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Issue link: https://read.dmtmag.com/i/96774
Despite these advantages, tree injection remains a mystery to some, and even controversial to others.There are some disadvantages, of course — with tree wounding and application time at the top of that list — and injection is certainly not a "silver bullet" for every tree problem. Adding to the confusion, a bevy of devices are available to you these days from manufacturers that all claim to have benefits over the others. So how does one know which devices to buy, and in which situations to deploy them? Tree injection systems and methods Tree injection can be loosely defined as any method by which a solution is introduced directly into the vascular system of the tree, but there are many ways this can be accomplished. There are passive injection systems, by which a bag of solution is hung on a tree and a series of tubing and tees delivers it by gravity into holes drilled in the base of the tree. As far as the science of tree injection is concerned, these passive methods work just fine for getting treatments into a tree, but the business of tree injection also requires treatments to be applied quickly as labor costs are often the largest expense of this method. This is one of the reasons that the vast majority of tree injection devices utilize pressure to move treatments into the tree. Depending on the device, this pressure can range from 8 psi upward to 60-70 psi. Pressure is not the only factor that influences uptake time for an injection treatment. The species of tree has a significant impact, with some trees — such as elm and oak — taking the treatments fairly quickly, while others — such as red maple or white birch — are known to be notoriously slow. The time of year, recent weather, and any tree stress prior to treatment will all influence the time it takes to get a full dose into the tree. An easy fact to remember is that our tree injection treatments are going into the current year's growth ring, so anything that would cause smaller growth rings — such as drought or stress from an insect attack — will have an influence on a treatment's uptake. The vast majority of today's tree injection techniques are lumped into either macro- or micro-injection. The difference www.landscapeirrigation.com Macro injection using a manual pump. between the two simply comes down to the volume of solution that will be introduced in the tree. Although these terms are not official by any means, in general, "micro" refers to volumes of milliliters up to a few liters of solution while "macro" implies the application of a few to several dozen gallons of solution. (As an aside, the term "infusion" versus "injection" can be confusing, but the terms can be used interchangeably. Technically, none of the treatments we apply to trees are "infusions;" they are all "injections." I believe "infusion" sounds softer so it is frequently used by marketers, but don't let it trip you up.) Micro-injectors come in many shapes and sizes. There are pre-filled capsules, as well as refillable capsules. Some applications simply require drilling a hole, inserting a capsule, and waiting for the capsule to empty. Pre-filled capsules have a historical complaint of unpredictable uptake time — some may empty in a matter of minutes, others may be several hours — causing scheduling nightmares for tree care professionals. Another downside is disposing of empty capsules; but in terms of fast set-up and ease-of-use, the pre-filled capsules are hard to beat. More elaborate micro-injection systems may use a small bottle as a reservoir and then employ a series of tubes and needles to move the treatment into the tree. These systems often require a plug inserted into the hole to prevent the treatment from coming back out of the hole. This type of system has gained popularity in the past few years as it has proven to be a fairly rapid way to inject insecticides into ash, and other widely recognized slow-asmolasses-uptake-time species of trees, including pines and spruce. These are refillable systems that can be utilized for a number of different treatment protocols, such as insecticides, nutrients and certain fungicides. Macro-infusion systems are also available in a few different versions. Dutch elm disease, which has been treated for more than three decades by macro-infusion, requires a large volume of fungicide solution applied to the tree every three years. For example, a 30-inch-diameter elm tree would require more than 36 gallons of solution to be injected (hence, macro). To accomplish this, the reservoir is often a 55-gallon drum and then an electric pump moves the solution through a series of tubing and tees into the base of the tree. Other macro-infusion setups will replace the electric pump and 55-gallon reservoir Macro injection using a large reservoir. Landscape and Irrigation 17