EAB: There is No Silver Bullet

Emerald ash borer (EAB) was first detected in Minnesota in 2009. Over the last 17 years of management efforts EAB has kept everyone on their toes as we have prepared for its inevitable arrival throughout Minnesota. EAB experts Jonathan Osthus and Mark Abrahamson join this episode of Smarty Plants giving a look back when EAB first arrived and what has transpired since. 

Smarty Plants is a podcast of the Minnesota Department of Agriculture. Visit www.mda.state.mn.us/plants-insects/smarty-plants for more episodes. Look for a new episode of Smarty Plants every month.

Transcript

Jennifer Burington: 0:20

Welcome to Smarty Plants, a Minnesota Department of Agriculture podcast informing listeners about invasive species that affect our environment and agricultural resources. My name is Jennifer Burington, and I will be your host. Emerald ash borer, or EAB, was first discovered in Minnesota in 2009. Since then, it has spread throughout much of the state and has had a major impact on Minnesota's ash trees. With EAB now confirmed in 60 counties, continued awareness and prevention efforts remain critical. To learn more about the pest itself, listen to episode nine of Smarty Plants titled "Living with EAB," which explores EAB biology, impacts, and management in greater detail. Joining us today to discuss emerald ash borer are Mark Abrahamson and Jonathan Osthus. Thank you both for taking the time to speak with us today.

Jonathan Osthus: 1:13

Thanks for having us. Yep, you bet.

Jennifer Burington: 1:15

Mark received his bachelor's in biology from UW-Eau Claire and a master's in entomology from SUNY Syracuse. He started at the MDA in 1999 as an entomologist and has held roles in the Plant Protection Division as a unit supervisor and assistant director before becoming PPD's director in 2018, a position which he holds today. Jonathan is the emerald ash borer technical assistance coordinator for the MDA's Plant Protection Division. He began working on the early detection and management of emerald ash borer shortly after it was first found in Saint Paul in 2009. So to get us started, John, can you s- explain how EAB spreads and what the early signs of infestation are?

Jonathan Osthus: 2:03

Yeah. So there's, uh, two different types of spread. We have human-assisted spread, and we have the natural spread of the insect. So for natural spread, uh, emerald ash borer will often, uh, emerge from ash trees and reinfest the same tree or another tree nearby, but a small proportion of the, uh, population will strike out longer distances. Uh, and the, the average spread rate ends up being about one to two miles per year for natural spread. Um, the actual flight capacity of the insect, um, they can fly, uh, u- up to six miles in a day. Um, but like I mentioned, that average spread rate, uh, for natural spread is about one to two miles a year. Uh, then there is the human-assisted element, where if people move, uh, things like infested firewood or infested ash logs long distances and can, uh, have emerald ash borer jump, uh, you know, from dozens to hundreds or even thousands of miles away. Uh, and so, uh, the early detection signs you wanna look for if you're trying to spot emerald ash borer early on in a tree is you wanna look for, uh, woodpecker damage. So when woodpeckers go after the insects underneath the bark of trees, um, when they're going after emerald ash borer, they'll, uh, slough off some of the outer bark in what we call blonding. So you'll have these kind of blonde patches in the, the mid to upper canopy of an ash tree early on with, uh, small, shallow, dime-sized woodpeck holes where they've gone after the insect underneath the bark. Uh, that's one of the main things that we use to try to detect emerald ash borer early. Uh, some other things that you might see is a thinning canopy. So, um, when emerald ash borer is attacking an ash tree, the trees, uh, tend to die from the top down. And so you'll see, uh, fewer leaves, smaller leaves, more light penetrating through that canopy and, and that canopy dying from the top. Uh, and along with the canopy decline, you'll also see things like bark splits, so these, these vertical cracks in the bark, uh, where that tree is, um, started to grow and heal around that initial emerald ash borer gallery, creating this callus tissue that continues to grow, and the bark separates from the surface of the wood and creates a nice vertical split where you can see that nice serpentine, uh, gallery that emerald ash borer makes underneath the bark.

Jennifer Burington: 4:10

Well, thanks, John. That's very descriptive of what people should be looking for in their ash trees, uh, if they have some on their property. So we've, we've learned over the, over the years to look for woodpecker damage, but what did the early days of responding to EAB look like, uh, in terms of detection and survey methods, Mark?

