S5E1: How do we protect our forests from invasive species?

The invasive browntail moth exploded in Maine this summer. It damages and kills trees and causes rashes and respiratory problems in humans.

The moth, however, is only one of many invasive species that plague Maine forests. University of Maine entomologist Angela Mech helps combat these unwanted visitors from the front lines, and she and her team may have a solution for dealing with browntail moths.

In this episode of “The Maine Question,” Mech discusses her work helping communities in Maine manage browntail moths and other invasive species, such as the spruce budworm.


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Ron Lisnet:  Hello, welcome to “The Maine Question Podcast” as we begin season five. I’m your host, Ron Lisnet. We are pumped to share our stories with you this season.

There’s so much interesting work happening at UMaine and labs, and classrooms, in the woods and really all across the planet, that it’s hard to know where to begin this new season.

Our first story out of the gate takes a look at the forests of Maine, and some of the pests and plagues that threaten them.

Angela Mech:  If we look at Maine forest, and we compare it to for example, the forests experiencing Megafires out West or the Pine Barrens of New Jersey. Our forests are great, but the term health is subjective.

Ron:  That’s Angela Mech, an Assistant Professor of Entomology at the University of Maine. She studies bugs, specifically the bugs that infest our forests in Maine. That means she is very busy, indeed. Some of those pests are fairly well‑known. Spruce budworm, for example, is a pest that has been in Maine before and is on the rise again.

Many of these insects can harm trees and affect the industry, but they don’t directly affect the general public. The latest plague that has grabbed headlines in the summer of 2021 certainly broke that mold. The browntail moth is a rare triple threat in the bug world.

It can affect the ecosystem. It can harm the forest products economy, and the thing that made the public pay attention, it can cause harm to anybody who comes into contact with it by causing itching, rashes, and in some cases, much more serious medical conditions.

This bug has occupied much of Angela’s time in 2021. She’s worked with communities around Maine to monitor the browntail moth population and to try and figure out how to control its numbers. The good news is that she and her team are helping to develop a potential new weapon to curtail this pest in a way that is effective and friendly to the environment.

We talked about that research and about some of the other bugs and outbreaks she encounters in her work, including the latest development. A first in the United States Facility to help landowners and the public deal with the coming spruce budworm outbreak. We spoke about these challenges just as she was finishing her fieldwork late this summer.


Ron:  Angela, thanks so much for taking the time to join us. I know it’s a busy time for you being out in the field, doing your fieldwork and all the research you’re doing, but appreciate you joining us and telling us what you’re up to.

Angela:  Thanks for having me.

Ron:  Set the scene for us. What is the current state of the health of forests in Maine and beyond, if you want to talk about that? How big are the threats they’re facing? How are things trending right now?

Angela:  If we look at Maine forest, and we compare it to, for example, the forest experiencing mega fires out west, or the Pine Barrens of New Jersey, our forests are great. The term health is actually subjective. It depends on who you’re talking to.

Some folks consider a forest healthy if it meets the management objectives, like for a timber industry. Some folks consider it healthy, if it is a fully‑functioning ecosystem. It’s more about the big picture, than specific species.

Then, there are others who consider a forest healthy if it has the ability to bounce back or recuperate from a big disturbance, or a stress. Based on all of those criteria, I would still say that Maine has very healthy forests. We are meeting management objectives.

I see a lot of vitality, and fully functioning ecosystems. Maine is definitely not going to be spared from climate‑change effects. It’s not going to be spared from invasive species. When you think of the big picture and the beyond, it’s definitely going to be changing. That is the one constant with all forests.

Forests are always going to be changing. We’re going to see new changes across the landscape.

Ron:  You are an entomologist. That is a person who studies bugs. That’s what you do. I’m glad we defined our terms, that’s good.

Angela:  [laughs]

Ron:  Unfortunately for the forests, but maybe fortunately for folks in your line of work, that are trying to get into the field, there seems to be a lot of work these days. The number of pests and bugs that are plaguing forests and other things does not seem to be going down.

Angela:  Unfortunately, you are correct that there is a lot to keep us busy. Right now, in North America, there are about 1,500 non‑native insects that feed on our plants or can cause damage. About a third of those are in our forests. Almost 500 species are in our forests that aren’t native to our area.

