Chalara fraxinea

Subscriber-only episode

Episode Summary (English):

 In this Saturday episode of Talking Trees, we examine the devastating impact of Chalara fraxinea (Hymenoscyphus fraxineus), the fungal pathogen behind ash dieback in Europe. We explore the spread, symptoms, and susceptibility factors affecting Fraxinus excelsior and other ash species, including findings from Ukraine, Poland, and Lithuania.

We discuss:

• How the ash dieback pathogen and emerald ash borer are compounding damage in Eastern Europe
• The potential role of bud burst timing in ash resistance, with earlier-bursting clones showing greater survival
• The presence of wood-inhabiting fungi, like Armillaria cepistipes, in weakened trees, and their possible role in secondary decline
• The importance of phenological and genetic traits in breeding programs for resilient ash populations

This episode highlights current scientific insights into ash decline and disease ecology, offering a hopeful look at strategies for future forest resilience.

Background information:

• Davydenko et al. 2022. Invasion of Emerald Ash Borer Agrilus planipennis and Ash Dieback Pathogen Hymenoscyphus fraxineus in Ukraine - A Concerted Action.pdf
• Przybylski et al. 2024. Spring's Signal_ Can Bud Burst Timing Enhance Resistance to Ash Dieback in Europe_.pdf
• Wood-inhabiting_fungi_in_stems_of_Fraxin.pdf

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Chapters

• 0:00 Introduction to Ash Dieback Crisis
• 1:37 Spring Phenology and Survival Rates
• 3:07 Armillaria Fungus in Lithuanian Trees
• 5:30 Promoting Genetic Diversity in Ash
• 8:25 Treatment Options and Management Strategies
• 10:15 Forest Health and Conservation Approaches
• 13:16 Practical Tips and Closing Thoughts

Transcript

Roger: 0:02

Talking Trees with Lillian Jad. Welcome to Talking Trees. Today we explore the recent studies on the impacts of Agrylus planipennis, emerald ash borer and Hymenocyphus fraxineus ash dieback on ash trees in Ukraine, highlighting their combined effects. We also discuss research on the timing of ash bud break in Europe and its connection to survival rates, as well as findings on wood decay fungi like Armillaria capistipes in Lithuania, shedding light on the biological and ecological factors influencing ash tree health in Europe. Let's dive in.

Jad: 0:45

Hey everyone, I'm so glad you could join us today as we take a look at some really interesting research on ash dieback.

Lilly: 0:51

Yeah, it's definitely a hot topic right now, and these new studies offer some pretty intriguing insights.

Jad: 0:57

You know we're all dealing with ash dieback out in the field and I think these papers could change how we approach things.

Lilly: 1:02

Yeah, for sure. They definitely highlight just how complex this issue is.

Jad: 1:08

So let's just get right into it. Can you kind of set the stage for us? How bad is ash dieback in Europe right now?

Lilly: 1:15

I know it's not good, but you know, in some areas we're looking at losing almost all our ash trees like up to 95% in some places and when you think about the ecological and economic impact it's pretty alarming.

Jad: 1:28

Yeah, that's a scary thought.

Lilly: 1:30

You know, the UK alone is projecting a 15 billion pound loss over the next century because of this.

Jad: 1:35

Wow, that's a massive hit and you know we still don't have that like silver bullet solution to this problem.

Lilly: 1:41

Exactly, and that's why research like the study from Poland is so important. They were looking at what's called spring phenology, so basically the timing of bud burst and how it relates to how susceptible a tree is to ash dieback.

Jad: 1:56

Okay, interesting. So they're looking at when those buds pop open in the spring.

Lilly: 1:59

Yeah, they observed 31 different ash clones in a seed orchard over three years. They were really meticulous about tracking. You know when each clone burst its buds and then how much defoliation it experienced from the dieback.

Jad: 2:11

Okay, so what did they find? Does the timing of bud burst actually correlate with survival rates for the trees?

Lilly: 2:18

It's amazing. Actually, the clones that burst their buds earlier in the spring had a significantly higher survival rate, sometimes as much as 20% higher, and they also had a lot less crown damage compared to the clones that burst their buds later.

