30 Steve Frank – Healthy Trees, Healthy Pollinators


Speaker 1: From the Oregon State University Extension Service, this is Pollination, a podcast that tells the stories of researchers, land managers, and concerned citizens making bold strides to improve the health of pollinators. I'm your host, Dr. Adoni Melopoulos, assistant professor in pollinator health in the Department of Horticulture. If you've listened to past episodes of Pollination, you'll know we are pretty pushy about trees here. We love trees and we think they are an overlooked resource for pollinators. And that's why I was so excited to learn that Dr. Steve Frank, who's an associate professor of entomology at North Carolina State University, was spending the winter here in Oregon.

This gave me a great opportunity to sit down with Dr. Frank and learn more about his research. He sees urban street trees as providing multiple services back to the public ecosystem services. So things like providing habitat for pollinators, sequestering carbon, but also cooling the city down. If you think about all that concrete out there, it gets the city pretty warm and that can have a negative effect on pollinators. The other thing we cover in this episode is the tricky business of keeping trees alive. As you know, there's a number of invasive pests that are going across the U.S. They're taking down these beautiful boulevards of trees. And this kind of getting at this question of how do we keep those trees in place without having negative effects on pollinators when we're using things like pesticides? So this is a really timely episode, thinking about trees, keeping them healthy, and providing the benefits back to pollinators and to people who live in cities. I'm really excited. We've got a boat full of coffee and I'm right across from Steve Frank. Welcome to Oregon. Welcome to Pollination.

Speaker 2: Thank you very much. It's my pleasure.

Speaker 1: You know, we've talked about urbanization on the show a couple of times. David Loewenstein on a past episode, even last week we were talking with Al Shea about landscaping. And it really seems like a bit of a mixed bag when it comes to native and managed bees. People have commented and there have been all these studies that show like in an urban area this huge floral diversity and this kind of promise that it might be a kind of haven for native bees. But then there are these questions are we planting the right plants and all that? But then there's also the pest management aspect as well that some of these plants are going to require pest management.

Can you help us untangle these issues? What factors do we need to think about when it comes to considering whether urbanization is a good thing for native bees or a bad thing? Where do you stand on the urbanization issue?

Speaker 2: I don't think, I mean urbanization is going to happen and I don't think it has to be either entirely, it doesn't have to be entirely bad. It probably won't be entirely good. You know, habitat is a big aspect of this as people have probably mentioned on the show before, and that involves having flowers but also places for bees to nest. You know, most bees nest either in the ground or in stems or things like that.

And so that has to be available also. You know, the plant, the flower diversity can be much higher in urban areas because people are buying great numbers of plants and putting them in and a lot of them are exotic and some people don't like that either. But I think having flowers is good. You know, having a diverse array of flowers that bloom over the whole season is better.

I think, you know, the jury is still out on whether you should plant all natives or I think having some combination to extend the bloom time is probably the best approach at this point. Our work also shows that temperature, the urban heat island effect, affects bees and so, you know, this is the idea that cities are hotter than the surrounding rural areas because of all the pavement and things that absorb heat and radiate that heat into the environment. And we found that bees are sensitive to these changes in temperature and at higher temperatures where there's more impervious surface, you know, flowers help but certain bees just can't tolerate that temperature difference.

Speaker 1: So let me get this straight. You have this native bee community that sort of evolved without concrete and suddenly all this concrete comes in and these bees are still there. Some don't do well and some do well.

Speaker 2: Yeah, it seems, you know, bees and all creatures have, different species have different temperatures where they are comfortable and perform better. And so as the temperature creeps up due to climate change or due to urbanization, the urban heat island effect, some bees that can't tolerate that higher temperature are going to become less abundant or drop out of the community altogether.

And so by artificially increasing the temperature with a lot of impervious surfaces and maybe not having enough shade trees and things like this, you're excluding certain bees that can't tolerate those high temperatures.