If you think about it, not all of them are bad. If there were 450 really bad insects, we definitely wouldn’t have enough entomologist in the country. It’s about less than 10 percent of those actually cause a lot of impacts in our stance. It’s the ones that folks may have heard of like emerald ash borer and hemlock woolly adelgid, and the moth formerly known as gypsy moth.

We still don’t have a new common name for it. Those few species, less than 10 percent, cost us billions of dollars, and that’s everybody paying into it at the federal level, at the city level, at the homeowner level.

Our job is to try and learn as much as we can about these species. Figure out how to help control them, how to manage them. It is a great opportunity for research. If there are students that really enjoy being out in the field and being able to test different things, then forest entomology is a wonderful field. I’m very glad that I chose this as my career.

Ron:  Let’s talk about what keeps you up at night. The biggest threats out there grabbing headlines. Let’s start with the browntail moth, which has grabbed headlines this past summer 2021. What is the trajectory of this pest? How big is the infestation? How is it growing right now? Is Maine an epicenter?

Angela:  Browntail moth has a very interesting history. It’s actually been here for over 100 years. It was first detected in the 1890s, and it was detected in Massachusetts and spread across New England, Northeasterly and covered Maine into New Brunswick Funland and went over to New York.

That massive outbreak lasted for about 15 years and then retracted. People could only find browntail moth in Casco Bay, Maine and Cape Cod area of Massachusetts. Browntail moth is interesting in that it has these growth spurts. It’s a natural part of its lifecycle. It’s from Eurasia and in Eurasia, it also has these population growth spurts.

We refer to that as a cyclical out breaking pest. It’s not a constant outbreak. It happens every so often. In Maine, we’ve seen these growths but this outbreak is the once‑in‑a‑hundred year outbreak. We’re seeing the expansion going into areas that haven’t seen browntail moth since that initial outbreak a hundred years ago.

It’s now covering about a third of the state, most of the coastal areas where it started, and it’s been spreading inland. Here in Orono, we now have browntail moth, and this past summer I saw more moths than I’ve ever seen in this area. It doesn’t seem to be declining.

As far as the trajectory at the moment, it is still going strong. I think we’re going to be dealing with browntail moth for a little bit time more. Further inland folks should be prepared that they may also be finding browntail moth on their property.

Ron:  For those that haven’t had the misfortune of being afflicted by browntail moths, tell us, what does it do to the trees, and what does it do to people or other creatures out there? You described, I think, a trifecta of threats. What does that mean?

Angela:  Browntail moth is unique. I usually deal with tree insects, which can have ecological impacts because they’re attacking a tree, killing a tree species, affecting ecosystem, or having cascading effects. Browntail moth has a very large close range. It feeds on over 80 species of trees and a slew of families.

It prefers oaks, for example, and it will defoliate and kill oak trees with repeated defoliation. We have to think, “OK. Well, what about all of the mammals that are dependent upon acorns for part of their diet?” If we lose a significant amount of oaks, we’re going to have these ecological impacts from browntail moth that cascade.

A lot of tree pests have ecological impacts. We have economic impacts of pests. Those are insects that are attacking and damaging trees that are utilized for the timber industry that have an economic value. Feeding by an insect might reduce growth rate or apple orchards. Browntail moth unfortunately loves apple.

We’re seeing impacts in that industry as well. Then recreation and tourism. I’ve been hearing nightmares from folks where outdoor events are having to be canceled or moved because of browntail, that people are canceling their reservations because it was during browntail peak time period.

Lots of economic impacts, but the big one that most folks know about is the human‑health impact. That’s what makes it the trifecta ‑‑ economic, ecological, and human health. For us humans, unfortunately, they have little tiny barbed hairs that have a toxin in it, and those hairs go airborne every time they molt.

They molt about seven times during their life cycle. Those hairs get stuck to us with the barbs, and the toxin goes in and creates a poison ivy‑like rash, which I learned very early on I am not immune to, and can even cause respiratory issues from inhaling them for people with sensitive systems. It’s a beast. I’m not a fan of it. [laughs]

Ron:  I guess you have to respect how effective it is at doing its job in a way.

Angela:  It has figured out a way to be highly successful at what it does.

