the healthy tree.
This is most often accomplished with trenchers or vibratory
plows. In situations where there are buried utilities, an
Air Spade™ or AirKnife™ can be used to remove the
soil and expose the root grafts without damaging the utility
lines. Trenches should be at least 3’ deep in clay soils
and 5’ in sandy soils, although it is always best to
go as deep as your equipment allows.
Install Trenches Midway Between Infected
and Healthy Tree
Trenches are typically installed midway between the infected
tree and the healthy tree, although this can be adjusted in
either direction depending on how far the infection has spread.
It is important to know where the Dutch elm disease fungus is located in the
diseased tree before the trench is installed. If the disease
stain is already at ground level in the infected tree it is
impossible to determine how far it has traveled through the
root system toward the healthy tree, so a second trench may
be necessary. This trench would isolate the healthy appearing
tree from any others that might be root grafted to it.
Sever The Root Grafts Before Removing
the Infected Tree
It is important to sever the root grafts before removing the
diseased tree. Because each tree is transpiring, removal of
the diseased tree will allow the healthy tree to pull all
of the moisture and fungal inoculum out of the other tree’s
root system quickly. |
 |
 An
airspade can be used to remove soil and expose root grafts
in situations where utilities are present |
 |
 |
| Elms
that grow close to each other (Canopies touching) are
often root grafted |
|