Speaker 1: Wow, that's fascinating. And so I suppose when it comes to urban planning, there are coming back to these spaces that are not concrete. If you can kind of situate, there is a way to mitigate to some extent this effect. Or is there or is there just so much concrete out there really? It's not, it's something you just have to sort of anticipate.

Speaker 2: Well, yeah, there is. I mean, we also study the urban heat island effect on tree pests and, you know, the urban heat island effect is created when the sun hits concrete, that concrete absorbs heat and stores it and radiates it back into the environment.

Okay. So simply by shading that concrete, you know, if the sun isn't hitting the concrete, it's not going to absorb as much temperature. So, you know, if shading parking lots, shading roadways, shading your driveway, and things like that can have important effects and reduce the local temperature, the temperature can change in a city from block to block or even from house to house based on how much impervious surface there is and how much shade there is. And so people can you know, help their sort of local microhabitat just by shading their driveways, shading their house and things like that, which saves you energy to boot. So it's not all hopeless.

You can do things to help reduce that. But in a big sense, you know, cities are largely concrete and brick buildings and rooftops and things. So there's always going to be some higher temperature in cities.

Speaker 1: You know, when I think of trees here in Oregon, I think about shade trees and I think about shade trees just across the nation having a whole host of pest problems that seem to work against, you know, these shade trees can help, you know, mitigate these heat island effects. This overlaid problem of pest problems seems to work against it. And it really strikes me that one thing that's really been really interesting of work that you and your collaborators have done is really think about native bees in conjunction with these pest problems, maybe expand a little bit more about how you think about pest problems and pest problems and pollinators in an urban setting.

Speaker 2: Sure. How I think about pest problems is usually all the time.

Speaker 1: I walk around with my kids and I tell them about scale and sex and, you know, they can identify leaf miners and scales and probably get tired of it. But you know, it is a big issue that the same urban heat

Speaker 2: The island effect that is bad for bees is also good for some pests particularly scale and sex, which are what we've found to be the most affected by temperature. And so you have, again like you said, trees that are supposed to be shading the sidewalk and performing other services like sequestering carbon and looking nice even that is heavily infested with scale and sex, which makes them look ugly and not sequester carbon that we've found.

So it is a problem and spraying them within sex size is not the answer because then that's bad for bees and people and dogs and chipmunks and most municipalities don't have the money to spray every tree anyway. So I mean, we're hoping to find, you know, to determine in different settings which trees perform the, you know, some trees can do well in a hot environment and not have many pests, we assume. So if we can, if we can refine the planting plans, especially by landscape architects, if they specify red maples in every single parking lot of every single plan, well, that's not the best tree. And we actually have thresholds now where if a tree is surrounded by more than 30%, if a red maple, I should specify is surrounded by more than 30% pervious surface, you shouldn't plant it there. It's going to turn out as a poor tree.

So things like this can help us actually from the design stage create more sustainable landscapes by putting the right tree in the right place so that it performs the services that we want.

Speaker 1: So I guess, you know, one way we often think about it is at the tail point, there's been a bad selection, it needs insecticide to keep the pest under control. But what you're saying is that much of this could be circumvented, you can get these benefits and not have to deal with the pest problems if you just think about plant selection at the front end.

Speaker 2: Yeah, yeah, I think that's true. The more we learn about plant selection and the same with pollinators, the more plants are good for pollinators and certain ones probably are sort of indifferent for pollinators. You know, red maples, at least back east are the first trees to bloom and provide an important flowering resource for bees just as they come out of hibernation and are hungry.

And so if those trees aren't blooming, or their phenology is screwed up because it's hot or they're drought-stressed, then that interaction that the bees rely on coming out of hibernation and finding those red maples in flower the way they're supposed to be could be disrupted.

Speaker 1: You know, we were talking earlier, and I thought this was a really great example. It's a slight tangent, we were talking about azalea lace bug. It's a real problem here in the Pacific Northwest, everybody is having to deal with it and you know, extend it on to wild plants like salal. Real problem, but you said you kind of mentioned something about landscape complexity, where one might think about azaleas, first thing, you may not plant azaleas because of the problems, but there is a kind of, there might even be a contextual kind of way of thinking about azaleas in the landscape, not just doing the whole. Could you expand a little bit on that idea? That was great. Sure.

