Digging Up Dirt on the Spruce Budworm

Joel Houle If you live in eastern Canada, chances are you're familiar with the spruce budworm, an insect that eats the needles of balsam fir and spruce trees. This feeding weakens the trees, and after a few years, it eventually kills them. As if that wasn't enough, researchers are now looking at the potential impact that spruce budworm outbreaks could have on climate change.

Two scientists from different government departments have hit the ground, literally in this case, to see if this little pest is having an impact on the carbon levels in forest soil. On today's episode: killer insects, scientific collaboration and elaborate cheese plates…

Joel Houle Welcome to a new episode of Simply Science, the podcast that talks about the amazing scientific work that our experts at Natural Resources Canada are doing. My name is Joel Houle. And joining me is my lovely co-host, Barb Ustina. Barb how’s it going?

Barb Ustina Hello. It's going just great. How are you doing?

Joel Houle I'm great. I'm excited! This is actually our 30th episode of the podcast. So I'm really excited about that.

Barb Ustina That's such an accomplishment!

Joel Houle It is.

Barb Ustina You know, really, it is 30 podcasts. Have you ever done a podcast on the spruce budworm before?

Joel Houle So, yeah. I’ve actually interviewed Rob Johns, from our Atlantic Region, who researches spruce budworm, and it was a really interesting podcast.

Barb Ustina Oh, yeah. And have you ever seen a spruce budworm in person then? Like, have you handled one?

Joel Houle No, I wasn't able to. It was by phone. But I have seen a lot of photos and videos. Actually, one of Rob's colleagues, Emily Owens, has this video that she issued over social media last year or the year before. And it's her shaking this tree. And you've got like hundreds of these moths, these little gray moths going up all over her. And she actually picks it up and shows it to the camera. It's really a sight to see.

Barb Ustina It's kind of like it's raining moths, right? They're living on the upper branches of the trees. You can shake down a tree, and they just come tumbling out like that.

Joel Houle It almost looks like snow covering the grass. It's really impressive.

Barb Ustina You know, they are incredibly well adapted to life in Canada. The spruce budworm can actually survive a typical Canadian winter. And the way they do this is that the larvae can hibernate in the nooks and crannies they find in the upper branches of trees. So in the spring, the larvae emerge, and they're ready for action. And for the spruce budworm, that means eating — and eating a lot. And that's how they destroy so many forests. They feast on new needles and buds they find on the fir and spruce trees.

Joel Houle So that's probably why it causes so much damage, because it's all those new needles. It's all those buds. So the trees can't grow, can't get light. Wow.

Barb Ustina Yeah, exactly. It's like an all-you-can-eat buffet for the spruce budworm.

Joel Houle That’s a lovely visual. Thanks Barb!

Barb Ustina Yeah. I hope no one's eating lunch while they're listening to this. Right. Anyway, the spruce budworm — eventually the larvae become brown caterpillars about two centimetres long. And then during the summer months they transform into grayish-brown moths.

Joel Houle OK. Those are the moths that we see in those videos and those pictures.

Barb Ustina And get this! As an adult moth, the female will lay up to 200 eggs on the underside of fir and spruce tree needles. Sounds lovely.

Joel Houle 200. So it's one female, 200 eggs.

Barb Ustina Yeah. And in about two weeks, the eggs hatch and the larvae hibernate for the winter, getting ready for the destructive cycle to begin all over again in the spring. So right now, they're probably hibernating, getting ready for spring.

Joel Houle Wow. Well, I mean, it makes sense that they are causing so much damage to the ecosystem of the forest. If every female can lay 200 eggs, it can, you know, exponentially grow.

Barb Ustina Exactly. I tell 200 friends. She tells 200 friends, and so on, and so on and so on.

Joel Houle It's like a pyramid scheme. Well, you know what? Let's bring in our experts, and they can tell us about the work they're doing with the spruce budworm.

Barb Ustina Absolutely.

Joel Houle Our guests today are Michael Stastny, a forest insect ecologist with Natural Resources Canada, and Louis-Pierre Comeau, a research scientist working on landscape and soil carbon. He's with Agriculture and Agri-Foods Canada. Can you start by telling us a little bit about what you guys do? Let's start with you, Louis-Pierre.

