Hi there, I'm Mrs. Kemp and welcome to today's lesson, all about plant diseases and specifically Chalara ash dieback.

This is part of the health and disease unit.

Okay, let's get started then.

So today's lesson, our main outcome is I can describe examples of common diseases in plants, how they spread and ways to reduce the spread.

These are some of the key terms that we're going to be using today, and if you would like to read those in more detail, please do pause the video.

But do rest assured I will explain each one of them as we move through the slide deck.

We've got two learning cycles for today.

We've got Chalara ash dieback and also food security and biodiversity.

We're going to begin with Chalara ash dieback.

So let's remind ourselves about communicable diseases.

These are types of diseases that are caused by pathogen and they can be passed from organism to organism and these are caused by microorganisms and specifically, they can include viruses, bacteria, and also fungi.

Now as well as animals, actually pathogens can also infect plants and those are what we were going to be focusing on today.

An example of a plant disease then is Chalara ash dieback.

And here is our native version of the ash tree.

It's called fraxinus excelsior and it's very, very common in this country, in the UK and in fact, it makes up most of our woodland here.

It's actually being threatened at the moment by a particular type of disease called Chalara ash dieback.

And you can see in the image there that tree has lost a lot of its top canopy, okay? It hasn't got any leaves growing in that top area and we've got some branches that are actually dead or dying.

It's caused by a fungus and you can see the actual part of the fungus there on that image, and those are the parts that release spores into the atmosphere and so that they can travel around.

Now, if any of these spores end up landing on some of the leaves, they can be infected in the sort of time of the year, of the late summer.

And first thing that will happen is that these little brown lesions will start to appear on the leaves.

You can see that in the image there.

And also we might get some brown lesions, some patches on the actual stems and twigs, and you can see there on the main trunk of the tree, we've got quite a big patch appearing.

Eventually this will lead to the wilting, so the shrivelling up of those leaves and eventually the dieback of any shoots.

This unfortunately will eventually lead to death of that tree, and so we lose the entire tree.

So what actually is a spore? A fungal spore is actually the main reproductive unit of a fungus.

They're very, very similar to seeds.

So wherever they land, they can actually then grow into a new fungus.

Just like with seeds, when they're carried around and they reach favourable conditions, they can then grow into a new plant.

Now, the Chalara ash dieback fungal spores can actually remain in the leaf litter, so leaves that have fallen from the trees over the winter and then actually they can be picked up by the wind and eventually stick onto the leaves of the different trees.

And when they do that, they do then infect the leaves of the ash tree and can grow into that fungus.

Okay.

Can you order the statements of Chalara ash dieback infection? A, brown lesions appear on the twigs and leaves.

B, the fungus releases spores into the air.

C, eventually the infection spreads through the plant and can lead to death.

D, the spores stick to the leaves and infect them.

Okay, I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay.

Did you think, one, the fungus releases spores into the air.

Two, the spores stick to the leaves and infect them.

Three, brown lesions will appear on the twigs and leaves.

Four, eventually the infection spreads through the plant and can lead to death.

Excellent.

Well done.

Okay.

So at the moment, there isn't actually any cure for Chalara ash dieback.

And it's thought that actually approximately 5% of the populations of ash trees are actually able to withstand the disease.

We think that this is maybe something to do with genetic factors, so maybe they've got some sort of mutation that means that the fungus is not able to kill it, and because of that then, we're not being advised to remove living trees like we might be with other fungal infections.

And that's because there is a chance that it might survive.

And if it does, we would really like that to be able to reproduce and produce more trees that have got that genetic mutation.

The trees are really essential for providing habitat for other organisms that live in that woodland, and they are a really, really important species to us in the UK.

So how can we actually slow down the spread if we can't cure it? So if you are visiting areas that have ash trees in, so woodland areas, it's advisable that you park on hard surfaces and not grassy areas where you're going to get some of that plant material potentially stuck to your tyres.

If you take bikes and cars into areas of woodland, it's advisable that you try to remove any obvious debris including twigs and leaves that may actually be carrying the fungus.

Also, if you work for a forestry and what you would need to be doing is trying to collect up any fallen ash leaves where we know that that spore can survive and burn that along with twigs in order to be able to disrupt the fungal lifecycle.

Okay, onto our next check then.

This one is true or false.

5% of the ash tree population can survive Chalara ash dieback infection.

Is that true or is that false? Can you justify your answer? They have a genetic susceptibility to the disease or they potentially have genetic factors that mean they can survive the disease.

I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay.

Did you realise that that was true? Excellent.

And that is because they potentially have genetic factors that mean they can survive the disease.

Excellent.

Really well done.

Okay.

Onto our first task of the day then.

This is task A.

You can find this on your worksheet.

You have been hired as a forest manager.

You have noticed that some of the ash trees have become infected with Chalara ash dieback.

Design a poster to put at the forest entrance to inform people about the disease and how they can help prevent the disease.

I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay.

Did you think of the pathogen is the fungus? Some of the symptoms then, brown lesions on stems and leaves can lead to death of the ash tree.

Treatment, there isn't unfortunately a treatment available at the moment, but you can help to prevent the spread by cleaning forest debris from the car and bike tyres, parking on hard surfaces and not on the grass.

Okay.

Excellent.

Well done.

If you need to add anything else, please do pause the video.

So onto our final learning cycle of today then, food security and biodiversity.

So we've got a food chain here, and if you remember, food chains always start with a producer.

An example of a producer would be a plant, and that is because they're able to make their own food in the form of sugar through photosynthesis.

As well as providing food for the other creatures that live in the ecosystem, they also provide important shelter for them and homes as habitats.

