Emerald Ash Borer: The Truth About A Hidden Threat to Washington’s Forests

Affiliate Disclosure: As an Amazon Associate, the Master Gardener Foundation of Washington State earns from qualifying purchases. When you buy through our links, you’re helping The Evergreen Thumb Podcast grow—just like good fertilizer! Product recommendations are our own and do not represent the views of MGFWS or Washington State University. Thanks for supporting us!

In this episode, Patrick Schults of WSU Extension discusses the threat of the Emerald Ash Borer, an invasive insect that poses a significant risk to Washington’s forests and urban trees. Learn about how it spreads, signs of infestation, and what communities can do to prepare and respond.

• Forestry.wsu.edu
• Extension.wsu.edu/product/emerald-ash-borer-and-its-implications-for-washington-state/
• Extension.wsu.edu/product/managing-emerald-ash-borer-in-washington-state/
• Washington Invasive Species Council
• Preparing for Emerald Ash Borer in Washington State
• Emerald Ash Borer Resources
• Emeraldashborer.info/homeowners
• Report a Sighting – Invasive Species Council Report an invasive species sighting
   

Erin Hoover (00:00)
Welcome to The Evergreen Thumb, episode 69. My guest today is Patrick Schultz, WSU Forester. And he’s here today to talk to us about Emerald Ash Borers and the risk that they pose to Washington forests. Patrick, thanks for joining me today. Welcome.

Patrick (00:17)
Thank you for having me. Excited to talk EAB today.

Guest Introduction

Erin Hoover (00:22)
Can you take a moment to introduce yourself to listeners and talk about your role at WSU?

Patrick (00:28)
Yeah, absolutely. So I’m Patrick Schults. I’m an Extension Forester with WSU Extension. So, part of the Extension Forestry Team. There are six or seven of us now across the state. I’m in Olympia in a kind of a specialist, more project-based position these days, but was formerly running the program for Southwest Washington.

Erin Hoover (00:56)
All right, that’s my home region too. I’m just south of you.

So, would it be fair to say that part of your role is helping forest landowners identify possible threats to their forest?

Patrick (01:09)
Yeah, absolutely. And for those that don’t know what Extension Forestry does, we certainly do a smattering of things, but at our core, we are providing support to forest owners to better steward their forests. That means, you know, educational trainings, field research, sometimes developing resources, digital resources, publications, things like that.

And certainly, we like to say the one objective that everyone has for their forest is to keep it healthy. Everything else can be super diverse. Some people want timber, some people want wildlife, but everyone wants a healthy forest. So, we do place a lot of emphasis on identifying forest health risks.

Understanding the Emerald Ash Borer

Erin Hoover (01:52)
And today you’re here to talk to us about one of those health risks, the Emerald Ash Borer. So, can you tell us a little bit about it and how it spreads, or actually what it is?

Patrick (02:03)
Yeah, of course. Yeah. Emerald Ash Borer is an invasive insect, an invasive forest pest. So it is from Asia, usually, like people say, China, Japan, that kind of area. And there it is, a secondary pest that evolved with their forests. It doesn’t cause really big problems.

That’s the nature of invasive species, invasive diseases, and pests, is that when they get transplanted out of that space and brought to new ecosystems, a small percentage of those that do get transplanted turn into invasive pests and diseases, and they cause a lot of destruction. Emerald Ash Borer is considered the most destructive invasive forest insect in the history of the US.

So it is a green, metallic, wood-boring beetle in the Buprestid family. If you’re ever bored and want to just look up really beautiful insects, look at the Buprestid family, because they’re all just glittery, shiny little beetles. For all the problems it causes, Emerald Ash Borer is actually really pretty to look at, because it’s emerald, just like it describes.

So in 2001, I believe, Emerald Ash Borer was discovered in Michigan, not too far from where I grew up. I grew up outside of Flint, and it was found in Detroit.

And it was believed to have come on some shipping materials, like a lot of invasive insects and diseases. And since then, it has spread to over 30 states, multiple provinces in Canada as well, including now, Oregon and British Columbia. So we have not found it in Washington yet, but we’ll get to it. But I believe it’s here. We just haven’t seen it yet.

And the real crux of what it does is it bores into Ash trees, it feeds on the living tissue of it, the phloem, and in the process kills those trees. It’s very effective, and often in the 97% to 100% mortality rate, which is, I mean, we’re talking about whole stands of Ash being wiped out in forests where Ash is a little more present. So it’s a very devastating invasive insect.