Speaker 2: And in our lab, we think about, we say habitat complexity or vegetation complexity, which is just the idea that you have a lot of different kinds and sizes and shapes of plants in your landscape. And in that way, it looks more like a forest. You've got overstory trees, oaks, and maples. You might have understory trees like dogwoods or red buds and a shrub layer and you can have grass or some kind of land cover or ground cover under that.

But having all those components, the way you would see in a forest and in a forest that azaleas would grow in, they're understory shade plants, even in their native range. And a lot of times we put them in full sun with no overstory trees and things that cause them stress. A stressed plant usually has more pests and is more pests susceptible than a healthy thriving plant. The other issue is that there are more complex landscapes, the other good thing that they create is a habitat for predators and parasitoid wasps and things like that that also help keep pests under control. And so by isolating plants in sort of barren, hot landscapes, you're causing the plants stress that makes them more susceptible to pests and you're making it impossible for the predators and parasitoids to live there that would help reduce the pests. And so it really is a double benefit for the pests because they have a stressed plant and no predators. And so by increasing the diversity of plants in your landscape and the diversity of structures of those plants in your landscape, one, I think it's more beautiful. It looks more like a forest.

For sure. But it also has a lot of benefits in terms of not just azalea lace bug pest control, but pest control for scale insects and aphids and other things. Because you have all those predators, those natural enemies that are helping reduce the pests, you're also with more kinds of plants more likely to have more things than pollinators. Oh, for sure. Just by chance, if you put in more kinds of plants, you're bound to have more kinds of bees.

Speaker 1: More diversity. You'll just be able to really kind of key into sort of different host preferences. Yeah. Yeah. You know, it's striking, you know, you go out and you buy this real expensive plant and you don't think forward to the maintenance. And maybe that brings up the issue that maybe people don't know, maybe the landscaper isn't familiar or maybe the homeowner also is not thinking or the person in charge of that land of those costs. Because I can just imagine that you buy this plant and then have all of this kind of continual maintenance costs, which the plants seem like a big cost upfront, but then you got all these other costs coming down the pipe.

What sets this up? People ought to be able to sort of work around this issue. More beautiful gardens, fewer problems, less costs, but yet we don't do that. What's your experience with this problem?

Speaker 2: Yeah, I think partly it starts with plant selection and once you select a plant, whether you put it in a place that it's happy or not, if you go to a big box store and look at the selection of plants, it's often not great. There's not a lot of different kinds of plants. In some specialized nurseries, you can find more things, but they're more expensive. And so You know, everybody's going to the same stores, and the landscapers are going to the same nurseries and getting the same kinds of plants. I see the same plants here. I live in Eugene right now I live in North Carolina. The landscapes look the same. CB – That's really crazy.

Speaker 1: AC – Yeah. And there's no way that the forests don't look the same. CB – Right. Right. AC – The forests look totally different. But the same landscape plants, the boxwoods and the Japanese hollies and the whole bit is the same. So anyways, they're not always planted in the correct place to reduce pests.

I think some of it is also just tradition. People like boxwoods, for instance. And over the years, boxwoods have accumulated so many pests, spider mites, and leaf miners. And now this box blight, which is a disease.

But we continue to plant them, even though they may have exceeded the number of pests they have now probably makes them not very sustainable and not a maintenance-free choice for sure. So I don't know if that answered your question.

Speaker 1: CB – No, it does. It does. AC – It went on for a while. And you do have, when you go to make choices, you don't have a lot of choices. And that kind of drives some of this homogeneity.

Speaker 2: CB – Yeah. And information about the choices too. I mean, people, you know, homeowners, they try and do the best they can. They want three yards to look nice. But it's not like there's a sign that says this plant is going to be covered in pests in three years.

