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EAB Continues To Spread

The invasive and potentially devasting Emerald Ash Borer continues to spread throughout the Metro Area. In December, an EAB infested tree was discovered in Eagan. This means that the pest continues it's spread from the original epicenter in discovered in St. Paul in 2009. Although the spread has been slower than originally expected, the insect is, in fact, spreading. If you are new to the insect, here is a little information to help answer any questions you might have. We would be happy to meet with you and perform a site analysis of your property to determine if you have ash trees and what your options are.

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.

Where is it around here? The fact is EAB has been here since before 2009 and is spreading throughout the Twin Cities. The known infestations sites include Minneapolis, St. Paul, Roseville, Shoreview, and Eagan and the pest has shown up at landmarks such as Ft. Snelling Golf Course and Lakewood Cemetery. For the latest known infestation locations, please visit the Minnesota Department of Agriculture’s website at

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 begins 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. 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 trees 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 too? A Google search of Emerald Ash Borer yields over 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. Their documents, as well as relevant information, can be found at 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.

So what are the options? The first option is to do nothing and just wait and see what happens. Although this approach is certainly tempting, this approach 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.

So 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.

Are treatments expensive? This 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 this may consider storm water retention, energy costs, and environmental qualities, this calculator does not factor in any emotional attachment, politics, privacy value, etc. If treatment is right for you, it can be said that you can economically treat a tree for over 10 years for the cost of removal and replacement. 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, however 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 want this tree? From there, you should decide if you are planning on treating 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 diverse variety of species to avoid history repeating itself.



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