Mark Abrahamson: 4:31

Yeah, the, uh, I mean, detect- de- detecting emerald ash borer has been a problem from the beginning because you, you, like John was talking about, you really don't detect it until it's kinda too late because it's already there and it's in, uh, numbers high enough to be damaging trees, and, you know, so we're always have been playing catch-up. So I, I, I first got involved with emerald ash borer I think like in 2005. So it was found in Michigan in 2002, and we started looking for it in Minnesota in 2005, and we would have the opportunity to go to, uh, workshops in Michigan and like see infested trees, and so that's, for me, that's always been a really important thing is to try to pass on that 'cause there's like, there's no, no way to beat that experience of seeing it with your own eyes. And so, um But that when we would go to a workshop that like I would, I would always be like, "Okay, I'm looking at a tree. How would I tell if this is infested or not?" That I w- you know, the group would be, you know, uh, peeling, uh, bark off and looking for galleries and whatnot, and I would be wandering around looking at the other trees in the area like, "Well, how would I know if this one is infested or not?" So I, for me, like the visual symptoms cues has always been really interesting. And so I mean, we did other things as well. There was a lot of work, uh, put into trapping. Uh, the problem is we don't have great attractants for emerald ash borer. I mean, we, we… There were some, some tools developed, have had some success, um, over time, but like pretty limited in terms of, of actually trapping emerald ash borer in terms of a detection program. Um, in Minnesota, like, you know, probably because I was so interested in, in trying to find, uh, EAB looking at trees, we really honed in on the woodpeckers. Um, other folks also did, uh, branch sampling. So it was something that, uh, really kinda came out of Canada in terms of like, um, operationalizing, uh, branch sampling as another way to look for emerald ash borer. So branch sampling, basically cutting off branches and stripping off the bark, looking for the, the larvae. So, um, at some point, we actually, we did a study. We worked with the university. Um, we got funding through the state of Minnesota, and we did a, we actually did a study looking at, uh, visual assessment of trees for the woodpecking, branch sampling, and trapping. And, uh, you know, from our study, uh, visual survey was like the most bang for your buck. It's not perfect, like you're, you're, you're gonna miss things. But in terms of like the resources you're expending, that is like the, the best way to, to find it. And so that has been, you know, something we've been passing on to communities and, and others we're working with, um, over time to, you know, try and help them get up to speed with, you know, how do you find it, which is kind of the starting point.

Jennifer Burington: 7:11

Yeah, I have many fond memories of walking around in the, in the winter- Yeah … looking for woodpecker damage on ash trees and peeling the bark for those branch samples. I think John also.

Jonathan Osthus: 7:21

Yeah. I, m- fond memories and- Uh, you know, probably could've built, built a couple log cabins with the, uh, amount of trees that we've peeled, but-

Jennifer Burington: 7:31

I think so- Yeah between the three of us- Yeah … at least here in the room. Yep, that would probably make a cabin. Miles. Or a few. Miles

Mark Abrahamson: 7:38

of logs.

Jennifer Burington: 7:39

Miles and miles, yes. So, um, what lessons have, has Minnesota and other states learned from responding to EAB infestations? I know you talked about, um, the work that we did on how to detect it and stuff, but, like, in response, I know some states have done more, some states have done less, um, and different options.

Mark Abrahamson: 8:01

Yeah. So, you know, um, or r- initially when emerald ash borer was found in Michigan, there was a very aggressive approach to try and, um, eradicate it through re- removal of trees, and the, the-- what killed that was the, the, uh, how hard it was to detect it. So you-- We, we just were never able to catch up to it to the point where they could, they could get their arms around it and get rid of it that way. And so when emerald ash borer showed up in Minnesota, it was kind of at a weird point where that effort had failed, and I think in other places, they were kinda like,"Well, what are you gonna do? There's not, you know, you d- there, there isn't really anything you can do." We kinda took a middle ground where we, um, recognized we're not getting rid of it, but, like, if we can be really aggressive, perhaps we can slow it down, buy ourselves some time. And so, uh, particularly in those early years when we had a limited number of, uh, infestations, limited number of communities we're dealing with, and communities that had some resources to put towards forest management, and we were r- really, uh, encouraged them to be aggressive with finding and removing trees. That was actually a- another study we did with the university, the impact of that work, and we, we did… You know, we can-- We bought some time in terms of, like, the, the, you know, that spread of emerald ash borer and growth out of that area. Um, but at the same time, you know, the story ends up kinda being the same. It just may be, uh, here it's taken a little bit longer than it has elsewhere. So I think, to me, the moral of the story is, like, you, you have some ability to, um, dictate, you know, how emerald ash borer plays out in your state or community or whatever, but, um, only some ability because it is also kind of a, a force in, force in nature.