Jad: 2:30

Wow, that's a pretty big difference. So for us out in the field, does this mean that we should be selecting and planting ash trees from lineages that we know bud out earlier? Could that give them a better chance?

Lilly: 2:41

You know, that's a really good question and the research seems to indicate that it could be a viable strategy. By focusing on those early bud burst varieties, we might be able to increase the resilience of our ash populations.

Jad: 2:53

but of course, more research is needed Right, of course, but it's a really interesting avenue to explore for sure. Now let's move over to Lithuania. This study focused on the role of wood-inhabiting fungi in declining ash stands.

Lilly: 3:07

Right, and they were specifically looking at a fungus called Armillaria sepestipix.

Jad: 3:12

Okay, and I've heard of Armillaria sepestipix. It's not usually considered to be a major threat to ash trees, is it?

Lilly: 3:17

Well, that's what makes this study so interesting. Typically it's considered a kind of weak pathogen, but in this study they found it in almost every single ash tree they sampled, whether the tree was healthy or declining or even dead.

Jad: 3:28

Hold on. That doesn't sound right. I mean, usually armillaria sepestipes goes after trees that are already weak and not healthy ones. So what's going on here?

Lilly: 3:36

That's the big question. This study found that active decay caused by armillaria sepestipes was present in a huge percentage of the trees. By Armillaria sepestipes was present in a huge percentage of the trees 80% of healthy trees, 98.5% of declining trees and 100% of the dead trees.

Jad: 3:52

Yeah, those are some pretty stark numbers, so it seems like an IS playing a significant role, maybe even being a primary pathogen in some cases.

Lilly: 3:59

That's what the evidence is suggesting. And to add another layer of intrigue to all this, the study also looked at the clonal structure of this fungus.

Jad: 4:06

Okay, what do you mean by clonal structure?

Lilly: 4:08

Well, they found these large genetically identical colonies called genets, spreading throughout the ash stands. It's like this giant underground network of this fungus, all connected and spreading for meters.

Jad: 4:18

So it's not just individual fungi, it's like these massive interconnected colonies.

Lilly: 4:22

Yeah, and some of these genets were at least 20 years old, meaning they were there long before the decline of the ash trees even started.

Jad: 4:28

So this fungus has been present in these stands potentially for decades, before the dieback became obvious.

Lilly: 4:34

Exactly, and it makes you wonder what triggered this shift in behavior. Did something change in the environment, maybe related to climate change or some other stressor that caused this fungus to switch from this relatively benign inhabitant to this more aggressive pathogen?

Jad: 4:49

It's almost like this common fungus that we thought we knew has suddenly revealed a whole new side to itself.

Lilly: 4:55

It definitely challenges our understanding of its role in all of this.

Jad: 4:58

It really makes you wonder what other factors might be at play here, things that we might have overlooked.

Lilly: 5:03

Yeah, it definitely raises some important questions and it highlights the need for more research and, you know, a more holistic approach to understanding this issue. It's not just about fighting a pathogen, it's about making the tree stronger and creating conditions that help it resist.

Jad: 5:17

That makes sense, and you know. Speaking of resistance, one thing that's come up a lot in discussions about ash dieback is the idea of genetic diversity. Right, Some ash trees just.

Lilly: 5:30

Oh, absolutely. Genetic diversity is one of our best tools in this fight. If we have a wide range of genes in the population, there's a much better chance that some of those trees will have the traits that help them survive the disease, or at least tolerate it better.

Jad: 5:44

So, as arborists, how can we actually promote that genetic diversity? You know, in the ash trees that we work with Well, there are a few things we can do.

Lilly: 5:53

First, when we're planting new ash trees, we should make sure we're getting them from a variety of sources, different provenances, not just relying on one single supplier.

Jad: 6:02

So mixing it up geographically basically.

Lilly: 6:04

Yeah, exactly, bringing in a wider range of genetic material, and we should also be encouraging natural regeneration whenever possible, letting those ash seedlings sprout and grow in areas where there are already ash trees. This lets nature do its thing, you know, selecting the individuals that are best suited to the local conditions.

