I was fortunate to discuss this dilemma with two Plant Pathologist from Australia, one in Italy, and one in Germany and none had too many favorable comments about below soil injection. They explain the logic and reality of trunk stem injection, in simple terms of getting the job out of the dirt, away from soil borne pathogens, insect invasion, canker infections, reducing the drill size and number of drill portals and much faster wound closure. Equally important was the uptake from trunk stem injection, it achieved greater efficiency and distribution throughout the tree's canopy, as it is beginning of the constricted bottleneck of the upper trunk stem. In Oak trees the water movement is at the rate of 92 feet per hour and therefore, providing a thorough and a very rapid chemical distribution, with minimum overall damage to the tree. The one most important factor is that wound closure is much faster and more efficient up the trunk stem extending from above the trunk base to upper branches as it is associated with stem growth and the annual increase stem diameter. Meristem cells (similar to stem cells in humans) display an important role in regeneration and wound closure ... and the tissue layer known as cambium.....

The Chemjet Injector Syringe, (Australian made) one of the best micro injection systems that is now available on the market. Chemjet® has more that twenty five years of field application and is used worldwide. The injector can be filled to 5,10, 15,and 20 mils providing a more accurate prescription application. It is a re-usable, spring loaded syringe which is very practical, and unlike the pre-filled injection capsules, are one time use disposable products. The Chemjet® can be re-used 1000 times with proper care and handling.

The Chemjets, delivers the same prescribed volume of the fungicide ( Propiconazole 14.3 % MEC ) at the preventive rate of 10 mils per diameter inch, in a 50% concentrated solution measured at 20 mils per injector and placed 3" apart around the tree above the trunk flare. Unlike the macro injection system, with a very high volume water at the rate of 10 mils of fungicide diluted per liter of water. Often times, the tree will not absorb the full prescribed amount of fungicide / water solution, leaving as much as a 1/3 or more of the product in the tank. The Chemjet procedure with the higher concentration is much like a booster shot of an antibiotic, only with far more effective results, as the application uses the water within the tree for dilution and transport to the leaves and distribution throughout the entire tree. The damage factor with the Chemjets, are far less invasive and the wound closure, due to the small shallow holes 11/64" will close within a few short weeks. The macro drill size 5/16"takes a longer time for closure partly due to the dirt at the drill sites. Excessive damage to the trunk flares, limits the water and nutrient movement to and from the roots and can rob the tree from vigor, good health or cause eventual death.

The most rapid movement of water is up through the trunk stem from the roots to the canopy. Concluding, the trunk stem is the most effective location for injection sites, maximizing uptake and distribution, and at the same time minimizing wound effects, pathogenic infection and all the while protecting the ENVIRONMENT.

After more than a year, I am satisfied with the performance of the Chemjet Tree Injectors. They provide very efficient delivery, minimal wounding, protective of the environment and very labor saving. The chemjet® is reusable, and is used worldwide for more than 25 years on annual injections and the trees continue to prosper showing vigor and good health.

IMPORTANT NEWS  - More than 40 years of suppressed research !

Trunk Stem Injection / Infusion

Trunk stem injection / infusion was the first injection method used, probably because it was convenient for the applicator. It was found to be problematic in Dutch Elm Disease because injection ports were deep, ( penetrating several growth layers or sap wood ), uptake was not guaranteed and the ideal sink was often missed.  Injection ports were later developed and applied a shallow-pit trunk injection technique in which fungicides were pressure injected into very shallow drill injection ports of the three outer most growth rings. This technique found high comparability in the translocation uptake relative to root flare injection method as water movement is very rapid up the trunk stem which, moves at the rate of 92 feet per hour. 
 

Although wound closure of the shallow portals that are drilled in the trunk stem 4.5 ft above the soil level was relatively quick within 6-8 weeks. However, clients often objected to the visible, large, open injection ports which were 1/2 in diameter placed 3-5 inches around the trunk stem. Thus, it was concluded that the next best injection site would be the root flares 4-5 inches below soil level which, indeed, has become the chosen technique and standard site for tree injection. This was ideal, as it quelled the client from any further objection since the damage was no longer visible and also the extent of damage was totally out of sight as well. It was not important to research the uptake, the damage factor nor the effects of microorganisms, pathogenic infections and eventual decay at the injection sites, as it's only purpose was to appease the objections from the customer.

 

The drill port !  Is actually 1 inch  scale - I----------I     

I---------------I   The 1" shallow pit port.     Later comes the 1/2" O portal and  years later, it was reduced to the 5/16" dia.  Now, imagine these gapping holes all around the trunk stem.  It was sure best to hide something like that, all for the benefit of science!