Jonathan Osthus: 9:40

Right, and I think we've learned that you should be planning for the arrival of emerald ash borer before it shows up in your community, if at all possible, um, and begin taking actions like reducing the amount of ash resource that you have, um, in public right of ways and things like that, and, um, really trying to communicate as much as pop- possible with your residents, um, of what's gonna take place with the ash trees and what the, the outcome will be and that your ash tree isn't necessarily special, and it's not gonna be missed by this insect, so, um, make a plan for it.

Jennifer Burington: 10:12

Perfect. So John, if you want to kind of talk a little bit more about, uh, local agencies, residents, and community partners, um, can, how they can help, um, early detection and prevention efforts.

Jonathan Osthus: 10:25

Right. Um, well, coming to things like the emerald ash borer field workshops that we put on has been really useful for, um, engaging with, uh, public works folks and other interested community members to kind of get them, uh, familiar with early detection. So how to spot that woodpecker damage, how to identify the insect galleries, and taking that back to their community and, and keeping an eye on the trees there so that they can find it at least, you know, when the sympti- symptoms start to become obvious. Um, and then just having other trusted sources, resources, and messengers for, um, spreading the word about emerald ash borer in their community has been a, a really big part of that and what they can continue to do to help, uh, get that word out to residents so that they know that their trees are gonna be impacted and they can start making a plan.

Mark Abrahamson: 11:11

Yeah, and I'd say, like, the, the biggest thing, I-- like, don't be surprised, I would… is kind of my advice to people. Like, it-- this is something that is, is gonna reach all parts of Minnesota. The timeliness for that is, you know, it's still to be determined, and I think one of the things we've seen in Minnesota is perhaps it has moved more slowly, um, you know, than it has elsewhere, but it's still moving. But, you know, you, you, you've got, uh, ability as, uh, the owner or manager of whatever trees are under your care to, like, have a plan for when, you know, that inevitability is gonna occur and, you know, to be prepared to, to take some steps. And there are options, you know, if somebody has an individual trees or a few trees of high value, insecticides are a great option to protect those trees. And if, um, you know, if it's a situation where insecticides are not a good option, uh, you know, you, you're gonna be planning to-- that, that tree or trees are gonna die, and are they trees that are gonna be threatening a structure or human safety? If they are, you're gonna need a plan for how you're gonna get rid of them. Um, if they're not, then maybe, you know, nature can just take its course, and, and they'll, they'll die and fall over. But, uh, I think y-y- you know, like John said, it, it, it's gonna get to your tree too. So you should, you shouldn't be surprised when that happens, and you have an opportunity to plan in advance for, um, you know, how you're gonna handle that. But that's, those are kind of your three options. Either the tree's gonna die and fall apart, you're gonna have it cut down or cut it down, or you'll, you preserve it with insecticides.

Jennifer Burington: 12:41

So those are the kind of the three options. And you talked about, um, kind of it's moving slower in Minnesota, so can the cold temperatures slow EAB spread, or has the insect shown that it can adapt?

Mark Abrahamson: 12:56

Yeah. So there's a couple of ways the cold can affect emerald ash borer. So one is just how long it takes it to complete a generation, so the time from when an egg is laid until a new adult beetle crawls out of a tree. And for emerald ash borer, that can take one to two years, and that's really, uh, dependent upon how much, uh, temperature they're accumulating during that time. So, um, the warmer it is, the more likely the insects are to complete their development in one year. The cooler, uh, more likely it is to be two years. So I think in Minnesota it's probably 50/50, would you say, in terms of- In

Jonathan Osthus: 13:27

the metro area, it's even higher for a two-year life cycle in northern Minnesota.