And so, it's really important that we actually prevent the spread of plant diseases and protect this food and shelter.

Now, food security is a measure of the quantity and quality of food available.

So that is the amount and also how good it is to support households or whole communities.

So just people living in one home or it could be a village or it could be a country or actually worldwide.

In the UK, we're actually very lucky and we do tend to have fully stocked supermarkets.

If there's something that we can't find, there is usually a good alternative for us to buy.

This unfortunately isn't the case around the world and there are still major shortages of foods in certain areas that can lead to starvation and death.

Okay, onto our next check, what do all food chains start with? A, a consumer, B, a producer, or C, a predator.

I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay.

Did you think B, a producer? Excellent.

Really well done.

So let's think about an example of a disease that actually led to a problem with food security.

Now, this is an old example.

It happened in the mid 1800 and affected potatoes.

It was caused by a fungus that led to potato blight.

Now at the time, a lot of the population in Ireland were consuming mostly potatoes in order to sustain themselves.

So it was a real staple food.

So when the potato blight hit, and so there were not enough potatoes available, it led to famine.

At the time it's estimated that 1 million people died of starvation during that famine.

So it really did hit the population hard.

It's actually very difficult to treat infections that are formed by funguses even today.

And really the only thing that you can do is remove infected parts of the plant and hope that it doesn't spread onto others.

So even if this occurred today, it would still actually be quite difficult to get rid of.

There is another case that is going on actually in modern day, and this is barley powdery mildew that is actually posing an ever increasing risk on food security.

Barley is a really important crop to us, and actually, it is a staple in many different products such as cereals, but also we find it in bread and sort of animal feeds.

And actually what the fungus does, this barley powdery mildew, it actually reduces the amount, so the quantity again and the quality of that grain for a farmer to be able to sell it.

What that does is it really drives up the price of barley and because there's less to sell to the same number of people.

What that means is that people living in situations of poverty may no longer be able to afford that food.

Now, often when we grow crops on farms these days, they tend to be genetically very similar or sometimes completely identical to each other.

That is what we know as a clone.

The reason that we do that then is that we can be more sure of the characteristics that they will have as a plant.

We also grow them very close together.

You can see on that lettuce farm there, they're very, very close and some may actually be touching.

What that means is, is that a disease can spread easily from one plant to another because they are in such close proximity.

When we grow one type of plant in an ecosystem like this, we call it a monoculture, mono meaning one.

Now, because they are all genetically very similar or identical, that means that if there is some sort of genetic weakness to a particular pathogen, they will all have that weakness.

And so essentially, that whole crop could be wiped out completely by just one type of pathogen.

The only really real way to help with this is to actually grow more than one type of crop at the same time, instead of just concentrating on having a monoculture.

Onto our next check then, this is which type of pathogen caused the potato famine? Is it A, bacteria, B, fungus or C, virus? I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay.

Did you think B, fungus? Excellent.

Well done.

So actually we still find this problem, even though they're not monocultures in natural ecosystems, these pathogens, especially new ones that are maybe coming over from different places, really pose a high risk for wild plant communities.

And our example of Chalara ash dieback really represents this.

So actually this disease is thought to have originated in Eastern Asia and it's been probably bought over by plant material or seeds, something along those lines.

Scientists are predicting that we may lose 80% of our ash trees in the UK, so it's absolutely huge.

However, the fungus doesn't seem to harm the Japanese Ash.

And remember, we think some of our population may also have a genetic mutation that means that they're able to survive it.

Now, ash trees are really important in their communities.

They do provide a lot of shelter and also food for many other organisms. So without them, they could probably die.

And we call this diversity within a ecosystem, biodiversity.

Let's break that word down a little bit then.

So bio meaning related to living organisms, diversity, the variety of things.

So biodiversity is the variety of living things in an area.

Globalisation of our food industry has really had a devastating effect on the spread of plant diseases around the globe.

And it's thought that probably when seeds and other plant material make its way into the country, this is how these plant diseases are really spread from one place to another.

Any material that is being bought into a country must therefore be checked and inspected to make sure that it isn't carrying some kind of disease.

And if the disease is suspected, then the plant material should be removed and safely disposed of maybe incinerated, so burnt.

Sometimes though, you're not going to be able to see whether or not that plant material has got a spore on it.

You'd only be able to see it if it had obviously been infected.

Okay.

Which of these ecosystems do you think has the greatest biodiversity? A, B, or C? I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay.

Did you realise it's C, that lovely woodland there is going to have many different types of organism and so you've just got a completely natural habitat with lots and lots of different organisms. Okay, onto our final task of the day then, this one is task B.

Please do open up your worksheet so that you can record your answers on there.

So how could you help to improve food security for the people of Ireland during the potato famine? I'll give you a moment to think about it, but if you need more time, please pause the video.

Okay.

So did we think of all of these things? First of all, we should remove infected parts of the plant and destroy them.

The farmers should look to grow another type of plant as well as the potatoes to avoid a monoculture.

They should make sure that any plant material entering the country is inspected for infections.

And if a disease is suspected, the material should be removed and then disposed of.

If you need to add in more to your answer, then please do that now.

Otherwise, we have almost come to the end of our lesson today.

So just before we finished, I would like to go through the key learning points with you.

Pathogens are microorganisms that cause disease.

Different types of bacteria, fungi and protists can all cause disease in plants.

An example of a fungal disease in plants is Chalara ash dieback.

Food security can be threatened by plant diseases that can spread around the world.

The loss of plants can lead to an overall loss of biodiversity in ecosystems. I really enjoyed today's lesson and there's been many new things for us to learn.

I hope that you've enjoyed it as well, and I hope to see you again soon.

Thanks so much.

Bye.