Jad: 6:21

That makes sense, but isn't there a risk that those seedlings will inherit the susceptibility to the disease from their parents?

Lilly: 6:28

There's always that possibility. But even within a group of susceptible trees there's going to be variation. Some will be more resistant than others. By letting them regenerate naturally, we're giving nature a chance to pick out the ones that have a fighting chance.

Jad: 6:42

So it's about letting nature do its thing, but also kind of guiding it in the right direction.

Lilly: 6:47

Exactly. And that brings us to another really crucial factor the environment.

Jad: 6:51

Right, because it's not just about the genes, it's also about where those trees are growing and what conditions they're facing.

Lilly: 6:56

The environment plays a huge role in a tree's overall health and its ability to fight off disease. When a tree is stressed, it's way more vulnerable to infection, so we need to do what we can to make sure those trees are as healthy as possible.

Jad: 7:10

So things like making sure they have enough water, controlling competing vegetation and protecting them from other pests and damage.

Lilly: 7:17

All of that's important and as climate change continues to affect our forests, we need to be even more aware of these environmental stressors, like drought stress, for example, that can really weaken ash trees and make them more susceptible to the disease.

Jad: 7:29

So it's almost like we're not just planting trees, we're creating whole ecosystems that can support them.

Lilly: 7:34

I like that way of putting it.

Jad: 7:36

We've talked a lot about the challenges so far, but are there any reasons to be optimistic, any signs that we might be turning a corner in this fight?

Lilly: 7:44

You know, there's definitely no easy fix, but there are reasons to be hopeful. We're learning more about this disease all the time, and we are finding trees that show natural resistance, and we're developing new management strategies based on the latest science and I think one of the most encouraging things is that there's just so much more awareness about this issue now among arborists, landowners and the public. I agree that awareness is driving research, it's driving funding and it's driving the collective action that we need to protect these trees.

Jad: 8:14

OK, so we've talked about genetic diversity and managing the environment, but what about more direct control measures? Are there any treatments or techniques that can be used to actually combat the disease itself?

Lilly: 8:26

Unfortunately, there's no magic bullet cure for ash dieback. Once a tree is infected, there's no guaranteed way to get rid of the fungus. However, there is some promising research being done on things like fungicides, you know. Maybe we can find a way to protect trees from infection or slow down the disease.

Jad: 8:43

But it sounds like those are still a long way off.

Lilly: 8:45

Yeah, they're still in the early stages and there are challenges with effectiveness and cost and environmental impact.

Jad: 8:52

So no quick fix there. What about pruning or removing infected branches? Can that help?

Lilly: 8:57

That's a common strategy and it can definitely help to some extent. You know, getting rid of those infected branches reduces the number of fungal spores in the environment, which could slow down the spread. But it's important to remember that the fungus travels through the air, so pruning alone won't solve the problem.

Jad: 9:12

It seems like every approach has its limitations. So how do we choose the best course of action when we're out there dealing with ash dieback in the real world?

Lilly: 9:20

Well, it's not always easy and the best approach is going to depend on the specific situation, but I think the most important thing is to focus on prevention and early intervention. We need to be really observant, monitoring our ash trees for any signs of the disease, and we need to be really observant, monitoring our ash trees for any signs of the disease. And we need to be proactive, implementing strategies that can reduce the risk of infection and just keep those trees as healthy as possible.

Jad: 9:42

So it's all about being observant, informed and ready to act quickly.

Lilly: 9:45

Exactly and being realistic. You know, we may not be able to save every ash tree, but we can make informed decisions that give them the best chance of survival.

Jad: 9:55

This whole conversation has really highlighted just how complex this issue is, but it's also given me a renewed sense of hope and purpose. You know, as an arborist.

Lilly: 10:04

I feel the same way. It's a big challenge, but it's also an opportunity to use our knowledge and skills to really make a difference.

Jad: 10:09

And that's what it's all about. Right, Protecting our trees.

Lilly: 10:12

Absolutely.