Mark Abrahamson: 13:30

Up north. Okay. Yeah. So right there, that's, that's cutting it in half, like how quickly they're gonna be building up is just that, that taking an extra year to complete their development. And then also, uh, during the winter, if it gets cold enough, it will outright kill larvae, um, which we've been really interested in that. It's another, um- A line of research we've done working with the university on, uh, winter mortality. And yeah, it has an impact. It probably has helped to slow the population growth in Minnesota, but it doesn't get rid of it. So there's not a part of Minnesota where we're gonna expect that emerald ash borer can't exist because it's so cold, but it also may move more slowly through the north. Yeah.

Jonathan Osthus: 14:09

It opens up more opportunity for aggressive management in some of our more northern communities as well that could be more effective at slowing the rate at which that, um, you know, ash mortality occurs. Um, and, you know, if you have a two-year life cycle, that's more time for woodpecker predation and, and other, other factors to kill the, the larva.

Jennifer Burington: 14:27

Perfect. Well, since moving firewood, uh, is a major pathway, John, that you talked about, uh, earlier for spreading EAB, have outreach efforts like, uh, the Don't Move Firewood campaign improved public awareness over the years?

Jonathan Osthus: 14:42

I would say yes. Um, so there has definitely been an uptick in calls and questions about, um, certified firewood. So, uh, the MDA, uh, certifies heat- uh, heat-treated firewood, which is, uh, allows it to move freely throughout the state, um, and go outside of the emerald ash borer quarantine areas or spongy moth quarantine areas. And I've just noticed a increase in calls of regular residents, uh, inquiring about is it safe to move firewood from point A to point B? A- and just kind of wondering how that works. So people are much more aware of the actual regulations that exist and, um, that it's a major factor for spreading pests, and that's been a pretty big change over the last 15 years.

Jennifer Burington: 15:25

Yeah, we've been s- spreading the message about Don't Move Firewood and Buy Local Burn Local, um, Firewood too, to kind of hone in on, um, Minnesota business and stuff also, uh, to help with that. So episode 14 of Smarty Plants, uh, is dedicated to EAB biocontrol for listeners who want more information. But John, can you share how successful these efforts have been so far? I know we've released three different species of, um, non-stinging parasitoid wasps. Has biocontrol in Minnesota.

Jonathan Osthus: 15:58

Yeah. So it's kind of an invol- evolving story. So we began doing, uh, biological control releases in 2010, uh, in the kind of far southeastern part of the state in Houston County on the Mississippi River. And from there, we've now released at over 54 sites, uh, in 19 counties and on, uh, tribal nation land. And so what we've seen is that they are able to establish. They're, they're establishing, they have reproducing populations. Um, they are persisting over time, uh, and we are seeing, uh, their populations increase at certain sites where we've done more intensive monitory- monitoring. Uh, one thing that's been noticeable, um, is that because we have a lot of the insects, um, taking that two-year life cycle, so taking two years to complete that life cycle, we-- that, that's important for the parasitoids, um, that we're releasing because they are dependent on those late instar emerald ash borer larvae to be present in the spring, um, when they emerge before emerald ash borer does, uh, to be able to reproduce. And so in states that have more of their emerald ash borer, uh, completing their life cycle in one year, th- those larvae aren't present when those, uh, parasitoids initially emerge. So that, that's a very important factor that's, uh, helped our, our biological control program, uh, continue to see some success. So it's important caveat for this is that it's not gonna protect the mature trees as the initial wave of emerald ash borer comes through. Um, those large mature trees are still gonna be killed by emerald ash borer in that initial wave. Uh, this is really kind of a strategy to try to keep ash in the system in the long term, so when you start to have ash regeneration, be able to protect those smaller trees as they grow to sizes that can then put out seed. So, um, we're still somewhat early on in terms of, of biocontrol program, and w- you know, we're gonna find out more over the coming years, uh, and see if they're able to actually suppress emerald ash borer populations, uh, enough to keep ash in the system in the long term.

Jennifer Burington: 18:02

Perfect. And that's just one of the tools that is commonly used, like we talk about on that episode, in large forested environments where you're not gonna go in and- Right remove trees like Mark was talking about or use chemicals, any type of that treatment. So it's, it's kind of a, an assistance with the management- Right … but it's not gonna solve the EAB problem.