Speaker 1: They don't know that if you plant the euonymus in three years, it's going to be covered with scales almost invariably. It looks nice. It's got shiny leaves. It's evergreen. Stick it in the ground. And, you know, and so they don't know in industrial or commercial plantings where you do have landscape architects and landscapers informed people making these decisions. Maybe sometimes we could do better because they have the information or should. So I think it's a combination of things.

Speaker 2: And the more widely available and mass-produced a plant is, the less expensive it is also. AC – Of course. Yes. CB – And so that's going to drive commercial plantings and homeowner plantings.

Speaker 1: AC – Yeah. That affordability issue. I mean, that is nothing to sneeze at.

Speaker 2: CB – No, really. AC – Landscaping isn't in commercial infrastructure. Landscaping is the last line item. After everything else gets taken care of, you put in the landscape with the leftover budget probably. And homeowners, you know, they don't want to go broke buying plants and sticking them in. So, yeah, it has to be affordable.

And we probably, everybody probably need more help selecting plants that would be hopefully good for pollinators and also not require a lot of maintenance in terms of pesticides and other things.

Speaker 1: AC – So let me just transition here on to, and we're going to, this is going to be a shorter episode. I think we're going to take a break in a minute and go straight to these questions we ask all our guests. But I just wanted to hear a little bit about the kind of work extension in North Carolina is doing to try and raise these issues. I mean, they seem, it seems on the East Coast, there's been a lot more work on pollinators, pest management, and extension than on the West Coast. And in many ways, I'm really looking for guidance from these ongoing efforts. What would have been some of the successful things that you've been able to get going in North Carolina?

Speaker 2: AC – Well, you know, my lab, thanks to a couple of really focused people, you know, we've started a website that has material for homeowners and other folks about native pollinators in particular. And, you know, we're doing some research to understand the effects of urbanization on native pollinators that feed into the extension program. We've got a couple of county agents that do a phenomenal job, just because they have the passion for it.

And they educate a lot of homeowners and landscapers and things. You know, so things like that, we sent out bee boxes. Yeah, a lot of people don't even know what native bees are. If you say bee, they think honey bee, maybe a carpenter bee that's digging into their deck or something, right?

But in North Carolina, we have 500 species of native bees. AC – Yeah. AC – Most people, and I didn't know much about them until a couple of years ago, when we started working with these, you know, that's the bee community, you know, not the honey bees, and, you know, important as they are. So we do a lot of outreach events for kids and for grown-ups and master gardeners and anybody who will listen just to let people know these bees exist and that, you know, ways to help them.

Speaker 1: AC – Well, I had the great pleasure of visiting the site and there are the really nice bulletins on, like, you know, how to set up cavity nesters and what you'll see inside them, really nice crisp publications that are really accessible to people who, as you say, this is their first introduction to bee biodiversity. AC – Right. AC – They may have thought there were only three bees in their state.

Speaker 2: AC – Yeah, and I think, you know, the, you know, the idea that there's some sort of bee crisis going on, I think the positive is that people are jazzed about bees. And until the next crisis comes along, we have people focused and we can educate them about bees. You know, you never know when the next thing's going to come up and people's attention will be diverted to whatever it is, hummingbirds or some other crazy thing.

But now we've got them focused on bees and so if we can try and educate them and get them to plant a few more flowers and a little more shade, now's our chance.

Speaker 1: AC – Awesome. That's great. Well, let's take a quick break and we'll come right back. Okay, well, we're back and I was really kind of holding myself back to ask you, but I'm going to ask you now about plant selection. So people probably dying to know, you know, what kind of plant should I plant? What's your answer to that? What are you kind of?

Speaker 2: AC – Yeah, my answer, there are lots of plant lists out there that list all kinds of herbaceous perennial plants often and annuals and things, but my answer is trees. And I think trees are generally overlooked as a pollinator resource. But if you think about where a lot of honey comes from, sourwood honey, that's a tree. As I said before, maple flowers, you know, a maple tree probably has more flowers than half an acre of some kind of perennial or annual. And trees are infrastructure. So they're there once you plant them.