The Importance of Ash Trees in Washington

Erin Hoover (04:19)
So I know Ash trees aren’t usually the first tree people think of in Washington. So, why should we be concerned about Emerald Ash Borer in Washington?

Patrick (04:30)
It’s a really good question. And I think a lot of people think exactly that. For that reason, when they see the news reports, they kind of maybe shrug it off a little bit. And I’m not going to be a doomsday person on this podcast at all. But I think you should be concerned because Ash trees, although not nearly as ubiquitous as they are in Eastern forests, really pull their weight in Washington forests.

We’ll talk about Ash trees in two places. There’s the urban community environment, and then there’s the forest natural ecosystem environment. And the latter, our native Oregon Ash, we only have one native Ash tree, Fraxinus latifolia. It serves a very important niche in the forest, and it’s a wetland species.

It’s one of the few trees that can grow with its feet super wet most of the year. It likes water even more than Willow or Cottonwood. And for that reason, you get these sites that are maybe a little bit less common but are completely dominated by Ash often.

So, where we will see Emerald Ash Borer damage, we’ll see it really intensely, I think. Many forest owners may not have a single Ash tree on their property, but those that do often have a lot of them. So they’re going to be disproportionately affected. And those wetlands, those ecosystems will be disproportionately affected. And I’m sure we’ll get into that a little bit more, but there’s just not a lot of good substitutes for those trees.

So, that’s really important. On the other side, the community urban side, Ash trees are really common landscape tree in urban settings. And we know that trees similarly pull their weight in urban settings. They do provide a lot of benefits. Even just a few trees can provide a lot of benefits in terms of providing shade, reducing that urban heat bubble, serving as stormwater infrastructure, and reducing flooding.

We have all these impervious surfaces in urban areas, and trees are really important. Green infrastructure to help mitigate some of that stormwater that happens during flood incidents.

So yeah, so these trees are really important. Some cities have as high as 30% Ash in their urban canopy, so losing 30% of your urban canopy is a really big deal, and we also know that it can disproportionately affect poorer communities as well. And then we’ll get into like tree removal and the cost of that, and that certainly affects poorer communities as well. Like it really causes quite a few complications, even if you don’t think you see an Ash tree every day. It’s going to be significant.

Identifying Early Signs of Infestation

Erin Hoover (07:24)
So, what are some early signs of infestation, and how can gardeners or forest owners recognize those?

Patrick (07:33)
Yeah, it’s really tricky. So one of the things that makes Emerald Ash Borer kind of unique is it’s one of the few pests, tree pests, that actually starts at the top of the tree and works its way down. So the adult Emerald Ash Borer likes to feed on the leaves of the tree.

But we’re not really worried about defoliation. That’s not really going to be the significant cause of mortality. What happens is that after they feed on those leaves, they get nice and full, and then they go and they bore into the stems and trunk of the tree, and then they lay eggs just under the bark in that phloem that’s responsible for sugar transport in the tree. And so it’s nice and sweet, full of sugars. That’s what they’re feeding on. And so they do that, starting at the top of the tree and then kind of work their way down.

And by the time that you start to see any symptoms, which would be things like tree canopy dieback, loss of foliage, essentially, that’s one of the first signs that you’ll see. The tree is pretty much done for. Ash borers have already worked their way down to the stem as well.

So, tree canopy dieback, you’ll also see in those early stages what’s called Epicormic branching or Epicormic shoots, and that’s branches that are starting to form from the bottom of the tree or the trunk of the tree as opposed to at the tips of the branches.

Because, that’s where trees should be growing and putting on vertical growth or horizontal growth is out of the tips of their branches just trying to spread their canopy and grow a little bit taller but when they’re under significant stress or they know that you know some of their canopy is dying it sends the stress response that forces them to start sending shoots out of the base of their trunk and other parts of the trunk as well. And that’s really not common unless the tree is under stress. It can happen for other reasons, though, as can canopy dieback.

It’s important to note that there are other things that can cause that. For instance, if you hit your tree with a lawnmower, that might stress it out enough to start Epicormic branching. That does not necessarily mean that you have Emerald Ash Borer or any other pest as well. So yeah, those are the early signs.

What to Do When You Have an Infestation

Erin Hoover (09:43)
Okay. So what can homeowners or forest owners do if they suspect they have Emerald Ash Borer?

Patrick (09:55)
Yeah, if they suspect that they have Emerald Ash Borer, I would say start with a couple of good publications that we have through WSU Extension that talk about how to properly identify that damage or that insect. If you’re just dealing with an insect, a green insect, there are a lot of lookalikes as well. More often than not, people aren’t just running into green bugs; they’re looking at trees and seeing that they’re not looking so healthy.

