Phytopthora

In this Thursday episode of Talking Trees, we focus on the global threat posed by Phytophthora species, aggressive plant pathogens that have devastated forests, gardens, and natural landscapes worldwide.

We discuss:

• The biology and life cycle of Phytophthora fungi-like organisms, including their ability to spread through water, soil, and infected plant material
• The impact of Phytophthora ramorum and Phytophthora kernoviae in the UK, with studies estimating significant public value at risk across woodlands and heritage landscapes
• Broader examples such as Phytophthora cinnamomi, responsible for widespread root rot in forest trees across Australia and the Americas
• Common symptoms of infection: crown thinning, bleeding cankers, dieback, and root decay
• The importance of early detection, biosecurity measures, and public awareness to limit spread and protect vulnerable ecosystems

Phytophthora continues to reshape forest health policy and underscores the need for vigilant, science-informed tree management.

Background information:

• Drake et Jones. 2017. Public value at risk from Phytophthora ramorum and Phytophthora kernoviae spread in England and Wale.pdf
• Hardy. 2004. Phytophthora Root Rot of Forest Trees.pdf

Chapters

• 0:00 Introduction to Phytophthora Threat
• 1:10 Sudden Oak Death and Global Impact
• 4:22 Economic Consequences of Phytophthora
• 6:28 Prevention and Biosecurity Measures
• 8:34 Treatment Options and Management Strategies
• 11:21 Conclusion and Call to Action

Transcript

Roger: 0:02

Talking Trees with Lily and Jad. Welcome to Talking Trees, your daily exploration into the challenges facing our natural world. In today's episode, we turn our focus to the fungal pathogens of the genus Phytophthora, a serious threat to forests and natural ecosystems around the globe, including in England and Wales. Ecosystems around the globe, including in England and Wales. Drake and Jones 2017, examined the economic impact of the spread of Phytophthora ramorum and Phytophthora carnovii, estimating significant financial losses linked to the damage of gardens, heaths and forests. Meanwhile, hardy 2004, offers a comprehensive overview of various Phytophthora species, detailing their life cycles, dissemination methods and the extensive damage they cause to forest trees across continents. Join us as we delve into these pressing issues and explore strategies to safeguard our green landscapes.

Jad: 1:10

Welcome back everybody. Today we're going to be taking a deep dive into something that I know is a big concern for all you arborists out there phytophthora it is. It's a pretty big, silent threat to our trees and, you know, as arborists, you're the ones that are really out there on the front lines.

Lilly: 1:22

Absolutely.

Jad: 1:22

We've got a couple of research articles today that we're going to be looking at Yep, and also a really interesting overview of phytothor root rot. So let's kind of unpack this a little bit and see what we can figure out and learn today.

Lilly: 1:35

Yeah, I think you know. The thing that is so striking about phytothor is that even for seasoned professionals you know, those of us who've been in the industry for quite a while it can completely change the game for us.

Jad: 1:49

Yeah, for sure. And it's not just you know a textbook pathogen we're talking about. You know a genus that can wipe out entire ecosystems, and I'm not being hyperbolic here.

Lilly: 1:59

This is the real deal. It's a serious issue.

Jad: 2:02

Yeah. So let's jump right in and talk about a case that I think really shook the arboriculture world Sure, sudden oak death.

Lilly: 2:10

Okay.

Jad: 2:11

Caused by Phytophthora remorum.

Lilly: 2:12

Yeah, phytophthora remorum is such a fascinating, horrifying but fascinating example, because you're talking about a pathogen that can actually spread through the air. Oh, in coastal regions of North America it's been. You know it's been devastating. It's causing rapid oak mortality, and it's not just oaks that are vulnerable to this. You know we're talking over a hundred susceptible species.

Jad: 2:36

Over a hundred, yeah, so what does that mean for arborists? What do they need to be thinking about?

Lilly: 2:41

Well, you know, vigilance is really keyed here, because you could have a tree that seems perfectly healthy one day and then all of a sudden you start seeing these signs of dieback. Phytophthora remorum is, you know, kind of a master of disguise in a lot of ways and its impacts can be very swift and severe.

Jad: 2:57

So knowing the signings is really crucial then.

Lilly: 3:00

Oh, absolutely. And this is where it gets really tricky because, you know, the symptoms of phytophthora can vary depending on the host and even the specific phytophthora species that you're dealing with. So you know, we might see root rot, we might see cankers, we might see wilking, but it's not always a very clear cut diagnosis.

Jad: 3:20

Right, and that's just one example.

Lilly: 3:22

There are other phytothorous species out there that are wreaking havoc as well in shortleaf pies, and the scope of its impact is really mind-boggling because over 3,000 plant species are known to be susceptible to phytophthora cinnamomi 3,000.

Jad: 3:53

That's almost impossible to even fathom.

Lilly: 3:56

It is and it really speaks to the interconnectedness of our ecosystems.

Jad: 4:00

Yeah.

Lilly: 4:01

You know, because when phytophthora cinnamomi infects a tree, it's not just about that one tree You're talking about, you know, disrupting the entire ecosystem, impacting soil, health, biodiversity, even affecting the animals that rely on those trees for habitat and food.