Ron:  Talking about how to battle this pest, I know you’re looking at a new way to combat this moth. Can you describe what you and your colleagues are trying to do to knock down moth populations? Any early results? Basically, you’re the opposite of a dating service, right?

Angela:  [laughs] Yes. For part of what we’re doing, exactly. One of the big bummers is that because browntail moth hasn’t had an explosion like this in over a hundred years, there hasn’t been a lot of research regarding browntail moths. If you dig through the scientific literature, there’s less than five articles were written in the last 20 years.

It’s not that well‑studied, which is great for me, because it means there’s so many possibilities. One of the things that we’re most excited about ‑‑ we’re testing a number of things ‑‑ is a semiochemical control method, which is basically using pheromones.

In entomology and agriculture systems and forest systems, pheromones can be used to manipulate insect populations because all insects are using pheromones. The pheromones are very specific to a single species. Pheromones are only used to communicate within the same species.

One thing that was studied about 30 years ago, really starting to get into, is using sex pheromones as a mating disruption technique. It was highly successful with the gypsy moth, and it is currently used for the federal Slow the Spread program.

What we do is we want to inundate an area so that there is so much of the female sex pheromone in the area that the males can no longer find the females to mate, which in turn causes the population to crash in that area.

It’s highly specific, there’s no environmental impacts or non‑target effects, which we do have with the chemical pesticides. We’re looking at killing a lot of the insects, not just the insect that we are focused on, and it can be even cheaper than chemical treatments. If it turns out to work, it’s a very good step in hopefully bringing the populations down in Maine.

Ron:  Are the early results encouraging, or?

Angela:  Yeah. We are working with TrÈcÈ Incorporated, which is a company that is synthesizing the pheromone. The sex pheromone has been identified, and this summer we did a pilot study to test that synthesized pheromone to see how effective it was during this summer’s flight season. We tested different purities of the pheromone, and different types of traps, and got some very strong results.

There definitely is a favorite for the males. There was a particular lure that they were more attracted to. Even one of the traps was better at trapping them than the other. We’re going to take these results and work with TrÈcÈ to increase the dosage of that and start testing if we can confuse the males.

Ron:  Let’s talk about some other threats that are out there. A lot of these, unlike the browntail moth, don’t affect public health like that pest can. They certainly do a number on tree populations in the forest industry. Give us a very brief rundown of some of the ones that people maybe have or haven’t about in the news.

Spruce budworm, emerald ash borer, hemlock woolly adelgid. I think I said that right. Those are some of the big ones, right?

Angela:  They are some of the big ones. Hemlock woolly adelgid, I’ve worked with now for almost, it’ll be 20 years next year, so that’s been my personal nemesis until browntail moth is my new nemesis. Our eastern hemlocks are threatened by HWA, as we refer to it. It is a slow killer, so if you do find hemlock woolly adelgid on your trees, there is a lot of time to save those trees.

Emerald ash borer is a recent invasion within the last few years. Right now here in Orono, it hasn’t been detected, but it has down in the southwestern part of the state. All ash species are threatened. It’s a wood borer and it can cause mortality in a couple of years, so it’s a much quicker killer.

Spruce budworm is actually a native species, so it’s native to North America. It can kill our spruces and firs, it defoliates the needles, so it is a big pest in the timber industry, especially up in the north Maine woods area.

Ron:  I know that the University of Maine has a long history of dealing with spruce budworm. I know that there was a big outbreak I believe in the ’70s, and here we are again. I know that you have a lab that is being put up and ready to go to help deal with this pest and help the industry. Can you talk about some of the new developments in the battle against spruce budworm?

Angela:  Back with the last outbreak, they developed a process to try and determine whether a particular area or stand was going to have an explosion. Whether the outbreak was in a particular area. What that did, it created a model that based on the second instar larval stage, however many you had, determined your outbreak potential.

If you had more than seven ‑‑ seven is the magical number ‑‑ L2s, as we refer to them, means that you should be prepared to have some treatment in the following spring. The process for counting those caterpillars, because they are in their silk nests for the winter, it’s a chemical process.

We are opening up the spruce budworm processing lab. It’s going to be the only one in the United States. We do have a couple in Canada that have been processing branches from Maine, but now that the need in Maine has increased for opening up the facility here, we’re going to be ready to start processing hopefully next month.