The first question you have to ask yourself is, is it actually an Ash tree? And not everyone knows how to identify their trees, so there’s no shame in getting that wrong. One of the most common things I see is people sending pictures of things like Walnut trees, because they also have those compound leaves similar to Ash trees. Or Mountain Ash, which is not actually in the Fraxinus genus. It’s just an Ash in the common name only.

So you really need to know whether or not you’re dealing with an Ash tree in the Fraxinus species, and there are a lot of apps that can help with that, like Seek, it’s a good one or guides online as well.

Then the next thing I would say is to go and take a look at that tree look a little closer one of the pivotal signs for Emerald Ash Borer is a D-shaped exit hole on the bark of the tree, and so that means it’s about a half circle with a flat side. So just like the shape D. And that’s a very unique shape. And it’s unique to the shape of the Emerald Ash Borer.

As those babies, the eggs, hatch and they turn into adults underneath the surface of the tree, and they drill their way out, that’s the shape that they leave. And so that’s a really, really strong indicator that you have Emerald Ash Borer. Now, if you don’t see that on the trunk of the tree, that doesn’t necessarily mean it’s not there.

It could be something else, like drought stress, that’s causing that canopy dieback as well. Now if you do happen to see a green bug, take a picture, take a sample, put it in a bottle, and put it in the freezer. It’s a great way. And then take some pictures and send it to the WSDA invasive species council, which, if you just Google that, they have a hotline and you can send images or send pictures just to get a confirmation.

But if you’re not sure and you just like really want some support, you can always reach out to, I personally think Master Gardeners are going to be a great resource for this, dealing with this at the community level. I really hope to be a resource for Master Gardeners to get trained in this, but folks can also come to me or any of the other Extension forestry team if they just aren’t sure and they want to double-check. But I would say, those that key one there is making sure that you’re at least dealing with an Ash tree first.

Misconceptions and Mistakes in Identification

Erin Hoover (12:43)
It does seem like a logical place to start because I can see how Ash trees could easily be misidentified.

Patrick (12:46)
Yes.

Right.

Erin Hoover (12:50)
Are there any misconceptions or mistakes that people might make that would cause them to maybe overlook the problem or misidentify?

Patrick (13:02)
Yeah, well, we talked about misidentifying trees. That is honestly so far, that’s been like 90% of it, frankly. But no shade, pun intended, to people for not knowing their trees. Not everyone stares at them all day like I do. But I think one of the things, big things right now is confusing drought damage with insect damage. It’s really hard to tell them apart. I can’t tell them apart just by looking at a tree.

That canopy dieback is really common in a lot of tree species right now because we’re having hotter, drier summers. In fact, if you drive along I-5 between probably between you and I, between Chehalis and Olympia, kind of just north of the highway 12 exit to Oakville and Rochester, there are a lot of Ash trees that have canopy decline and I didn’t stop and take a look, but someone else with expertise has, and just found that it’s drought damage.

But it would be really hard to tell that. So I just say better safe than sorry. What I would say, though, is by the time that a tree is really starting to show those signs in the canopy, like serious canopy decline, you should be seeing those D-shaped exit holes on the trunk. So if you’re not seeing those, that should probably put your mind at least a little bit at ease.

Current Prevalence and Lessons Learned

Erin Hoover (14:23)
So, how prevalent is it in Oregon or in other neighboring areas right now?

Patrick (14:31)
So in Oregon, I believe it’s spread to three counties in and around the Portland area. With Emerald Ash Borer, we have to assume that it has spread farther than you think. What they generally say is, when it’s within 30 to 50 miles of you, a reported sighting, you should start treating it like it’s in your neighborhood, because it takes so long to see those symptoms, though. But so far, I think it’s only been identified in three counties in Oregon, and maybe, I think one area outside Vancouver in British Columbia. I’m less clear on that one.

But the fact that we’re sandwiched on both sides by identification means that it is very much most likely here. I think everybody kind of in the forestry community is in consensus that it’s in Washington. We just haven’t identified it yet. You know, it takes time.

Erin Hoover (15:29)
So the most likely then is probably like Pacific County and Clark right along the Columbia.

Patrick (15:35)

Yeah, I would think Clark County would probably be the first place we’re going to see it, most likely. Yeah, Clark Cowlitz, Wahkiakum…

Community Management and Treatment Options

Erin Hoover (15:48)
Okay. So what kind of lessons have been learned from Oregon and other states that have been dealing with this infestation?