Jonathan Osthus: 18:22

Yeah, and it's, uh, kind of a sustainable management practice where- Yep … you know, you get something established, and it moves with emerald ash borer as it moves into new areas.

Jennifer Burington: 18:30

Perfect. And Mark, what advice would you give communities that are just beginning to deal with the presence of EAB?

Mark Abrahamson: 18:39

Yeah. Well, you know, we'd, uh, uh, really proud we put together a really nice set of guidelines, I think, for communities several years ago as a team, which, um, kinda outlines what, you know, an approach from the beginning to the end. And so the beginning of, um, having emerald ash borer in a community is really your opportunity to be aggressive and try to limit the, the, the increase of that population, uh, limit its spread by, you know, being vigilant about, uh, trying to find, uh, infested trees and then either getting them off the landscape or getting them treated with insecticide. But anything you can do in those early stages to affect the, the trajectory of that population growth is gonna buy time for the rest of your trees because it's a, it's a direct relationship from how many emerald ash borers there are to how fast your trees are dying because it's the, it's the, the chewing of those beetles that kills the tree. And so the more beetles there are chewing in the trees, the faster they're gonna die. So anything you can do to, to slow that down is gonna buy you time and, uh, help you keep trees on the landscape longer. But as you, you, like we talked about earlier, there's, there's an opportunity to delay things, but it is also kind of an inevitability that there's a bad outcome at the end. So as you move through an infestation, the-- I think your, uh, priorities kind of shift to where, okay, you know, initially we're trying to be really vigilant about keeping emerald ash borer under wraps as much as possible, but, you know, as it gets more established, then it might become more about like how do we manage all this wood that's being generated in our community and, and how do we deal with it so it's not, uh, moving somewhere else and spreading the infestation, but then also perhaps, you know, providing some value to us, uh, as well from, um, wood products or, or mulch or whatever. So, um, so anyway, I think, you know, there's, there's a, kind of a range of, of approaches and, um, you know, where you are with the infestation, um, you know, your approach kind of changes.

Jonathan Osthus: 20:35

Right. There's, like we've mentioned, there's no silver bullet for this, so using multiple management tactics to address things, um, uh, re-really and just, um, take action. Uh, doing, doing something is a lot better than doing nothing in the scheme of things. And, you know, um, keep an eye out for grants that are available. There's been consistent funding over the last seven or eight years from, uh, the DNR Community Forest Program, uh, for communities to apply for funding to help with the cost of removals, uh, replanting, replanting with a d-diverse set of species so you don't have, um, all this monoculture of so many of one species that, uh, will leave you better off for the next pest that comes through.

Jennifer Burington: 21:19

Yeah, and then the book that Mark, well, I shouldn't-- Yeah, the in- the guidelines, the EAB, uh, management guidelines is available as a PDF on our website. Um, if you go to the MDA website and look f- search for emerald ash borer, it will be on there for that you can download it. Um, there's some great pictures of the different woodpecker damage, um, a nice chart on how to, uh, determine kind of where you are in the stage of emerald ash borer management, if you have it yet or if you don't, um, what type of environment you're gonna be working in, and different suggestions, um, based on those different criteria. So, uh, it's a nice publication. I know a lot of communities really enjoy, uh, reading it, so especially so that they understand everything that's available, um, that they can do or, and all, all these options, and then they can choose what is best for their community.'Cause you guys have talked about all the different options: removing trees, treating trees, um, proactively looking for woodpecker damage, um, bark, um, peeling the bark off the trees to look for those galleries underneath. Um, a lot of things that, uh, communities can do. Um, what are the biggest priorities for EAB management, uh, moving forward?

Mark Abrahamson: 22:32

You know, I think it, uh, kinda like we were, were, uh, talking about, it depends where you are and kinda where you, you know, what stage you are with emerald ash borer. And so for us as an agency, we're, uh, we're, our focus is more on the, the new areas, right? Because that's kind of our job is to try and find those new areas, know where emerald ash borer's occurring, try and limit them from getting to new places. And so, um, you know, if you are, uh, uh, you know, one of those communities that's out on the fringe where emerald ash borer really isn't invaded yet, I mean, de- detection should be, you know, one of your, your main things is making sure you know how to recognize it and, um, you know, have like some kinda system for, uh, keeping an eye out for it. Um, you know, citizens and, uh, outreach to folks is a great way to do that. Um, but if you are, you know, a community that's more, like it's been there for a while, you got a whole different set of priorities and, and problems that you're dealing with.