That will be a service that is available to anybody. All landowners would be able to send in samples. Private, industrial, and agency folks can utilize it as well. We’re excited.

Ron:  Similar to what cooperative extensions is doing with the Tech lab, this is a service that the public or the industry can take advantage of. Let’s do a little basic bio 101 for neophytes like me. You hear about the cyclical nature of these pests, how every 15 years, every 30 years, or whatever that the locusts descend or whatever it happens to be. How do you explain how that biology works?

Angela:  First out, not all insects are cyclical but a lot of them in the forest actually are. That is one of the great mysteries in biology. No, there is no direct answer for all species as to why they outbreak. Most of the thought behind it is that it has to do with natural factors, means trophic interactions.

It has to do with hosts, the predators, or the natural enemies. The whole system that there is a slight shift in the system that causes these populations to increase in abundance and then go back down.

There are southern pine beetle, for example is a great example of an outbreaking cyclical pets where we know in the South that every 7 to 10 years somewhere, there’s going to be an outbreak, spruce budworm.

We know that approximately every 30 years there’s going to be an outbreak and with browntail moth. It’s every 10 to 15 years, although hoping that we’re not going to be having the same conversation in 15 years.

Other insects…There are those that have this natural cycle that we’ve seen through history. All of the records, we can predict. We know it’s coming. Then there are those that increased the abundance based on they develop the outbreak phase based on something that happened.

If there was something that caused a stress to the trees that they usually attack and now there’s this overabundance of food, that can cause an outbreak or a disturbance. If there’s a windstorm and now all of these stressed and fallen over trees that can cause an outbreak.

The example that I always think of is the hemlock worm. It’s a native wood boring insect. It’s usually just a secondary pass and doesn’t do anything. When hemlock woolly adelgid first kicked in and started stressing out all of the hemlocks.

We had this hemlock for outbreak that we had never seen before, and it ended up basically putting the nail in the coffin for a lot of hemlock trees that were stressed out from HWA.

Ron:  Been a long time since I sat in a biology class, so thanks for the explanation.

Angela:  [laughs]

Ron:  As with all ecological issues these days, a changing climate seems to play a role. How much does that factor into the browntail moth or some of these other pests you’re talking about or just big picture, it seems like changes are happening faster than the forest itself can keep up with?

Angela:  All insects are poikilotherms, which is a big fancy word for they do not regulate their body temperature. They’re not warm‑blooded animals, like us. This means that any change in climate is going to affect an insect. No matter that change, whatever the changes in climate is going to affect an insect.

There are some effects that are very direct, like a warmer winter is going to increase their survival over the winter or a longer growing season could add an extra generation to particular species. We have those direct effects and then indirect, it can affect the host.

We’re experiencing a drought. Trees are stressed out by that drought. When trees are stressed, they can’t defend against insects as well. Insects can be more successful during a drought, because the trees are being stressed. Temperatures and climates can also affect the natural enemies of the insect and could either be a stronger presence or less presence.

There are effects of climate with browntail moth. In Maine, we have a fungus that does kill browntail moth caterpillars, it’s called Entomophoga Aulicae. Typically, it would cause a significant decline in browntail moth. It requires cool, wet springs, which is something we haven’t had in Maine in a few years.

That change in climate has helped browntail moths reach the level that it currently is, because there hasn’t been anything to naturally bump it down.

Ron:  Just back to the brown tail moth and the concept that you’ve come up with ‑‑ the mating disruption technique ‑‑ how is that going to be rolled out? I know you’ve been working with some members of the public to do monitoring and trapping, correct? If the concept works, how does that roll out and start to make a dent?

Angela:  In other systems like in agriculture systems or even for other tree pests like Gypsy moth or southern pine beetle, these semiochemicals can be made easily available for the public, or for city council’s, or for states to implement with state funds or federal funds.

For some pests, you can buy dispensers that you can just tack to your trees like get enough based on how many acres you have. Every 10 trees gets a dispenser.

Some companies create a compound that can be sprayed into the canopy and it will slowly degrade. As it degrades, it’s emitting the pheromone. You only need to spray once and it will basically cover that entire area. Even with gypsy moth, they spray using airplanes over across very large landscapes and it’s very successful.

