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Minnesota Community Living 2013-05-06 Emerald Ash Borer: Time to Take Action
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Emerald Ash Borer: Time to Take Action

By Thomas Badon, ASLA, Commercial Consulting Arborist, ISA Certified Arborist MN-4439A, Rainbow Treecare

Tom Badon

Remember back in 2009 when the Emerald Ash Borer (EAB) was all the rage? All the major networks and newspapers were covering the topic. So what has happened to EAB? You hear a story once in a while, but with this extended winter it is certainly not getting the media attention it did back then. Does that mean the beetle is gone? Have the Twin Cities beaten this pest? That certainly would be wishful thinking; unfortunately, that is not the case. The reality is that the population is silently growing and in fact, based on the history of this pest, the population is currently increasing exponentially.

So What Can You Do?

There are several theories and opinions as to the best management practices, and several cities are beginning to develop plans of attack. However, removal seems to be the preferred method. If Michigan knew in 2002 what we know today, could they have saved some of the 60 million trees that were lost? Before we answer the question of "What can you do?” let’s look first at the basic facts about EAB.

Why Are There So Many Ash Trees?

Approximately one out of every five urban trees is an ash (Fraxinus sp.) tree, primarily of the Green ash (Fraxinus pennsylvanica) variety. It is not uncommon that more than 75% of many properties’ and communities’ urban canopy consists of ash trees. The ash tree planting craze started in the ’70s and early ’80s as a hardy alternative to the American elm (Ulmus americana). When the elm trees started to die from Dutch Elm Disease, everyone wanted a hardy, tough urban tree.

What is EAB and Where Did it Come From?

The Emerald Ash Borer (Agrilus planipennis) has killed millions of ash trees since its discovery in southeastern Michigan in 2002. Native to Asia, this insect was likely introduced to the United States in wood packing material carried in on cargo ships or airplanes. Through a combination of natural spread and human activity it is now found in Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, Minnesota, Missouri, Ohio, Pennsylvania, Virginia, West Virginia, and Wisconsin, placing millions of additional ash trees at risk.

Where Is it Around Here?

Managing emerald ash borer is enough of a challenge, just trying to save the trees from getting killed by beetles. However, in our roles as managers, consultants, and stewards of the urban forest we also need to be responsible for planning for the future. Back in 2002, when EAB was first discovered, Michigan had no idea what they were dealing with. As the insect spread quickly into surrounding states, Ohio knew what it was but did not know how to stop it. As the pest continues to spread, each state and community knows more and more about the pest. Unfortunately, places like Illinois waited too long to implement a proactive plan. The fact is, EAB is here and spreading throughout the Twin Cities.

How Does this Insect Kill ash Trees?

The female Emerald Ash Borer lays its eggs on the bark of an ash tree and the larvae tunnel through the bark and begin consuming the sapwood of the tree. This feeding disrupts water flow to the canopy, dehydrating and killing that portion of the tree. Eventually, the whole tree will die. Unlike Japanese Beetles or Boxelder bugs, the Emerald Ash Borer insect is small and causes damage inside the tree, making it relatively hard to detect. Since this insect often goes undetected for the first few years, the population grows very rapidly within the original tree, placing all the surrounding trees at high risk. Researchers at The Ohio State University have studied this "Curve of Death” since the original find and have discovered that it is possible that approximately 80% of the ash population can become infested and die within a four-year time frame.

What Should I Look for?

First and most importantly, correctly identify that you are looking at an ash tree. Ash trees can most easily be identified by the shiny, dark green leaves that are compound (5-7 smaller leaves per leaf) and typically grow opposite of each other on a branch. Once you’ve identified your tree as an ash, begin to look for symptoms. Typically a tree will start dying from the top down, losing 30-50% of its canopy after two years of infestation. As the top of the tree continues to decline, epicormic shoots (new branches) begin to form near the base of the tree as the tree’s last hope to survive. If the tree is heavily infested, the bark will begin to sheer off revealing distinct "S” shaped galleries where the larvae have been feeding. The final tell-tale sign is "D” shaped exit holes about 1/8 inch wide created as the adults emerge from the tree. Due to the coarse nature of the bark, these can be difficult to spot at first glance. Typically by the time they are visible and near eye-level, the tree is already heavily infested.

Who Should I Listen to?

A Google search of Emerald Ash Borer yields more than 600,000 results. For as much quality information that is out there on EAB, there are more myths, confusions, half-truths, and misconceptions around this insect than maybe any other tree pest in history. To help combat some of this misinformation, the Coalition for Urban Ash Tree Conservation was formed. The Coalition consists of academics, researchers, and industry scientists who strive to get a consensus from industry leaders on the best management practices for treatments and/or removals. Their documents, as well as relevant information, can be found at This site is a collaborative effort of the USDA Forest Service, Michigan State University, Purdue University and Ohio State University. Additional information can always be obtained by contacting a professional and licensed tree care company; however, it is important to understand all available options before making a decision.

