Arboriculture in the Twenty-First Century: Treating Iron Chlorosis
Published November 29, 2006 By KEVIN BASSETT and RUSSELL PETERS
The science of Arboriculture is advancing rapidly as is most every area of science. Our understanding of trees has increased dramatically during the relatively short period (26 years at the time this article was written in 2006) of our company’s existence. New treatments for improving the health, beauty and safety of trees are coming forward at an ever-increasing pace. As part of our commitment to serving our clients, we are continually learning of and evaluating these new treatments and technologies for use in a practical manner for the benefit of our clients and their trees.
Dr. Alex Shigo recently died and his career of over 50 years was highlighted by increasing the knowledge of tree anatomy, physiology and how trees deal with wounding. He studied trees with a chainsaw and a microscope and was a great educator of our industry’s young and coming arborists, including us. Yet, he always acknowledged that he learned more about trees from arborists than from any other source. Because of his work, most professional arborists now know that painting tree wounds has no positive effect on a trees ability to respond to wounds and the decay process. We now know that pruning limbs and branches at the branch collar is the best and least damaging way to remove a branch or limb. We now know and understand that tree roots live and grow with associated micro-organisms in a symbiotic manner and that these organisms are vital to a tree's health. We apply this knowledge in an artful manner daily for the benefit of our clients and their trees.
As young arborists, we became aware of a new idea in Arboriculture that utilized injection of materials directly into the trunk or roots of a tree. The first use of this technology was in fighting vascular diseases of trees such as Oak Wilt and Dutch Elm disease. Although this technology is far from a cure all for these diseases, it has become an effective tool for managing these diseases and their spread through the tree community.
Many different systems for injecting these materials have evolved and become commercially available over the last thirty years. Fungicides, insecticides and micro-nutrients have been introduced with varying degrees of success. Some of these materials have been used to attempt the correction of basic site related problems such iron deficiency symptoms or Iron Chlorosis. The problem has always been that certain trees are not able to utilize iron that is tied up in the soil due to high soil pH. This issue is true in the Dallas area where high soil pH leads to a variety of problems for species such as Sweet Gum, Silver Maple, Magnolia and certain species or hybrids of Red Oak. You will notice these trees by their characteristic yellow leaf color.
Recent developments include an injectable material know as ‘Verdur®’. This treatment has shown a great ability to supply the affected trees with iron and increase the trees ability to synthesize chlorophyll. The result is green, healthy leaves and a healthier tree better suited to deal with all of the stresses that go with urban life for a tree. Past injectable treatments for this problem have failed because the material was used up quickly. As a result, the tree would have to be injected on an annual basis to maintain the result. This resulted in a lot of small wounds at the base of the tree and these wounds became entrance courts for decay organisms. The cure was in effect as bad or worst than the disease. With this in mind, our efforts to help address this specific problem have been to provide the nutrients needed through the soil via our deep root invigoration programs. We add sulfur to help lower the soil pH and a chelated form of iron that is readily available to the tree. This treatment helps many of the trees affected by this problem, but this approach requires frequent repeated treatments to achieve and maintain a good result. Additionally, problems arise when a portion of the root area is not accessible for treatment application. In these cases, part of the tree becomes green and another portion has no improvement. We are hopeful that ‘Verdur®’ will become another effective tool that can be used in conjunction with our normal treatment to help with this problem.
Since yellow leaves on trees can be caused by many different ailments or pathogens, it is important that any treatment be recommended by your arborist. As always, Arboricultural Services treatments usually involve a trade off. Yes, the injection of ‘Verdur®’ can help with the yellow leaves on your trees, but there is still the wounding aspect. The good thing about this material over other materials, is that this material will remain in the tree supplying the needed nutrients for up to three years. This makes the wounding of the tree more tolerable. This approach to treatment of iron deficiency is the one that you are more likely to see recommended by your arborist.
Despite the gains in science, it remains true that the best trees for our area are native trees and those species that are adaptable and have proven their ability to thrive in the rigorous conditions present in our north central Texas area. Yet, we now have another tool that when applied wisely can be helpful.
As a client of Arborilogical Services, Inc., you can depend on our vigilant efforts to stay on top of the everchanging advancements in the science of Arboriculture, and the judgment of when and where these new treatments and technologies are prudent. But, despite all of these advancements, Arboriculture remains an art as well as a science.