Louis-Pierre Comeau I'm a soil carbon and landscape specialist at Agriculture and Agri-Food Canada. My speciality is assessing the carbon balance and different environments and different land use.

Joel Houle Interesting. Michael, can you tell us a little bit about your work with forest insects?

Michael Stastny Yes, I'm a forest insect ecologist with Natural Resources Canada, with the Canadian Forest Service. And I work fairly broadly on ecological interactions that involve insect pests found in forest trees, including some invasive pests. And a lot of it is in the context of climate change and how we understand how the insects will behave under novel climate conditions.

Barb Ustina Very interesting. Now, before we do a deep dive into the research you're working on together, I just want to get a sense — just get the spruce budworm question out of the way. For people who aren't familiar with spruce budworm — what is it, and why is so much attention spent monitoring spruce budworm?

Michael Stastny Sure, spruce budworm is a native moth that lives in the forest and every three or four decades it has what we call an outbreak where its population basically explodes in huge numbers. And this is a completely natural phenomenon that we can even trace back in the history. And when that happens, you have caterpillars, the larvae of this moth, that basically consume the needles of fir and fruit trees. And it can really decimate the forest and create some conditions that basically kill the trees, eventually.

Barb Ustina Can you give us an idea of how much damage they're capable of causing and what stage we are at in the outbreak currently?

Michael Stastny Right now, in Atlantic Canada at least, the damage is actually quite minor. But the outbreak has been going on for about a decade — more than a decade actually in Quebec. It started on the north shore and then it switched over to the south shore of the St. Lawrence. Something like more than 7-million hectares affected. It's a very large scale — what we call a disturbance — that can have a major impact on not only how the trees grow and how the forest functions, but also trickles down to things like jobs in the forestry sector and so on. And that's why spruce budworm outbreaks tend to really get a lot of attention when they occur every few decades.

Joel Houle So, Michael, what part of your work made you think that you needed to reach out and get help? Not help, but maybe it was an opportunity to collaborate with someone from another government department.

Michael Stastny Yeah, it actually started quite organically. An area of research that hasn't been explored all that much when it comes to spruce budworm is how the impacts of feeding on the trees trickle down to the whole ecosystem. That's something that's been overlooked because it started with people worried much more about studying the populations of the budworm: how it impacts trees, what happens to the trees after they get damaged, but not really the broader picture. And I started a project with another colleague of mine at at CFS, Erik Emilson, that basically deals with the broader ecosystem effects. And it just turned out that another collaborator of mine at the University of New Brunswick, who knew of Louis-Pierre and his expertise in soil, got the two of us connected.

Barb Ustina So can you give me a sense of what kind of research you're doing and how you're collaborating together and how that sort of advances your knowledge or presumes to advance the knowledge of that spruce budworm?

Michael Stastny We have in the Gaspé Region of Quebec a series of sites that are actually forest watershed for entire drainage systems of forest streams, where we're following a whole bunch of things that occur during an outbreak, including how the trees are losing their foliage when the larvae are feeding on them. What happens to the streams and the water quality in the streams. What happens to their body conditions in the forest and cascading down all to fish communities. And things we they see down in the streets and even bird communities. And we have replicated the experiment over 12 different sites. And those experimental conditions basically lend themselves to asking additional questions, and therefore, we got the expertise of Louie-Pierre involved, because we're interested in what happens to the soil under the trees that are experiencing this feeding by the budworm.

Barb Ustina Now, you mentioned 12 different sites and raising additional questions. What were some of those additional questions that came up that you're trying to explore now?

Michael Stastny I think Louis-Pierre can probably comment on that even more so, but we became interested in basically asking what happens to carbon that's in the soil when you have this influx of those damaged needles falling onto the forest floor. The caterpillars excreting, their poop, basically. and what happens when you're starting to turn out the canopy as a result of this feeding, which means that there's more light penetrating through the canopy, through the branches of the trees onto the forest floor. And that in turn warms up the soil and then creates different abiotic conditions. And we became interested in how that affects the whole cycling of carbon in the soil and what happens to the communities of organisms in the soil that participate in those processes.