It just sticks to the leaves and slowly degrades, and it covers a very large area. Depending upon the resources that are available to either homeowners or to city councils or to the state, there could be different ways of implementing this to control browntail moth.

Ron:  Just so people realize when you talk about spray and chemicals, maybe people are thinking there’s some nasty chemical. This is a natural substance that only affects the insects that you’re targeting. Correct?

Angela:  Yes, they are environmentally friendly. There is no impact of the spray. It slowly biodegrades and so there’s no residuals, and it is highly specific to just browntail moth. Whereas other, a few decades ago, large spray applications might affect, for example, all caterpillars or all insects or something or affect potentially aquatic systems and lobsters.

None of that would be the case with applying the pheromone. It’s just a pheromone. [laughs] It doesn’t have the negative consequences of our traditional chemical pesticides. It’s more environmentally friendly and it’s more economically friendly, but it is much cheaper for the same rate that one would use for traditional pesticides.

Ron:  What can homeowners do or property owners that, first of all, to identify that they have it? Is there anything they can do to their trees or their flora that they’re dealing with?

Angela:  Yeah. At the moment, our options are limited. The homeowner, what you can do is you want to look for those winter webs. Once the leaves fall off the trees this summer, browntail moth creates a silk and web that hangs out at the tips of branches.

You can see these in the trees, they can reflect the sunlight if you’re standing in a certain direction. If you find any of those webs in the winter, you can clip them and kill them by just throwing them in soapy water or if allowed, you can also burn them. If they’re too high, hire tree care companies can come with bucket trucks to help clip winter webs out of the trees.

If the winter webs are eliminated on your property, you won’t have caterpillars feeding on those trees the following spring. The Maine forest service has some wonderful resources on their browntail moth website. They have videos to show like how to identify the nest and what you can do. They also have a list of tree care companies that will work with browntail moth.

Probably the biggest thing is that most folks don’t realize that they don’t look in the winter and they may not realize they have browntail moth until the following spring when they start itching. Usually by that point, it’s too late to actually treat the trees. You do need to be proactive. You need to look for this.

If you know that you do want to get your trees chemically treated against browntail moth, you need to get on the reservation books pretty quick. I heard this summer, there were many people who called around and all tree‑care companies were booked. Making sure that you are proactive and don’t wait until the last minute to try to get someone to come out.

At the moment, those are our options, clipping the winter webs and chemical treatments until we’re able to figure some new stuff out.

Ron:  Finally, as we wrap up here, simple question, why bugs for you? What drives you to do this work? What would you say to students that were coming here to the university about what the opportunities are or what the field is like?

Angela:  I did my undergrad and I was a plant nerd. To start, my undergrad was in botany. I loved plants. I thought they were so cool and Hemlock was my favorite tree.

Then, as I was wandering around, my undergrad research, I found these white fuzzy things on hemlock and saw the hemlocks die and just realized that if I loved plants, I had to learn about the insects that could kill them.

Therefore, and then study how to kill those insects to save the plants that I enjoy. I thought plants were the coolest until I took my first entomology class, which wasn’t even until grad school.

Then I realized how cool insects were. They’re so fascinating. We can learn so much from them. Here at humane entomology. The cohort is within the School of Biology and Ecology.

We are in the process of adding an entomology concentration and an entomology minor because we are definitely seeing a lot of new faces and folks taking our entomology classes and wanting to learn more about entomology because insects are so cool.

For the state, we will continue to study issues and pests within the state. All of my entomology colleagues here are working on a very important system or pest within the state.

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Angela:  We welcome students to come work with us and fall in love with insects just as much as we did.

Ron:  Certainly sounds like they’re needed. That’s for sure. Thanks for taking the time to share your thoughts and your story with us.

Angela:  Oh, thank you so much for having me, Ron. If anybody has any questions, feel free to email me I’m at angela.mech that’s M‑E‑C‑H @umaine.edu.

Ron:  Thanks for tuning us in. We’ve got a great lineup of stories in the pipeline for Season Five. A new episode will drop every Thursday during the fall semester. As always, The Maine Question can be found on Google and Apple podcast, Stitcher, Spotify, SoundCloud, and on UMaine’s Facebook page.

Have questions or comments drop us a note at mainequestion@maine.edu and consider subscribing. This is Ron Lisnet. We’ll catch you next time around on the Maine Question.