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Issue link: http://read.dmtmag.com/i/479845
40 April 2015 Landscape and Irrigation www.landscapeirrigation.com Plant HealtH Care LI are the ones caused by excessive or misplaced injection pressure and the injuries resulting from chemicals of treatments themselves. There are devices that, instead of drilling a clean hole, use a gouge to remove a small piece of bark. A rubber valve is inserted into the hole and small volumes of treatment solution are squeezed into the valve and presumably into the vascular tissue. The downside of this type of treatment method is the pressure from the injection can build up right under the bark, causing the bark to separate and an air pocket develops. The tissue under the bark then dies, leaving large wounds under the bark that a tree cannot compartmentalize, which leads to the spread of decay. Wounds related to the chemical formulations are, unfortunately, quite common as well. Often, it is not the active ingredient that is causing the damage, it is the inert ingredients, the carriers that are used to formulate these treatments. Many types of tree treatment chemistries are not soluble in water so they are suspended in solvent-based solutions. Other times, solvents and other alcohols are added as preservatives or buffers. These formulations are necessary to allow the treatments to get to market in liquid form to be injected into the tree, but can also have a detrimental drying effect that damages the cells of the tree. HOW TO MINIMIZE WOUNDING No matter how they are marketed, all forms of tree injection treatments will cause damage to the tree, so what are the ways we can minimize the wounding to the tree? First, use sharp drill bits. Our tree care company preforms between 6,000 and 8,000 tree injection treatments each year, and we replace the drill bit every fi ve to seven trees. Sure there is a cost to the drill bits, about $5 each for razor-sharp high-helix bits, but the benefi ts in faster injection time and effectiveness of the treatments outweigh the costs. Second would be injecting into the root fl ares versus into the trunk tissue. We haven't talked about root fl ares to this point, but they play a key role in proper tree injection. Vascular tissue is thicker in the root fl ares than up in the trunk, which allows greater area for the treatment to move into, and root fl are tissue has high meristematic activity as well. This means injection site wounds on the root fl ares compartmentalize much faster than the same holes would on the trunk. Third, do not go higher than the recommended pressure for the device you are using. Devices vary widely in their recommended psi, from about 15 to 20 psi on the low end, to nearly 200 psi on the high end. A common misconception is that high pressure results in faster treatment uptake — it doesn't. In fact, cranking up the pressure often slows the process down. Think of a 2-liter pop bottle fi lled with water. As pressure increases inside the bottle, the water will come out of the mouth of the bottle faster, until you hit a pressure where the mouth of the bottle is not big enough so the water doesn't come out any faster. Follow the device's guidelines to avoid slowing down the treatment or damaging the tree. Fourth, select chemistries that will not damage tree tissue. How do you know which ones those are? Good question. No one really knows, in fact. EPA labeling looks at effi cacy and environmental/human health risks, but the effects on the trees are not part of their evaluation criteria. In general, look for treatments that are diluted or packaged in water-based solutions; but even that can be diffi cult to determine. So, don't be shy about inquiring about the chemical makeup of these products from your manufacturer or distributor reps. Fifth, ask if it really needs to be injected. Some insect and disease issues can only be treated with injection applications, but many have other options as well. If a soil application or even a well-timed spray can do the job, you can avoid wounding the tree all together. If an injection must be performed, utilize chemistries that offer multiple years of protection to avoid wounding the tree on an annual basis. Giving the tree time in between treatments will greatly lessen the impact of tree injection wounding. TOWARD A UNIFIED TREE INJECTION THEORY You may be wondering, with all the interest in tree injection these days, coupled with the amount of confusing or even contradictory information surrounding it, is there an industry standard to which we can turn? Luckily, the answer soon will be yes. A Tree Injection Best Management Practices (BMP) guide has been in the works for several years now, and is expected to be available in 2015. The BMP will go a long way toward standardizing the application protocols and, hopefully, clear up many of the gray areas. Tree injection wounding has many other aspects we have not had time to discuss, such as the impact of using plastic plugs in the holes or what the long-term effects of multiple injections might be. For now, we'll leave it at yes, tree injection causes wounding, but yes, there are steps you can take to minimize the impacts to the tree. Every injection scenario should be approached with an understanding of why it needs to be performed and how to properly do it. Maybe we'll work some phrasing about this into our Arborcratic Oath… Brandon M. Gallagher Watson is creative director at Rainbow Treecare Scientifi c Advancements, and is an ISA Certifi ed Arborist (#MN-4086A). Root fl ares are recommended for injections. IMAGE COURTESY OF RAINBOW TREECARE SCIENTIFIC ADVANCEMENTS