Patrick (15:57)
Yeah, I mean, it’s not great news. Because no one’s been able to contain it. You know, it took a long time to get to the Pacific Northwest because we have mountains and not a whole ton of east-west traffic in terms of plant materials. But it is finally here, and it will continue to spread through the Pacific Northwest. That’s what we’ve learned in other states: the goal is not to stop the spread. Well, first, the goal is not eradicating.

We cannot, like most invasives, at this point, we can’t eradicate it. It’s very, very unlikely, if not impossible, to get rid of it completely. With Emerald Ash Borer, it’s unique that we don’t feel that we can. I shouldn’t say it’s unique; there are other pests like this, but we don’t feel we can stop the spread either.

The goal is to slow the spread, limit the spread, and give ourselves time to implement different management practices that can build more resilient forests to the Emerald Ash Borer. That doesn’t mean trees that are resilient. It means forests that are resilient as a whole. So that’s important clarification. And one of the key things that anyone can do, listening to this, whether they own forest land or not, is to limit the movement of firewood.

The main way that Emerald Ash Borer spread throughout the Midwest, East into the South, and now out West is by movement of firewood, strongly suspected. One of the reasons it’s suspected is that camp sites were often the hot spots. The beetle itself only travels about two miles a year. So, and it’s only been around for about 25 years. In theory, it shouldn’t have spread more than, you know, 50 or, be conservative, call it a hundred miles, but it’s spread 1000 miles, and it’s only because of human activity.

So, limiting the movement of firewood in this case, obviously, Ash firewood, but I generally recommend limiting moving firewood at all because it’s just good behavior. We don’t know what invasive species is going to come next that could cause significant damage, and if we make it sort of a culturally learned lesson that it’s not good to move firewood long distances, untreated firewood to be clear, then we can hopefully prevent future invasive species or at least slow them down.

Erin Hoover (18:27)
I’ve noticed in the last few years, in places like the National Forests and a lot of the public campgrounds, they specifically ask you not to bring in your own firewood, but they don’t really explain why that’s such an important thing. And people are just like, I’ll bring my own firewood. So that kind of adds some context to why it is really is important not to bring your own firewood into the National Forests or into those public campgrounds.

Patrick (18:40)
Yeah.

Right?

Big time. Yeah. And I know no one likes paying $7 for some softwoods that are going to burn up really quickly. I totally get that. I like to think of it as an excuse to support your local forest owner’s roadside stand. So, you know, I get it. I get the impulse for sure. I always tell people, at least not move it outside of your county. That would be a major step for us.

Erin Hoover (19:21)
Definitely. So do you have any examples or stories of communities that have kind of slowed the spread or managed to kind of contain it?

Patrick (19:33)
You know, not really. So when I was in Michigan, finishing up school, I did work for a period in Grand Rapids, Michigan, for an urban parks nonprofit. And I had the opportunity to do some community engagement and then like shadow some arborists that were working on contracts with the city to treat Ash trees.

They had actually decided and penciled out that it made more sense to treat these Ash trees with an injected insecticide, what we call a systemic insecticide, than to wait for them to die or remove them in advance because those trees were so valuable in terms of those things we talked about earlier, like shade and green infrastructure, which I thought was really cool.

I mean, there are literally tens of thousands of Ash trees. And I don’t know that they were treating all of them, but they were certainly prioritizing certain areas, and they were treating thousands of them for sure. So, now, we haven’t discussed it, bringing that up kind of out of the blue, but for some, just a little bit of background in urban areas, treatment with insecticides is an option. It’s a very viable option. It’s highly effective.

And I can’t talk about which insecticides because I’m not licensed in insecticides, but there are insecticide options that are, you know, extremely effective. And they last, you know, two to three years. But the issue with them is that you have to keep coming back and treating them every two to three years, or eventually they will come back because the Emerald Ash Borer is here to stay.

So every person who has an Ash tree is going to have to make that decision at some point: Is this one worth treating? Or should I let it go? Should I plant another tree right now in its place so that something can kind of get started, get a head start? Those kinds of questions will be really important. And in Grand Rapids, I think they did a good job of that, as good as any, really; they were only about an hour, hour and a half from Detroit, where that Emerald Ash Borer got started. So I feel like that was a pretty good success.

I think Oregon’s doing great. Honestly, I’ve been very impressed with their response. You know, they are quarantining certain plant materials in those counties, obviously, Ash, from coming in or going out, and I think that’s going to go a long way again, not to stop the spread, but slow it.  I feel like if they had done nothing, we would be worse off for it right now. So I really respect their response as well.