Joel Houle So how far along are you in your research? Have you come to any conclusions at this point or are you still trying to analyze the data on your findings?

Michael Stastny We're still fairly early on. We've done a couple of years of fieldwork. Well, on this specific project, I guess it's really just one year of fieldwork. We're heading into the second year. And a lot of these processes take a little while to show up in how we measure the ecosystem. So we're hoping that we will continue this project for a bit longer. We have a field season and then one more after that. But it's possible that some of those effects might not really show up until five or maybe even 10 years later. And that's just how the ecosystem processes and soil often operate. But in the meantime, we're basically measuring a lot of different things, so that we can both establish initial conditions, basically baseline data, that describes the ecosystem and how over time those conditions change in response to the spruce budworm feeding. In half of our sites, we prevent their feeding through insecticides, treatments that are part of landscape management programs in Quebec and Atlantic Canada and so on.

Barb Ustina Louis-Pierre, I'd like to hear from you, the research that you're doing in the field, as well as how it all connects with what Michael is doing in the field.

Louis-Pierre Comeau Yeah, well, coming back to the previous question of where are we in the project when it comes to soil carbon sequestration, normally, long-term studies are needed. So there, we would be at the beginning, because to be able to assess if an ecosystem is losing soil carbon or gaining soil carbon, normally that takes between five and 10 years of measurement and monitoring. But it's not only about the total soil carbon change that is important. In the soil there's a different pool of organic matter and carbon. Some of those are turning around really quickly and other ones are more stable with slow change. So my involvement in that project is partly or mainly to assess the balance of soil carbon by looking at the different pools of organic matters and their turnover rate, which are all affected by the spruce budworm and control of the spruce budworm.

Barb Ustina In terms of carbon in the soil then, carbon is really important for the health of soil overall. And I would think that spruce budworm populations are contributing more carbon to the soil as well, you know, as the pine needles fall to the forest floor. But is that the case? Is more carbon always better?

Louis-Pierre Comeau In the short term, when the disease is high and there are a lot of the needles falling down on the soil, we would expect and I believe we are starting to get a slight increase in carbon at the beginning. But we have to see what happens in the long run because the forests are dying. It is not healthy for forests or trees that are sick to increase the amount of carbon in the soil in the short run. What is important is to see comparisons over the long term between healthy and a non-healthy forests.  

Joel Houle Michael, if you guys establish some sort of link between a spruce budworm outbreak and an impact of carbon on climate change, what can we do with that information? How does that change the way that we approach monitoring spruce budworm and dealing with the outbreaks?

Michael Stastny That's a great question and not an easy one to answer because there are so many variables and so many factors that are considered in how we manage forests. So we can make recommendations based on our results to shift management in a certain direction. But there are always a lot of other competing variables at play. For example, there may be jobs in the forestry sector at stake, there may be reasons to control spruce budworm outbreaks through insecticides, but in some cases, instead of that, they can decide to go ahead with harvesting, basically cut down the trees before the impact really occurred. And so it's a difficult balancing act between these different interests and different ways of managing the forest. I think the bottom line with products like this is really understanding the system better. So we have more information and so we can make our decision with as much knowledge as possible and as much foresight, especially when we're facing challenges like climate change — that in itself will carry a lot of uncertainty for us. And how forest pests are behaving and how they're affecting the trees, but also how the trees are responding and then in turn, how things like nutrients, the nutrient cycling response to those factors.

Louis-Pierre Comeau And also, it's important that at the national level, when we do the greenhouse gas emissions accounting, we produce emission factors for different management practices. If our management practices produce more greenhouse gas than we reported, then the national inventories need to report the total. So for all the potential management of the spruce budworm, emission factors on that are needed too.

Barb Ustina I just want to get back to the research itself for a brief moment. I'd like to see if you can take me through a typical day in the field — what it looks like, how many people are on your team and what kind of work they're doing.