Jad: 10:15

It's a privilege and a responsibility. Okay, so we've talked about genetic diversity, environmental management and the limitations of direct control measures, but let's zoom out a little bit. How does ash dieback fit into the bigger picture of forest health?

Lilly: 10:27

That's a great question, and it's one that we don't always think about enough. You know, ash dieback isn't an isolated incident. It's part of this larger pattern of emerging forest diseases that are popping up all over the world.

Jad: 10:39

So it's like a warning sign of a bigger problem.

Lilly: 10:41

Exactly, and it reminds us that we need to think beyond just one species or one disease. We need to be thinking about forest management in a more holistic and integrated way.

Jad: 10:51

So what does that look like in practice?

Lilly: 10:53

Well, it means promoting diversity on every level. You know, species diversity, genetic diversity and structural diversity. It means creating conditions that favor native species and make it harder for invasive pests and diseases to take hold. And it means addressing the root causes of forest decline, things like climate change and unsustainable land use practices.

Jad: 11:13

It sounds like a huge task.

Lilly: 11:15

It is, but it's absolutely essential if we want to ensure the long-term health of our forests.

Jad: 11:20

And to do that we need knowledge, collaboration and a willingness to adapt our practices based on the science.

Lilly: 11:25

Absolutely. We need to keep learning, keep sharing and keep working together to find solutions.

Jad: 11:32

You know, it's easy to get overwhelmed by all this. It's a really complex issue, but I think the main thing I'm taking away from this is that there's IS hope.

Lilly: 11:39

Yeah, I agree. It's not a hopeless situation. We're learning more all the time, and that knowledge is giving us the tools to develop new strategies.

Jad: 11:46

It's about shifting from reacting to the problem to being more proactive and adaptable.

Lilly: 11:51

Absolutely, and we have to remember that ash dieback isn't just a scientific problem, it's a human problem too. You know, these trees are important to people, to wildlife, to the whole ecosystem.

Jad: 12:03

So it's not just about saving individual trees, it's about protecting what those trees represent. You know their ecological and cultural value.

Lilly: 12:11

Exactly, and that might mean making some tough choices, like deciding which areas to prioritize for conservation, or even accepting that some trees will be lost.

Jad: 12:20

It's a balance between hope and realism, between fighting for what we can save and adapting to the changes that are happening.

Lilly: 12:28

I think that's a really good way to put it. It's not about giving up, it's about being strategic.

Jad: 12:33

So, for everyone listening out there, what are some things you can do right now to help protect ash trees in your area?

Lilly: 12:40

Well, the most important thing is to stay informed, keep up with the latest research and the best practices for managing the disease. There are great resources available online and through organizations like the Forestry Commission.

Jad: 12:52

And don't be afraid to ask for help. You know, reach out to experts and colleagues. This isn't something we can solve alone. We need to work together.

Lilly: 12:58

Exactly. Share your knowledge, share your experiences and we can learn from each other.

Jad: 13:03

And something as simple as just paying attention can make a big difference. Get out there and really look at the ash trees in your area, Notice their health, how they're growing and look for any signs of the disease.

Lilly: 13:14

Early detection is so important. The sooner we can identify infected trees, the better chance we have of stopping the spread and protecting the healthy trees.

Jad: 13:23

And remember, even small actions can have an impact.

Lilly: 13:26

It's all about making that commitment to the long-term health of our ash trees and our forests as a whole.

Jad: 13:31

This has been such an insightful conversation, even though it's a tough topic. Thank you so much for sharing your expertise with us today.

Lilly: 13:37

It's been my pleasure and thank you for asking these important questions and for your dedication to this issue.

Jad: 13:43

And to all of you listening. Thank you for joining us on this deep dive into the world of ash dieback and never lose hope for the future of our forests. We'll see you next time.

Roger: 13:55

Thank you for joining us Today. We reviewed key research on European ash health, examining the combined effects of Agrelis planipennis and Hymenocyphus fraxinius, the link between earlier regeneration and higher survival rates, and the role of Armillaria sapistipes in ash decline in northern Lithuania. We appreciate your attention and look forward to further discussions. Thank you.