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Tree pests are a constant battle. To discuss tree pest concerns for 2011 as well as identification and management, Arbor Age recently interviewed Rob Gorden, national sales director for Arborjet.

Tree Pest Identification and Management

Tree pests are a constant battle. To discuss tree pest concerns for 2011 as well as identification and management, Arbor Age recently interviewed Rob Gorden, national sales director for Arborjet. Gorden provides support to municipalities evaluating treatment options for invasive pests across the country, and he is a frequent speaker to city arborists, public works directors, local arborists, extension agents, applicators, and master gardeners.


Arbor Age: Emerald Ash Borer (EAB) continues to spread to new areas, but, at the same time, management options, application methods and overall understanding of EAB continue to improve. What are some of the key messages or updates that you would like to convey to arborists — both commercial and municipal — regarding EAB?


Gorden: Perhaps the most significant point warranting our increased emphasis is that the cumulative evidence on treatment effectiveness and the resulting ability to preserve our urban ash forest has become undeniable. Recently, a loose coalition of university and industry leaders published a statement endorsing the preservation of urban forest ash trees as a part of any EAB plan. People have previously discussed, pondered and argued around four main issues, which today are well resolved:

1. Treatment effectiveness – Studies using various treatment methods and chemistries have demonstrated control as low as 60 percent of EAB larvae, while others are so effective, that they often exceed 90 percent control. This has resulted in simplistic but erroneous statements such as, “Treatment results for EAB are inconsistent.” Taken literally, one can see how this factually inaccurate generalization could be made. In reality, there are a select few, highly effective treatments that will protect uninfested trees, and even save trees under attack.

2. Treatment longevity – While it has been argued that annual residential treatments are acceptable to the public, the most effective treatment actually provides two years of protection against EAB by label, and research has suggested even longer protection may be possible. This is particularly important for cities considering treatment, as less frequent treatment means that the cost of treatment is lowered even further, and provides a wider interval when cities consider re-treatment. The logistics of managing city tree EAB plans is greatly simplified with reduced treatment frequency.

3. Cost of treatment – The protection afforded trees against EAB following a single two-year trunk injection has shown that treatment costs will not equal city removal and replacement costs for over 30 years. Most accurate estimates of average removal and replacement costs for city trees, range from $750 – $1,000 per tree. Actual treatment costs for cities have been accurately documented to include labor. This practical real-life data has demonstrated that a tree can be protected for two years for as little as $3.05 per inch DBH. For an average 17-inch DBH tree, treatment costs would be about $52 for two years of protection. Cities often re-treat in the year following loss of this two-year protection.

4. Environmental considerations – Today’s newest tree injection technology seals the medicament in the trunk, reducing dramatically the potential impact to soil, water or air. On the other hand, the impact of tree removal is substantial and well documented, from stormwater runoff to increased heating and cooling costs. Many of the impacts associated with tree removal, are spelled out in great detail through programs such as the USFS I-Tree, and by exploring the website www.treebenefits.com/calculator. From a neighborhood perspective, tree removal alters the character of a neighborhood, and places greater stress in the community — lowering property values and increasing the cost of maintaining a home. We have already witnessed too much preemptive tree removal.

To summarize; EAB can be managed, and we don’t need to lose our urban ash trees in the process. With the newest trunk injection technology it is logistically effective, environmentally responsible and fiscally sound. These treatments are highly effective and can even control EAB in infested trees — but preventative treatments are always the best approach. A city can treat its trees for decades, if necessary, before the cost of treatment will equal the cost of removal and replacement.


AA: What are some other tree diseases and insect pests that pose the biggest challenges for arborists right now and in the near future?


Gorden: There are over 400 invasive pests in the U.S. currently, with new ones arriving monthly as a result of our international commerce and travel. What dictates the “biggest threat” can often depend on where you reside in the country, as we often don’t recognize the impact until a pest becomes established in an area where our native trees lack defensive capabilities. Some of the more destructive pests we are seeing include Spiraling White Fly and Chili Thrips in Florida, Gold Spotted Oak Borer in California, and the Asian Longhorned Beetle in the northeast. More regularly now, the changing climate conditions exacerbate existing native pest pressures, making them extremely destructive. These include the Mountain Pine Beetle in the west and the Southern Pine Beetle in the south — both made deadly and far reaching by protracted droughts. A new pest, spreading rapidly and attacking fruit trees and vegetables in the east, the Brown Marmolated Stink Bug, originated in Asia. It was found first in Pennsylvania in the 1990s.


AA: What other advice do you have for those professionals who want to become experts on pest identification and management?


Gorden: Each year, industry leaders, local extension agents, ISA chapters and the TCIA sponsor countless sessions to increase arborist knowledge. Often however, as is the case with invasive pests, the problems and solutions are changing faster than the needed knowledge spreads, so visiting respected websites, participating in forums, and seeking current research results are some of the best ways to stay current. Most of us know that the best education comes from practicing and working with others who have experience. The most important characteristics necessary for success are to remain curious, ask questions, and to dig for answers when you don’t get the answers you want. Many universities offer short courses geared to landscape professionals over the cold months, but ultimately the responsibility to learn is yours. Your customers demand and deserve it, and the industry needs it. Professionalism in arboriculture requires continuous educational advancement.


AA: What recommendations can you offer in terms of application methods and timing with regard to the related effectiveness controlling some of the major tree diseases and insect pests?


Gorden: The nature of how and when we control destructive pests of trees is changing, and will continue to change rapidly. Tried-and-true methods just a few years old are abandoned as newer chemistries enter the market with longer residuals and lower doses.

This is not just a matter of efficacy, as products with longer residuals and pests that have never attacked our trees previously require that we employ new strategies. For instance, the Asian Longhorn Beetle has required a two-pronged approach — the destruction of existing, infested trees, and a three-year treatment of host trees in the USDA APHIS designated controlled areas.

This means that we are using control products in tens of thousands of trees, but must remain sensitive to the ecological impact of both tree loss, and insect control use.

Another factor which has changed the way we implement control methods, is application timing. In the past, treatment timing was often a weak link in many arboricultural programs. Rate of leaf-out in the spring, rain, wind, cold, or rapid warm-up often affected our ability to provide effective control methods. With the newer injection technologies and longer residual products, some treatments can now be made well in advance of the actual risk of damage, thus preventing it, and allowing the arborist to manage both time and priorities to deliver effective protection of plants, satisfy clients, and increase activities fostering the growth of their businesses, like responding to requests for estimates as they come in.


AA: What other factors, if any, should professional arborists be aware of as they prepare to manage tree pests this year?


Gorden: I am a firm advocate for researching the research, asking questions, and demanding proof when new products, treatment methods, or strategies are developed or suggested. Marketing is important to all of us, but does not replace careful analysis of the research, and examination of their conclusions. Is it proven by university research, or only on a company website? Will it improve my results, or am I just substituting one product for another? Ultimately, our clients enlist our aid because they lack the skill or education to protect their trees. Our professional reputations are at stake as an industry every time we walk on a property, or make a diagnosis. Ultimately whether in the public or private sector, we must truly be a tree doctor.

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