[00:00:00] Jordan Heath-Rawlings: It’s the first week of July, prime summertime, and wherever you were last outside, either in the park or your backyard or a cottage or a cabin or on a hike. Did you see any bare trees, trees that looked like it was the middle of winter? If the answer is yes, I’m going to go ahead and guess that you live in Southern Ontario or maybe Quebec. What you are looking at is a tree that has been attacked by what has most often been known as gypsy moths. And if it was a true outbreak, as there has been each of the past two years, and you’re likely looking at a tree or trees with basically no leaves left. We are used to seeing outbreaks of this invasive species every decade or more, but, and you might guess where this is going, all of a sudden they’ve come in back to back years and they’ve been much larger than in the past. So why now? [00:01:00] What’s driving this explosion and will it subside? How did those moths get here anyway? And what’s being done to control their spreads? And most practically, if you happen to notice the signs in your own backyard or favourite park for forest, what can you do to help the tree survive? What can you do to help the tree deal with it?
I’m Jordan Heath-Rawlings. This is The Big Story. David Dutkiewicz is the entomology technician at the Invasive Species Center. Hey David.
David Dutkiewicz: Hello.
Jordan Heath-Rawlings: Can you start just for the folks like me, who haven’t really thought about this problem, uh, until it reached a critical mass, I guess, w what are these moths that we’re talking about today?
David Dutkiewicz: Well, uh, they are a moth that has been in Ontario for a number of years now, almost 40 years now, however, [00:02:00] a lot of people don’t really recognize them or see them too often until they get to these larger outbreak status. We have had about three or four, um, sort of larger outbreaks since 1985, uh, 1991, as well as in 2002, they were all outbreaks over, um, a hundred thousand hectares of defoliation. To put some of that into perspective, uh, one hectare is equal to about the same size as a soccer field. So that’s a large area, uh, that has been defoliated by these, uh, gypsy moth. The species, it’s a type of lepidoptera, it’s a type of moth and butterfly. And this moth has come over from Europe, was brought over by a French scientist and he was basically trying to mate our native, uh, silkworms species, uh, with this gypsy moth in order to try and create a [00:03:00] new species that, uh, can produce silk.
So that’s really how the moth got here and why it became a problem is because that scientist, uh, the moth got away from him and started, uh, many issues in the Massachusetts area. And it slowly expanded from there. Um, this moth is about a, uh, inch in length. The females are very white. Uh, you can, uh, basically see them pretty clear on the trees. Uh, they actually don’t fly anywhere. So it’s surprising that they can get to large numbers, but, uh, it’s taken them 150 years to move from Massachusetts to Ontario. So I guess they do move a lot. Uh, the females will lay lots of eggs and that’s their only job is to lay eggs. Uh, and then the eggs hatch and, and they’re so great at multiplying because they can eat almost 250 different species of trees and shrubs. [00:04:00] So they’re not picky eaters.
Jordan Heath-Rawlings: What do the caterpillars look like?
David Dutkiewicz: Uh, well, the caterpillars, uh, can be about five to six centimeters long when they’re in the later stages. They are very fuzzy. That fuzziness helps them to disperse. They tend to be a very mottled, uh, head capsule. So it’s more like a black and yellowish brown color, and it moves into this nice black and white striping on the body. But the key features that you have to notice with the, um, caterpillars is they have a series of two pairs of dots along their back. There’s, um, five pairs of blue dots and six pairs of red dots along their back. And so they can be very distinguished through that ID feature.
Jordan Heath-Rawlings: And in general, where in Canada are they now? How widely have they spread?
David Dutkiewicz: Almost all of Southern Ontario. So you can find them anywhere from Windsor to, uh, [00:05:00] Brockville, to Sioux St. Marie, even up to North Bay, they have a population in Quebec as well, but it follows roughly the Oak area in Ontario and Quebec.
Jordan Heath-Rawlings: You mentioned that they eat a ton of different varieties of trees and plants. Is Oak their favourite? What else do they go for?
David Dutkiewicz: Yes. So Oak is their absolute favourite and what they’re most commonly found on. However, um, they will branch out to other different types of trees, uh, when the Oak is all gone. Um, in lower populations, you really don’t see them impacting, uh, other trees all that much. But when they’re in high populations, like they have been over the past, uh, two years, they’ll start to go after not only your oaks, but they’ll go after your maples, your birches, your aspens. One of the few species that will go between deciduous and coniferous trees. And they’ll actually go [00:06:00] after, um, you know, white pine populations or even, uh, Colorado blue spruce and other different types of spruces and things.
Jordan Heath-Rawlings: So you mentioned, uh, that they can defoliate areas of forest. What does that look like? And, and how is it different from what other species might do?
David Dutkiewicz: I guess the best way to say what defoliation looks like is it looks like winter.
Jordan Heath-Rawlings: Hmm.