They're there for a long time. Some of these community gardens and things can come and go based on one enthusiastic citizen who moves away and then the whole process collapses. I think if we can get more flowering trees in the landscape that are pollinator-friendly, it adds a level of stability to the resources that are available because the trees are there for 20 30, or 100 years. And some of these, the amount of flowers in the landscape changes with development patterns. Again, do you have a master gardener in your neighborhood who's really driving a community garden or something like that? That all comes and goes, but the trees are there.

Speaker 1: I love that. I remember my wife and I lived in Northern Canada and every little community had a tennis court. There was this fitness craze in the 70s, but that infrastructure was still there.

It had lived long past the craze. And I think about the same thing. When you get these trees in the ground, if they don't have pest problems, attitudes may change, but the tree's still there. That is a really great point. I love that point. Thanks. Right. Plant more trees. And they're overlooked.

It's just like here, I remember talking to people who do mason bee production and they really look for, when they're propagating, they're looking for an area with just a lot of maples.

Speaker 2: Yeah. Yeah. Maples and tulip poplars and sour woods and all these great trees that produce hundreds of thousands of flowers each are good for bees. Awesome.

Speaker 1: Okay. So here I got these questions. I know we're short on time, so I'm going to ask you these three questions. The first question is, is there a book that you want people to know about as influential to you or just like your favorite book, even though it's really geeky?

Speaker 2: No. You know, what I do, what I like to do is when I have a topic I want to write a blog about or read about or something. The first thing I do is go to Google Books and search for the old books because I like to see the old drawings, all these pen and ink drawings that people do and you realize that people learned all about these creatures 100 years ago or 200 years ago. And now sometimes people are relearning that stuff now. So I guess my answer is just to look for the oldest books I can find because I love the illustrations and I like to see how much people actually knew back then that maybe has even been lost.

Speaker 1: That is a great suggestion. We have had, there was this funny running little thread. We had numerous guests who were competing with old ABC and XYZs of honeybees, like 20s editions and 30s editions.

But I just came across this crazy study in Illinois in the 1890s of plant-pollinator interactions that was unparalleled. You may not even be able to pull that off today. It's amazing. Yeah, I know that work.

Speaker 2: Yeah, stuff like that. People had time to do more extensive surveys and a lot of real natural history that now, at least academics, find hard to get funding and time for.

Speaker 1: Okay, so you've got your pen down there for the old stuff. Go, dear listeners, look for the old stuff. Okay, that's first. Second, if you were on a desert island and there was a tool for doing your work that was indispensable, you really could not do without it. Or perhaps there's a tool that you're known for. People say, oh, that's the Steve Frank tool.

Speaker 2: What tool would that be? An Optimizer. A what? You never heard of such a thing. So this is, I mean, the brand we use if I'm allowed to say brands, is Optimizer. It's just an OPTI Visor. And it's just one of those Visitors you put on that has magnifying glasses in front of your eyes. So that everything you look at is magnified.

And so when I'm inspecting plants or looking at insects, rather than having a tiny hand lens that you're right up on and seeing one tiny thing at a time, you can scan a whole plant, and the whole thing is magnified and you feel like a superhero. When you take them off, they're the worst part. You take them off and you're disappointed in your original vision, right?

Because it's terrible. But I take an Optimizer everywhere I go. And I push them on nurserymen and landscapers and anybody trying to do IPM because it really makes it easier. And you see all this great stuff.

Speaker 1: You know, Remite, a conversation that we had earlier today, you were talking about like the, you know, how a lot of insecticide use or pesticide use could be reduced if people just identified the pest.

Speaker 2: I think that's true. I think a lot of insecticides are applied because there's a symptom on the plant that maybe a pest caused or maybe it didn't or maybe a pest caused it earlier in the year and isn't there anymore. And so using a tool, you know, some sort of magnification to actually check and see if the pest is there and what it is and whether the product you're thinking about will actually kill that pest would make a lot of difference.

