Vigilance, Prevention Key Amid Spread of EAB

Emerald Ash Borer has continued to spread to more areas of the U.S., and those "on the fringe" of infestation should consider preventive measures early on.

Exit hole of Emerald Ash Borer.
Exit hole of Emerald Ash Borer.
Photo courtesy of Kenneth R. Law, USDA APHIS PPQ,, University of Georgia.

Emerald Ash Borer (EAB) has continued to spread to new areas of the United States. Originating in Michigan and then permeating throughout the northeastern quadrant of the country over the past decade, EAB has most recently been identified in places like Wisconsin, Minnesota, Iowa, Kansas, and even down south in Georgia. In September of this year, EAB was found in Boulder, CO.

Scott Roberts, a technical manager for TruGreen, says the spread of EAB cannot be stopped, per se. But the damaging effects of EAB can be prevented, to a degree.

"We've learned a lot about what areas in Michigan and elsewhere have suffered through over the past decade," Roberts relates. "Seeing how they tried to manage the problem, along with all of the research that has been done since, we had a pretty clear idea of how to manage the pest by the time it got to Chicago. Now, as it sweeps further west and south, we know what can and can't be done to control it—if the tree owner chooses to do something." Roberts is based in the Chicago area and covers the upper Midwest.

Prevention the Best Medicine

Prevention is the right way to go, Roberts points out, but tree owners need to make the commitment early on. "Conventional wisdom says that if you're within 15 miles of a known infestation, and you want to save your tree(s), you should begin treatment," Roberts explains. You should contact your university extension or visit to keep an eye on where EAB is showing up. Roberts says he is keenly watching areas of Wisconsin and the Twin Cities of Minnesota right now.

Tree care and/or landscape contractors can play a role in building awareness and providing the treatments for customers located in EAB fringe areas. That's exactly what TruGreen is making a concerted effort to do. "We're continually leaving information with our customers that have ash trees," Roberts says. "We're pointing out that EAB is in their area, along with what can be done if the customer is interested in saving their tree(s). We also point out what we can do to help them."

Product technologies have come a long way. "There are a couple of different active ingredients on the market that can help control EAB," Roberts says. "We now use a trunk injection method (commercially known as TREE-äge from a company called Arborjet). We inject the trunk of the tree, which then provides protection for a full two-year period."

Identification Tips

A tree that has been infested by EAB will show general crown thinning. "This insect will usually attack and start at the top of the tree and work its way down," Roberts explains. "So the foliage will start to thin out, and some branches won't look as full as they used to. That will progress rapidly over a couple-year period until the tree eventually dies in three to five years." That's why it's so important for homeowners and their professional contractors to catch it early.

At the same time, Roberts adds, it's very difficult to stand next to an ash tree, look up and spot the insects. "The Emerald Ash Borer is small to begin with, and first attacks high up in the air. So you really have to just look for symptoms on the tree itself."

In addition to crown thinning, symptoms include:

  • Ash tree begins to sprout growth from the roots and trunk
  • Those leaves are larger than normal
  • Fissures appear on the bark
  • Larvae feeding galleries weave back and forth
  • D-shaped holes (where adults exit the tree)
  • Increased woodpecker damage

It shouldn't be overlooked that one challenge in the field is that many homeowners and property managers aren't even sure how to identify an ash tree in the first place. While it's hard to vividly describe with words, here are a few things to look for:

  • Branches and buds are directly across from each other as opposed to being staggered
  • When present, seeds are dry, oar-shaped samaras which usually occur in clusters
  • Bark has a distinct pattern of diamond-shaped ridges
  • Leaves are compound with 5-11 leaflets, are moderately toothed, and may be stalked or sessile (attached directly to base/main stem)

But as the old saying goes, a picture is worth a thousand words. Download this document from TruGreen: Recognizing An Ash Tree. Then the next steps are to continue to remain vigilant, and implement a plan of prevention when/if EAB closes in on an area. Professional landscape and tree care companies like TruGreen can help.

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