David Dutkiewicz: So the leaves will flush out and the caterpillars just come and eat every leaf that they can possibly find. So we’re finding some trees have been a hundred percent defoliated, that means there’s not a shred of leaf left on it. So it looks like a winter time, which is very misleading for a lot of people because you go out to a forest and you expect these luscious green forest. Uh, floor of the forest, there’s all these beautiful plants that are starting to pop up, [00:07:00] but then you look up and there’s just sky. So a lot of people are concerned about that because you know, it looks like winter time and we just come out of winter time. It’s supposed to be summer, or you’re supposed to have shade. You’re supposed to have leaves on your tree, but yet these trees look very bare and barren.
Jordan Heath-Rawlings: Aside from the aesthetics of that, uh, is that bad for the tree? Do the leaves grow back, is the tree harmed? Like I’m trying to get, I guess what I’m trying to get a sense of is, cause we’ve heard a lot of chatter about how many, uh, of these moths are in Ontario right now. And I’m trying to get a sense of, you know, what the actual level of impact would be beyond like. They’re super annoying.
David Dutkiewicz: So I guess the biggest problem with gypsy moth is the fact that they’re, yes they’re super annoying, but they’re more like a gateway to something worse.
Jordan Heath-Rawlings: Explain them.
David Dutkiewicz: Repeated defoliation of trees, um, actually, when a tree gets defoliated for one to three years, the [00:08:00] tree can handle it. Most deciduous trees can handle a bit of defoliation. They’ll have a reflush, uh, later in the summer. So the trees are already starting to, uh, draw those sugars back up from the roots and to produce a new set of leaves. These leaves are going to be smaller, uh, they won’t be as large. They won’t photosynthesize as effectively, but they’ll still be a second leaf flush through, into August. But the problem is, is that they’re depleting their sugar storage. So. They’re kind of weakening themselves. So repeated defoliation from gypsy moth can stress the trees out, like immensely stress the trees out.
So after about three to five years of heavy defoliation, these trees are really stressed and they’re more susceptible to other types of common diseases and things like that. So common tree diseases and root rots, their defenses are [00:09:00] down. So. They’re basically susceptible to, uh, different funguses and stuff like that, that they would normally have no problem fighting against, but their immune system is just so depleted. Their sugar systems are just so depleted that gypsy moth can lead to other infections, killing the trees.
Jordan Heath-Rawlings: You mentioned that we’ve had sort of a series of outbreaks in the past. Are we having one right now? And you know, how long has it been since the last one?
David Dutkiewicz: Uh, so the last, uh, real outbreak was in 2002. There was approximately 150,000 hectares of defoliation. You know, that’s the size of say, for example, just the actual city of Toronto, but in 2020, we actually had the largest outbreak of a gypsy moth ever in Ontario. So we had basically 570,000 hectares of defoliation, which is pretty much the [00:10:00] size of PEI across Ontario. So that is a huge area of defoliation. And this year we’re also looking at those types of numbers. I won’t have the actual data for you until the Ministry of Natural Resources finishes their forest inspections. But, um, just anecdotally, we are seeing those types of numbers again.
Jordan Heath-Rawlings: I’ve done enough, uh, episodes about stories like this now to kind of guess that there’s probably going to be a discussion of climate change in here, but maybe not. Um, so why two outbreaks two years in a row when we hadn’t seen one for 20 years previously?
David Dutkiewicz: Um, you know, I wish I had a crystal ball for that. Um, it’s more of a combination of multiple reasons. So there’s no one specific reason why these gypsy moth has exploded over the last couple of years. You know, climate change does have an impact. Um, there’s a certain type of [00:11:00] fungus that in the springtime will affect the caterpillars and the fungus hasn’t had proper growing conditions in order for it to really get out there and kill the gypsy moth populations. Cause it needs a very, very wet, very rainy, um, spring season. And we really haven’t had those wet seasons. You know, get them more in bursts, but we have more of a drier spring this year. I mean, it was beautiful. It was great to get out, but a lot of that rain helps those types of funguses really knocked back the gypsy moth populations.
Jordan Heath-Rawlings: And what about temperatures? I know we had a warm winter this year and last year. Does that have any impact on them?
David Dutkiewicz: Oh yes, of course. Low temperatures, not a lot of snowfall, all that has a big effect. The caterpillars aren’t getting killed by those -20 degree days, you know, over -20, -25. We’re not having those types of temperatures sustained [00:12:00] over multiple weeks anymore.
Jordan Heath-Rawlings: In general, before we moved back to, uh, the moths, as someone who works in invasive species, does that have an impact in multiple species that you’re watching? Uh, does it, does it change the game?
David Dutkiewicz: Uh, yes. It allows for greater migration of north and south moving insects.
Jordan Heath-Rawlings: Right.
David Dutkiewicz: So a lot of east and west moving are moved a lot by human trade and moving back and forth. But north and south, um, you know, insects coming from, um, not only Southern Ontario, but like throughout the states are allowed to move, creeping slowly more into Canada. That is, uh, an impact that, um, warming temperatures or climate change does have on invasive species for sure.