Speaker 1: I like how your two questions sort of connect in some ways because the first, you like the old stuff because people would take the time to watch, and like you actually want people to take the time to watch.

Speaker 2: Yeah, I think that's true. Inspect a plant before you spray it.

Speaker 1: Well, as you can see, they're barking at the doors here at Pollinator Health. So we got one last question for you and I'll let you go. Do you have a favorite pollinator species? Is there some critter when it flies by you're like, that's cool.

Speaker 2: I think for me, well, I actually just thought of another one, but bumblebees generally, I think, you know, have sort of become a mascot for native bees as opposed to honeybees. There, you know, a lot of research has been done on them. They've been, we kind of have studied the effects of climate change on them.

So I would say honeybees just because it's the biggest thing people, I mean, bumblebees and not a particular species for me, but just as a group, people can see them. It's something you could do citizen science with people, I'm sure. And the public can actually, you know, they're cute and fuzzy. So I think those as sort of a mascot for native bees is good.

But you had a second thought. Oh, well, I just was in France and I learned about this exotic, they have this exotic wasp. It's called a yellow-legged hornet. And it's probably two inches long and it hunts honeybees. Really? And so it, I love that because it's awesome. I mean, it hunts honeybees, which is cool, but probably not good, right? So anyways, well, you know, everybody's got a lip. I like it. I like its awesomeness, but it's really damaging.

Speaker 1: All right. Well, we've got the, you've got two extremes, the teddy bear of the bees and the butcher of the bees as like, that's a really, like your extremes on the answers there. Thank you so much for, I know, and just briefly, what are you doing in Oregon? We're so excited to have you here.

Speaker 2: So, so my job is at North Carolina State University. I'm on sabbatical in Oregon and Eugene. And, you know, I'm getting around meeting people, learning more about the ecosystems out here, and generally enjoying myself.

Speaker 1: Well, we're so excited to have you here in Oregon. And thanks for taking a little bit of time out of your data for recording this episode. It's my pleasure. Thanks for having me.

Thanks so much for listening. Show notes with information discussed in each episode can be found at pollinationpodcast.orgonstate.edu. We'd also love to hear from you, and there are several ways to connect. For one, you can visit our website to post an episode-specific comment, suggest a future guest or topic, or ask a question that could be featured in a future episode. You can also email us at pollinationpodcast at organstate.edu. Finally, you can tweet questions or comments or join our Facebook or Instagram communities. Just look us up at OSU pollinator health. If you like the show, consider letting iTunes know by leaving us a review or rating.

It makes us more visible, which helps others discover pollination. See you next week.

Dr. Steve Frank is an entomologist who recognizes that urban trees provide a lot of services back to people living in cities. Trees also provide a lot resources to pollinating insects as well. Given the importance of trees to broad ecological systems, Dr. Frank looks for practical and innovative ways to preserving tree health. His lab also studies how the urban heat island effect increases insect pest abundance and damage on urban trees and the congruence between urban and global warming to determine if cities could serve as canaries in the coal mine of climate change to predict pest outbreaks in natural forests.

Listen in to learn about how urban environments affect pollinators, what homeowners and civil planners can do to improve them, and which plants and trees are best for the city.

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And be sure to leave us a Rating and Review!

“People can even help their own local micro-habitat by shading their driveway and their house and things like that, which saves you energy to boot.“ – Steve Frank

Show Notes:

  • How urbanization affects pollinators and their habitats
  • What you can do to help pollinators in your urban community
  • How cities can design their spaces to better suit their natural landscape and it’s pollinators
  • How Steve uses “habitat complexity” to better urban landscapes
  • Why stressed plants can produce many problems for pollinators
  • Steve’s recommendations on plants for pollinators at your home
  • How Steve finds his favorite books

“You have a master gardener in your neighborhood who’s really driving a community garden or something like that. That comes and goes, but the trees will still be there.“ – Steve Frank

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