What Are the Options?

The first option is to do nothing and just wait and see what happens. Although this approach is certainly tempting, it will eventually lead to the removal of the tree. Based on the historical movement of this insect since it was first discovered in 2002, every community affected by EAB has experienced the exponential death curve. While the insect population begins to build, very few trees die within the first four years; however in years five through eight, as many as 80% of the ash trees can die.

Should I Cut Down My Ash Trees?

This may seem like a good idea at first. After all, shouldn’t fewer ash trees result in fewer ash borers? Although this might help your property, if you remove the insect’s food source in one spot they will simply fly further to find another. At this point, many municipal management strategies have focused on removing boulevard ash trees — which simply moves the insect to private properties or to trees in naturalized areas. Preemptively removing all ash trees can actually help quicken the spread of an established EAB population, rather than slow the spread as intended.

Can I Save My Ash Tree?

In both field trials and in actual practice, treatments have been saving trees for many years now. With almost ten years of research behind a variety of insecticides and application rates, EAB treatments are as effective and predictable as any tree health care management program in the industry. In fact, as a quarantined pest, any product labeled for EAB treatments must provide accurate data to the EPA to be considered for registration. In addition to data submitted to the EPA, numerous independent university trials have also shown treatments have a high level of success when used as directed.

What Are the Treatment Options and Which One Is Best?

Although strong marketing efforts by product manufacturers may lead you to believe one is better than another, that is simply not true. In fact, often the "one size fits all” concept of EAB management is rarely the best option for either property owners or municipalities. There are three scientifically proven effective treatments and three scientifically proven application methods that are effective. When it comes down to it, there are literally dozens of insecticides that would kill EAB on contact. That said, for the highest degree of control combined with the realities of application operations, there are three main active ingredients that are recommended by universities and the Coalition. Those three are emamectin benzoate (TREE-age), imidacloprid (Xytect, Merit, others), and dinotefuran (Safari, Transtect). There are also several ways in which these treatments can be applied. Soil applications (imidacloprid, dinotefuran), tree injections (emamectin benzoate, imidacloprid), and systemic bark spray applications (dinotefuran) are all viable application methods for EAB management. Choosing the perfect combination of active ingredient and application methods can vary by pest pressure, economics, and management objectives. Ensuring the stakeholders are aware of all the options available is important to make the most informed decision.

Are Treatments Expensive?

Expense is certainly relative to the opinion of the tree owners and stakeholders. The first step is asking the question, what is the value of my trees? Economically speaking, you can calculate this at Although it may consider storm water retention, energy costs, and environmental qualities, this calculator does not factor in any emotional attachment, privacy value, etc. Unfortunately, it also does not factor in the politics of working with neighbors or public perception of removing trees.

If treatment is right for you, it has been said that you can economically treat a tree for more than 10 years for the cost of removal and replacement. If you were to factor in the aesthetics, the environmental benefits, and the property value a mature tree provides versus a newly planted tree, saving trees is a gain. However, it is important to consider that not all trees can or should be saved. Perhaps this is an opportunity to remove and replace the trees that were planted in the wrong place, have poor structure, have been damaged by storms in the past, or are a general nuisance.

Where Do I Go from Here?

Create a plan and budget. It does not mean you have to treat or remove trees instantly, but having a plan and being ready when the time is right for your property can mean the difference between a beautiful property and an economic disaster. The plan should first begin with identifying the ash trees on your property. While identifying them, one should evaluate and rate them based on good structure, overall health, or any emotional attachment. Simply ask yourself, do I or the community want this tree? From there, you should decide if you are planning to treat the tree or not. If not, begin to save money for removals and replacements. If you decide to remove and replace trees, remember to replace with a diversity of species to avoid history repeating itself.

Considering the relatively short history of EAB, this insect will cost you — either now or later. Now is the best time to take action and manage EAB before it affects you and your property.

Published by Community Associations Institute — Minnesota Chapter, copyright 2013. All articles and paid advertising represent the opinions of authors and advertisers and not necessarily the opinion of either Minnesota Community Living or CAI–Minnesota Chapter. The information contained within should not be construed as a recommendation for any course of action regarding financial, legal, accounting, or other professional services by the CAI–Minnesota Chapter, or by Minnesota Community Living, or its authors. Articles, letters to the editor, and advertising may be sent to Chapter Staff Editor Joe Flannigan at, or at CAI–Minnesota Chapter, 1000 Westgate Dr., Suite 252, St. Paul, MN 55114.

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