Jordan Heath-Rawlings: What can be done to help control these populations. And I asked that both in the sense of like, what can cities and governments do if they’re interested in stopping [00:13:00] this at scale, but also just like for a listener, what can you do if they’re all over your backyard, trees and eating everything?
David Dutkiewicz: Um, well, for that I always tell people to take a multifaceted approach. Different life stages require different management treatments. For large scales, like cities or, you know, parks and things like that, in order to protect parks and their canopies, a lot of people will do aerial sprays of the bio pesticide, uh, BTK. They’ll do the aerial sprays in May time in order to protect the trees, and that’s when the caterpillars are out. Uh, this particular bio pesticide has to be ingested by the caterpillars. Um, so it only can be done, you know, during their early stages, uh, in order to affect them later in their later stages.
But hand-picking and burlap trapping is really all you can do towards the later stages. So, [00:14:00] um, for cities, they only have that one stage in order to go after them at a large scale. But, uh, for homeowners, they can go after them sort of while they’re caterpillars with their burlap banding traps to pick them off of the tree, or they can also pick them off when they’re pupa or adults. And, uh, they can also do egg mass scraping, which is just when the, uh, homeowner just goes around and scrapes the egg masses off of their trees, the ones that they can reach.
Jordan Heath-Rawlings: Maybe explain if you can, um, I get the handpicking. It sounds gross, but I understand it. Um, How do you do a burlap, a trap on a tree?
David Dutkiewicz: Basically what you do is you go to any hardware store and get a roll of burlap. Usually you can find them, uh, for covering Cedar trees and things like that. Uh, but what you would do is you would, uh, wrap the burlap band around the tree, just about chest height, [00:15:00] and you would tie a cord around the middle of that burlap and allow it to sort of drape over and allow the gypsy moth at place to be protected, basically. Um, because once they start defoliating, they don’t like the sun very much. And so they’ll hide during the day. They’re actually nocturnal feeders, at nighttime you can hear them crunching away on the leaves and things like that. So they’ll try and come down during the day and they’ll hide underneath that burlap. And the adults will do that as well. And so what as a homeowner you would do is you would go out to those burlap bands, lift up the burlap and just sort of pick off all the caterpillars that you can find, uh, or adults that you can find. I’ve heard reports of some people, uh, doing those types of banding and just, you know, vacuuming them up with a shop vac, uh, works great too.
Jordan Heath-Rawlings: What do you think happens next. And I’m not asking you to predict, you know, their population or the next [00:16:00] outbreak or whatever, but if this is kind of becoming something that we’re going to deal with on, on an annual or semi-annual basis, and the amount of land they’re covering is getting worse, um, Is this a problem that could metastasize on us, I guess? And do we need to be doing something on a bigger scale?
David Dutkiewicz: That is a interesting question because we, yes, we could do this on a larger scale in order to, uh, knock back the population. However, there are natural occurring sort of checks, I guess you would say, for the species. And we are seeing signs starting to show up in the population. So, you know, maybe next year the NPV virus will go through the population and will actually knock it back, so it’s only, you know, a couple thousand hectares of defoliation next year. Or it could be in two years from now. You know, we don’t really know per [00:17:00] se in order to predict when the population will crash. But in historically what we’ve seen is the population has grown to a peak and it’s just absolutely crashed like down to where it’s gone from 300,000 hectares all the way down to, you know, under 10,000 hectares in a single growing season. And that’s just because of, you know, higher predation rate or higher infection rate, uh, from either the virus or the fungus.
More or less, what you want to do for management side of things is you want to, um, have those in place that you know that there might be a higher gypsy moth yield and you can do certain things in order to sort of predict a couple of months in advance, but you’re never going to be able to predict, uh, years in advance.
Jordan Heath-Rawlings: So in the meantime, I guess, uh, homeowners just keep an eye on your trees and scrape off the pupa and, uh, and hope that there’s no [00:18:00] outbreak next year.
David Dutkiewicz: Yes. Uh, yes, that is the big hope. Um, like I said, there is hope though. Um, Cause one of the things, uh, with the virus, as many of us know now that viruses spread in larger populations really quickly. Now that we are actually starting to see some of the virus, it does give us as scientists hope that the virus will take a hold.
Jordan Heath-Rawlings: David, thank you so much for explaining this to me. It’s fascinating to learn so much about this creature.
David Dutkiewicz: It is definitely an interesting creature for sure. Um, so I’m glad you guys were able to reach out.
Jordan Heath-Rawlings: David Dutkiewicz of the Invasive Species Center. That was The Big Story, for more head to thebigstorypodcast.ca. Find us on Twitter at @TheBigStoryFPN, email us anytime email@example.com, and go to your favourite podcast player or your second or your third of your fourth favourite podcast player. Search for us, follow us, [00:19:00] subscribe, whatever they tell you to do. And if they let you leave a review, please write one.
Thanks for listening. I’m Jordan Heath-Rawlings. We’ll talk tomorrow.
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