Jonathan Osthus: 23:27

Right. That's more in the utilization category. So how can I make use of all this wood waste? Um, can we make, uh, you know, furniture? Can we make cribbage boards, things like that, is ways to keep it out of the, the wood waste stream to, as, you know, tipping fees can be really expensive in the metro for getting rid of, uh, tree waste. Um, and yeah, uh, if you're out on the fringes where you're not yet being impacted by EAB, uh, planning. Uh, if you're in a community, having an inventory, uh, in your town or on your own property, uh, if you're a private woodland owner, uh, reaching out to your area DNR forester, that can help you out. If you're looking f- for management options and maybe some silvicultural guidelines and things like that, um, those are all good steps to take, uh, to prepare for the inevitability of emerald ash borer, um, reaching you at some point.

Jennifer Burington: 24:17

Yeah, the inventory really is the key to what starts it all. You have to know how much ash you're gonna be dealing with, um, and where they're located. Right. So-

Jonathan Osthus: 24:26

Mm-hmm… Jennifer Burington: yep, starts it all. It's hard to manage w- if you don't know what you have.

Jennifer Burington: 24:29

Yep.

Jonathan Osthus: 24:30

Yeah.

Jennifer Burington: 24:31

It's hard to come up with a final number for the community to know, like, "This is how many we're gonna have to manage, and this is how much it's gonna cost." So, all right. Do either of you have any final thoughts about EAB and its future in Minnesota?

Jonathan Osthus: 24:46

I mean, we, we kinda covered it. It's, it's gonna eventually reach everybody. Um, it's gonna continue to spread, uh, hopefully at slower rates i- in the more northern parts of the state, especially in areas where we have really large black ash resource. But, um, like I said, uh, planning for its arrival is really key, so, uh, don't be caught off guard.

Mark Abrahamson: 25:08

Yeah, what are we at, uh, you know, at 60, about counties, uh, out of 87, so we're, uh, you know, we're approaching, you know, not too many years in the future where it will be found in every county. But just having it present in a county doesn't necessarily mean, um, a big impact. So there are, uh, you know, there's that opportunity even after it shows up in a county to still take some action, um, you know, use all those tools we talked about, insecticides, removals, et cetera, to try and, uh, preserve trees, um, you know, even if it's just to, you know, for it- the time being. Um, so I think, uh, you know, it's hard because this has been such a, a long-term thing. It's hard to keep it in, uh, the forefront of your mind because there's a lot of, lot of things to worry about in life, right? And this is, um, something that's played out over years and years and will continue to play out over years. But, uh, it is, it is, uh, it will continue to be a thing, um, you know, for many years to come, so.

Jennifer Burington: 26:05

Perfect. And then as people are, um, out in their community, and especially in those new areas that haven't detected EAB yet, uh, if they do happen to see, um, the signs that John was talking about, like the woodpecker damage, um, the thinning canopy, you can always, uh, contact the MDA's Report A Pest line. Um, and if you have pictures to send in of the ash trees that you're worried about, uh, John can take a look at those. Um, all of the EAB, uh, reports get directed to him, and you can find the information for our report, how to report in to us by phone, email, or our online form online at www.mda.state.mn.us/reportapest. It's all one word. Well, thank you so much, uh, to both of you. It's truly been a joy talking to you both. I certainly learned a lot, and I'm sure our listeners did too.

Mark Abrahamson: 27:00

Thank you.

Jennifer Burington: 27:01

Yeah,

Mark Abrahamson: 27:01

thanks.

Jennifer Burington: 27:02

This has been Smarty Plants, a podcast from the Minnesota Department of Agriculture. Our producers are Brittany Raveill and Sadie Anderson. Our editor is Larry Schumacher, and I have been your host. You can learn more about pests and other invasive species that affect our environment at www.mda.state.mn.us/plants-insects. And while you head to our website, we'll be working on the next episode of Smarty Plants. See you there.