Michael Stastny Well, I'll give you a little bit of an idea. We have quite a few people that rotate through during the fieldwork, partially because we have four different collaborators coming from different levels of expertise. But basically, the way a typical day unfolds is we have crews going to the site through these watersheds, these experimental watersheds where we have spruce and fir forests and some populations of spruce budworm. And some of the things we're doing is, we're setting up what we call litter fall traps. Basically, they look kind of like a funnel made of mesh or screen that catch whatever is falling from the canopy above, which in the case of a spruce budworm outbreak means a lot of damaged needles and a lot of insect poop. And that's collecting in these collection devices and these litter fall traps so that we can quantify how much the soil is receiving from the canopy above. Then we have other team members that will be checking and data loggers that are recording soil temperatures. We have a set of people that are in Louis-Pierre's team that are extracting soil cores. And then at least once during a field season, we also have a crew that's reaching up into the canopy with really long pruners cutting down some of the branches of the canopy, so that we can sample how much defoliation is happening, how much foliage the canopy is starting to lose as a result of spruce budworm feeding. And so there's a lot of samples that make it back into the lab, and we start processing them and quantifying, getting the data from them somewhere that I think is still going on right now. Some of the samples are still in the freezer, and we can save them for later.

Barb Ustina So it sounds like it's a pretty labour-intensive process.

Michael Stastny Yeah. It really can be. It requires a dedicated team of people that are enthusiastic and not worried about getting dirty or getting sweaty or scared of bugs in the forest. So yeah, it can be a really cool team-building exercise.

Joel Houle Louis-Pierre, do you have any interesting stories about working with Michael in the field?

Louis-Pierre Comeau Oh, we have a lot of anecdotal and interesting stories! But what my team and I like is working with Michael at lunch time when we are sharing cheese and food with all the students and all the crew.

Joel Houle You're sharing cheese!

Louis-Pierre Comeau Oh, we do. Yeah.

Barb Ustina That sounds pretty exotic!

Joel Houle Can you elaborate on that Michael

Michael Stastny Yes, It started out actually as an initiative of our collaborator from the University of New Brunswick — who I think just recognizing that we're in Quebec, a region of Canada known for excellent cheese and charcuterie — decided that we should just all make little spreads of different cheeses and cold cuts and open up the tailgate of the truck. Then we spread it out there with a cutting board and everybody pitches in and gets to sample all kinds of really nice cheeses from the region. We’ve been doing that, and it's really fun and completely voluntary. So not everyone needs to partake, but it's been really fun.

Joel Houle So what you're saying right now is that for years scientists and researchers have told me that they're roughing it out in the field. But really, all of this is catered.

Michael Stastny Yeah, exactly. It’s the reward for really hard work.

Joel Houle Well, I'm sure it's well deserved. That's awesome.

Barb Ustina Oh, yeah. You need to have a few perks along the way for the people doing all the heavy lifting in the field for sure.

Joel Houle That's amazing. Thank you, guys for agreeing to talk to us today.

Barb Ustina Excellent. Thanks so much.

Joel Houle Michael and Louis-Pierre are doing some really fascinating research. So if you want to learn more about spruce budworm or soil carbon, check out the links in the episode description. One of the links provided is the episode that Barb and I talked about in the introduction with Rob Johns called'Slowing Down the Spruce Budworm. It's a great listen if you want to learn more about what we're doing here at NRCan to prevent spruce budworm outbreaks.

Joel Houle If you like this episode. Please subscribe. You can also leave a review or share this episode. If you share it over Twitter, make sure to tag me and also follow me at @JoelScience. All one word. Barb, you're on Twitter now, right?

Barb Ustina Indeed. I believe you're the first person to follow me is that right?

Joel Houle I think so, and it was quite the honor.

Barb Ustina I appreciate it! Anyway, you can find me at @SimplyScienceB. That's the letter B, and I just set up the account. And last time I checked, I think I had all of about 13 followers. So jump in, give me a follow and I'll follow you back. And a friendly reminder to everyone listening right now that Simply Science also has a website and a YouTube channel that you should check out. We have in-depth articles, truly spectacular photos and interesting videos that showcase the science we do at Natural Resources Canada. And you can find those links in the episode description as well.

Joel Houle Well, thank you, everyone, for listening. And we'll see you next episode.

Barb Ustina See you. Bye.