Jad: 4:16

It's like a domino effect.

Lilly: 4:17

It is.

Jad: 4:18

One that we, as arborists, really need to understand and be prepared for.

Lilly: 4:22

Absolutely.

Jad: 4:22

And to make things even more complex, this pathogen isn't confined to one continent.

Lilly: 4:27

Right.

Jad: 4:27

It's present in Europe as well.

Lilly: 4:29

Yeah, and the fact that you know Phytothororomorum was first described in Europe before it caused so much devastation in North America really highlights how easily these pathogens can travel.

Jad: 4:40

Yeah.

Lilly: 4:40

You know, we live in a globalized world and what happens in one forest can have a ripple effect on another forest on the other side of the planet.

Jad: 4:47

It's a good point that global perspective is really essential for arborists, especially in today's world.

Lilly: 4:53

Absolutely, and I think from a practical standpoint you know, understanding the economic impact of phytophthora can be really powerful when you're talking to clients.

Jad: 5:02

OK.

Lilly: 5:02

You know we have research here from the Journal of Environmental Management that estimates a staggering 1.446 billion pounds Wow, annual public value at risk in England and Wales alone. Wow, just from the uncontrolled spread of phytophthora remorum and Phytophthora carnovia.

Jad: 5:22

That's not just a number, though.

Lilly: 5:23

Right.

Jad: 5:23

What does that translate to in real world terms?

Lilly: 5:26

Think about heritage, gardens, woodlands, heathlands all of these are at risk. Wow, imagine having to explain to a client that their beloved oak tree- that's been the centerpiece of their property for years, has to be removed because of phytophthora. The cost of removal, replanting, the potential decrease in property value it all adds up.

Jad: 5:48

So it's not just about saving trees.

Lilly: 5:50

It's about so much more.

Jad: 5:51

It's about protecting investments.

Lilly: 5:52

Right.

Jad: 5:53

Preserving these landscapes and really understanding the true cost of inaction.

Lilly: 6:08

Exactly Preserving these landscapes and really understanding the true cost of inaction, how serious a threat phytophthora is, both in terms of its ecological impact and also economically. But now I think it's time to shift gears a little bit and talk about what we can actually do about it.

Jad: 6:24

Yeah, because knowledge is great, Right, but you know actually getting out there and putting it into practice and saving these trees is really what it's all about.

Lilly: 6:32

Exactly.

Jad: 6:33

So where do we even begin with something like this?

Lilly: 6:35

Well, it all starts with the basics, and I can't stress this enough Hygiene and sanitation are your first line of defense.

Jad: 6:40

Okay.

Lilly: 6:41

I know it sounds really simple, but you'd be surprised how often these fundamental practices are overlooked.

Jad: 6:47

What does that look like in practice?

Lilly: 6:48

Well, think about it, you're moving between job sites. Right, you're dealing with potentially infected trees.

Jad: 6:54

Right.

Lilly: 6:54

Every time you touch a branch, use your tools, even drive your truck from one location to another. You could be transporting phytothorous spores.

Jad: 7:02

So we're all potential carriers then? Essentially yes, unknowingly spreading this microscopic menace.

Lilly: 7:07

That's right, but the good news is we can break that chain. It's all about being mindful and implementing some simple but effective biosecurity measures.

Jad: 7:17

Okay, so give us some specifics. What could arborists do to you know? Stop those spores from hitting a ride.

Lilly: 7:23

Well, start with your toolers.

Jad: 7:24

Okay.

Lilly: 7:24

Make sure they're cleaned and disinfected between every single job.

Jad: 7:27

Okay.

Lilly: 7:27

Think about the soles of your boots, your truck tires anything that comes into contact with soil or plant material could be harboring phytophthora.

Jad: 7:36

So it's kind of like creating a clean slate before you move on to the next site.

Lilly: 7:39

Exactly.

Jad: 7:40

No one wanted souvenirs.

Lilly: 7:48

Precisely. And another important step is sourcing your plants from reputable nurseries that prioritize biosecurity. Don't be afraid to ask questions about their practices, their inspection protocols. You want to be confident that the trees you're planting are healthy and disease-free.

Jad: 7:59

It's all about due diligence.

Lilly: 8:01

Absolutely.

Jad: 8:01

Protecting your clients and their investments.

Lilly: 8:04

Exactly, and remember we talked earlier about the importance of early detection and reporting. Right, you're the eyes on the ground. If you see something suspicious, don't hesitate to reach out to your local plant health authorities.

Jad: 8:16

Okay.

Lilly: 8:17

Or diagnostic labs.

Jad: 8:18

So if a tree is showing symptoms, we shouldn't just assume it's something else.

Lilly: 8:22

Right.

Jad: 8:22

Better to get confirmation.

Lilly: 8:24

Exactly. A proper diagnosis is key. They can identify the specific phytophthora species, which can then guide your treatment decisions.

Jad: 8:31

Okay. So let's say we've got a confirmed case of phytophthora.

