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38 April 2015 Landscape and Irrigation www.landscapeirrigation.com Plant HealtH Care Tree Injection Wounding: The Hole Truth Upon receiving their doctorate of medicine, physicians often vow to Primum non nocere, a Latin phrase meaning "First, do no harm." Whether this phrase is originally in the Hippocratic Oath or added later is a matter of historical debate, but the meaning of the phrase permeates modern medicine, and is part of the trust system we have with doctors. We trust that when we need medical assistance, the doctors are not going to hurt us on their way to healing us. While this is a great mantra for the medical industry, there are plenty of cases one could argue that harm is being done on the way to healing. Surgery is an obvious example, same with chemotherapy, the side effects of certain medications, or even the needle from an intravenous injection. All of these would seemingly violate the "fi rst, do no harm" credo, so how does a doctor reconcile this? I'm not a doctor, but I'd guess they do it by the same risk/ reward math we use on everything else. Sure, chemo is terrible, but cancer is more terrible. Sure, a shot wounds the body, but mumps would wound the body more. In all these cases, the doctor weighed the effects of his or her actions against the effects of non-action. Arborists, as the doctors for trees, also do this type of decision making. We know that any action that wounds the tree should be done with intentionality and a clear understanding of the effects. If we defi ne "tree wounding" as "a mechanical injury that disrupts or divides living tissue," there are many ways trees are wounded. Pruning, for example, is a form of tree wounding, so is tapping maple trees to produce its delicious syrup. Interestingly, there seems to be little controversy over these types of wounding practices. I have never heard an arborist say they refuse maple syrup on ethical grounds, but I have heard arborists say they refuse to perform tree injections because they can't justify drilling the tree. These same arborists own chain saws and regularly prune living trees; but I digress. This was not meant to be an "ethics of tree injection" tangent, we'll put that debate aside and look at the facts of wounding as they are. TYPES OF WOUNDING FROM TREE INJECTION When discussing wounding from tree injection, we think most often about the drill hole. As this is the one type of injury we can see, and the one on which the applicator has a strong infl uence, it is good to think about how this affects the tree. Injury from drilling can be impacted BY BRANDON M. GALLAGHER WATSON Proper drill depth avoids unnecessary wounding. The benefi ts of tree injection must outweigh the wounding. PHOTOS ON THIS PAGE COURTESY OF RAINBOW TREECARE SCIENTIFIC ADVANCEMENTS Sharp high helix drill bits can minimize wounding impacts. The recommended depth for tree injections is 3/4 inch to 1 inch past the bark.