Erin Hoover (22:23)
So do you see restricting the import of Ash trees from neighboring areas as a way to maybe slow it down in Washington?

Patrick (22:33)
Yeah, yeah, absolutely. It certainly gets to a point, and I think you’ll see this in most Eastern states at this point, don’t even bother with quarantine, because Emerald Ash Borer is pretty much ubiquitous at that point. But in those early stages, where it’s getting established, yeah, restricting the movement of Ash firewood, for example, or Ash nursery stock is certainly going to help slow the spread.

But it only takes one person to go camping with some Ash firewood to totally blow that open. To be fair.

Resources and Community Involvement

Erin Hoover (23:06)
Right. So what kind of resources are there? I’ll post links to the two publications that you mentioned that WSU produced. But are there other resources for learning more about Emerald Ash Borer?

Patrick (23:23)
I don’t have a ton of resources, like specific resources in mind necessarily. I would say, think about joining your local Master Gardener program. They, you know, obviously do a lot more than just Emerald Ash Borer. In fact, I mean, I most probably wouldn’t even say they do anything with Emerald Ash Borer, but I think they’re in a position to really support this, and they do a lot of other really cool stuff. So if you’re into gardening at all, and this topic interests you, I would just encourage you to look into your local Master Gardener program.

Other resources, OSU Extension has been developing a handful of resources. If you just kind of Google the Emerald Ash Borer or Oregon State, there’s some really cool stuff, including like maps to kind of show where and how it’s spreading. You mentioned the two resources that we developed from WSU Extension, and then of course, this is new for us. It’s only been a few years, but places like Michigan, Ohio, New York, all those states, they’ve been dealing with this for a couple of decades now.

And there’s a lot of good information, including extension publications, out there. I would shout out to my alma mater, Michigan State University. They have some great universe or great resources. I believe there’s a website that’s just called emeraldashborer.info that houses a lot of that stuff. And there is a really good publication on there on insecticide options for Emerald Ash Borer trees, like, in your yard.

Future Outlook for Ash Trees in Washington

Erin Hoover (24:58)
Okay. I will track down some of the links to share those so people can find those on our website for this episode.

So, what is your big picture outlook for Ash trees and forests in general in Washington, because of Emerald Ash Borer?

Patrick (25:16)
I appreciate this question because everything up to this point is super doom and gloom. We need to be prepared for it because we know that Emerald Ash Borer has a mortality rate of somewhere between 98 and 99% for Oregon Ash, our native Ash. At the same time, we are not saying goodbye to Ash trees.

I feel like it’s a story similar to the American chestnut, if people are familiar. In the 1800s, a blight, a fungal pathogen, was brought over and completely wiped-out chestnuts from Eastern forests, which they used to be a really important component of. And it’s been a hundred years, more than a hundred years of research, and chestnuts will probably never be the same as they were before, but they have developed a number of different strategies, including genetic resistance to that pathogen, and I think we could do the same with Emerald Ash Borer, but it will take time and it’ll take active management.

So I think that’s kind of the silver lining here, is we’re not, you know, I don’t think it’s not going to cause Ash extinction. But it will be a long time before we reach an equilibrium point with it, and essentially, Emerald Ash Borer becomes what we call naturalized.

Yeah, who knows when that will happen?

Honestly, they’re still asking that question in the eastern states, and we’re just starting here. In the meantime, it’s just really important, especially for forest owners, that you start to think about this if you have a lot of Ash. Again, we’re not trying to stop the spread, but there are things we can do to slow the spread. There are things we can do to help mitigate some of the negative impacts on those Ash-dominant forests on the wetlands.

I think it’s a good opportunity for forest stewardship if we can spin it that way.

Final Thoughts

Erin Hoover (27:11)
Definitely. So, do you have any final thoughts about Emerald Ash Borer and its future in Washington?

Patrick (27:19)
I think we covered just about all of it. Just don’t move firewood if you can. And stay up to date on the news on the spread when it gets identified in Washington. There will be, I’m sure, a lot of movement. I mean, there’s already a great partnership of organizations that are thinking about this and what we’ll do in that scenario. But, you know, there will be more resources available to those who will be affected for sure.

Erin Hoover (27:53)
Well, thank you so much for joining me. This was very informative, and I’m hoping it’ll educate lots of people on what to look for and what not to worry about when it comes to Emerald Ash Borer.

Patrick (28:04)
Thanks for having me. I appreciate it.