Lilly: 8:34

Okay.

Jad: 8:35

What happens next?

Lilly: 8:36

Well, the next steps depend on a variety of factors, sure, the severity of the infection, the species of the tree, the site conditions. But in many cases removing and destroying infected plant material is necessary to prevent further spread.

Jad: 8:51

Removal. That sounds a little drastic. I know, are there less extreme options?

Lilly: 8:56

Sometimes, if the infection is caught early enough and depending on the overall health of the tree, preening affected branches or roots might be an opaline.

Jad: 9:06

So kind of like a surgical approach.

Lilly: 9:08

Exactly Just targeting the diseased area, that's right, but it's important to emphasize that this must be done with extreme care.

Jad: 9:15

Okay.

Lilly: 9:16

And in conjunction with other management strategies. You don't want to create more wounds that could become entry points for further infection.

Jad: 9:23

Right, it's all about minimizing the risk of spreading those spores.

Lilly: 9:27

Precisely, and another important aspect of control is managing the site conditions to make them less favorable for phytophthora.

Jad: 9:35

Okay, how do we do that?

Lilly: 9:36

Well, we know that this pathogen thrives in moist, poorly drained soils, so think about improving drainage, avoiding overwatering, mulching appropriately.

Jad: 9:49

So it's about playing defense, creating an environment that's not a phytophthora paradise.

Lilly: 9:54

That's a great way to put it. You're essentially tweaking the environment to give the trees a fighting chance.

Jad: 9:59

And this is where an arborist's expertise really comes into play.

Lilly: 10:03

Absolutely.

Jad: 10:03

Right Understanding the specific needs of the trees and the site conditions.

Lilly: 10:07

You're not just treating the symptoms.

Jad: 10:09

Right.

Lilly: 10:09

You're creating a holistic management plan that considers the entire ecosystem.

Jad: 10:14

And speaking of tools in the toolbox, yes, we talked earlier about phosphonates, as what's the latest on those?

Lilly: 10:21

Well, phosphonates can be a valuable weapon against phytophthora.

Jad: 10:24

Okay.

Lilly: 10:24

Especially in severe cases or when you're dealing with highly valuable trees. They work by boosting the plant's natural defenses and inhibiting the pathogen's growth.

Jad: 10:35

But like with any chemical treatment, there are some potential downsides to consider.

Lilly: 10:39

There are, and responsible use is really key. One concern is phytotoxicity.

Jad: 10:45

Okay.

Lilly: 10:45

Essentially damage to the treat itself Right If the phosphonates are applied incorrectly or at too high a concentration.

Jad: 10:53

So knowing the right dosage and application method is crucial.

Lilly: 10:57

Absolutely. And another issue is the potential for resistance development in phytophthora populations if they're repeatedly exposed to the same chemical treatment.

Jad: 11:07

So it's a balancing act then. It is Using these tools strategically while minimizing the risks. Exactly what's the best way for arborists to stay informed about the latest research and guidelines on phosphonate use?

Lilly: 11:20

That's a great question. The research is constantly evolving.

Jad: 11:23

Right.

Lilly: 11:23

So continued education is really fruitful. Organizations like the Forestry Commission and FARA are excellent resources. They publish research findings, best practice guidelines and they even host workshops.

Jad: 11:35

So staying ahead of the curve is really essential in this battle.

Lilly: 11:39

It is.

Jad: 11:39

It's not just about knowing what to do. It's about knowing the latest and the most effective methods.

Lilly: 11:46

Exactly and don't underestimate the power of networking.

Jad: 11:49

Okay.

Lilly: 11:50

Talk to other arborists, share experiences, attend conferences Right the collective knowledge and expertise within the arboriculture community is invaluable.

Jad: 12:01

Powerful stuff. I think you know a lot of arborists feel that deep connection to the trees that they care for. It's more than just a job, Absolutely, it's a passion.

Lilly: 12:10

I couldn't agree more, and that passion is what's going to drive us forward.

Jad: 12:13

Yeah.

Lilly: 12:14

Even in the face of challenges like Phytophthora.

Jad: 12:17

Well, as we wrap up this deep dive, I want to thank you for sharing your expertise and insights with us today.

Lilly: 12:21

Oh, the pleasure was all mine.

Jad: 12:23

It's been a really eye-opening journey into the world of Phytophthora.

Lilly: 12:26

Yeah, it's a fascinating and complex topic, for sure.

Jad: 12:28

For sure To our listeners out there. We hope this deep dive has equipped you with the knowledge, sparked some new ideas and fueled your passion for protecting our trees.

Lilly: 12:37

Absolutely. Stay curious stay informed and keep up the amazing work you do, because together we can make a difference. Couldn't have said it better myself the amazing work you do, because together we can make a difference.

Roger: 12:45

Couldn't have said it better myself. Thank you for joining us on today's episode of Talking Trees. We've delved into the critical threat posed by phytophthora pathogens. As we continue to navigate these complex issues, we hope you take away the importance of proactive prevention and control measures in safeguarding our forests and natural ecosystems. Until next time, stay informed and committed to protecting our green world.