Tree Biology notes -
Injecting into a tree requires a drill and the penetration of the protective bark, the drill holes are spaced around the tree and chemical is then injected with measured injectors. This treatment is a great way to deliver a chemical quickly and efficiently into the trees vascular system, results are good and chemical use is less than with other methods.
The downside is the drill holes, there is nothing 'micro' about them, they are at least 4mm diameter and depending on species and age could be more than 4cm deep. Each treatment (every 2 - 5yrs for Elm Leaf Beetle) requires a new set of drill holes. A tree will usually callus (but not heal) over drill holes within a few years, particularly younger healther trees. This covering of the wound is good from an aesthetic perspective however the damage remains inside. The holes are an entry point for decay casuing pathogens, also the tree will actively shut the area around the wound down, ceasing to function in that area. Over many years the number of holes will impact plant function.
The degree of impact will depend on a number of factors, if a tree is old and stressed possibly in a cool climate, it will be less able to deal with pathogens, less able to compartmentalize decay, less able to callus over. A young fast growing tree in Queensland such as an avacado will quickly callus over and put on new conductive tissue.
For these reasons our approach to Stem injection for any pest or disease (including Elm Leaf Beetle) is that stem injections should only be used in certain circumstances; for example the tree is going to be removed in the short to medium term or it is not possible to use other control methods. Some companies are now doing more stem injections, though this may (not 'will', just 'may') give better Elm Leaf Beetle control in the short term, long term it will cause permanent damage and possibly significant decay within the trunk.
Sometimes it may be appropriate to use stem injection if there is an infestation and it is getting late in the year for soil injection.
Principles of Modern Arboricultural Management.
Proper urban tree management is based on
a sound understanding of tree biology that
informs arboricultural practice (Moore 2004).
There are basic principles of tree biology that
are the foundations of modern arboricultural
practice, and these are of greater significance
when the trees concerned are either stressed
or aged (Table 1). These principles must
be considered when putting tree injection
processes in context.
Under these principles tree injection must be
seen as an invasive process that inevitably
wounds the specimen involved. Accordingly,
the injections should only be used when
other techniques have failed and should
be seen as a measure of last resort for pest
control or the improvement of tree health.
With old or stressed trees there is a real
risk that tree injection may actually make
things worse for the specimen that you
are hoping to treat, which is contrary to
the principles of modern arboriculture.
Consequently, tree injections must be seen
as a part of a comprehensive pest control or
tree management program. It should only be
used when other measures have failed and
when the benefits of injection can be shown
to outweigh the risks to tree structure,
vigour and health.
Phone: 03 8644 8005
Below is an image from a chemical trial / field study showing the extent of impact from a small drill hole after just 4 months. It is incorrectly labeled as 'nicely compartmentalized'
The discolouration is a chemical reaction within the tree. After only 4 months, reaction is seen from the drill hole at the bottom red arrow to the top arrow. Over time decay can spread throughout a trunk reducing structural integrity.
Tree age, water stress and other factors can increase the degree of damage as will ongoing defoliation by Elm Leaf Beetle.
Treetec will undertake stem injection if there is not a more appropriate method available.
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