NICK VOLESKY: [INAUDIBLE] Claudia.
We picked tonight's topic on Fusarium diseases and tomatoes.
So I don't know if you guys remember last year all the news
headlines and chaos surrounding the tomato troubles.
A lot of growers had tomato problems,
and I know our program and Claudia's lab, especially,
received a lot of inquiries about tomato plants
with various symptoms like yellow leaves,
green leaves with purple veins, poor growth, or rolled leaves.
So I think the hype in the media, a lot of that
was associated with the curly top virus.
But, really, a lot of what we found,
it wasn't so much the virus, but it was more so
the prolonged cold temperatures that we had in May and June
that caused a lot of gardeners and farmers
having to wait to plant their tomatoes.
So this led to a lot of rootbound plants
and other poor root development.
But then that sudden increase in temperature
after that planting led to a growth spurt of above ground
while roots were unable to keep up.
So some tomato plants developed adventitious roots,
but the fine roots were unable to compensate
for the poor development of the primary roots.
And then tonight, I'll allow Claudia to share her screen.
But she's going to talk to us about some different diseases
we have in our tomato plants, especially Fusarium which
is very common here in Utah.
So, Claudia, I'll let you share your screen, and we'll--
CLAUDIA NISCHWITZ: Let's see.
NICK VOLESKY: --give it to you.
CLAUDIA NISCHWITZ: Can you all see it?
NICK VOLESKY: Yep.
You're all set.
CLAUDIA NISCHWITZ: All right.
So as Nick mentioned, last year we
had a lot of samples in my lab.
We received about 50 to 60 samples, tomato samples,
that all had pretty much the same symptoms.
They looked poorly grown, stunted, root development
was very poor, a lot of the roots were rootbound.
And I think if it had been a year where
you had still our normal growth, all these Fusariums
couldn't have caused as much damage as they did.
But if you have a poor root system to begin with,
and then the few roots that do develop get rotten by fungi,
there's nothing left for the plant
to take up nutrients and water.
And that then affects, of course, the growth.
So what we found last year in most of the tomato samples
that we received were several different Fusarium species
that cause different diseases on tomatoes,
and that's what I will be talking about tonight.
Out of all those samples that we received last year,
only three had actual curly top.
So that was a very low quantity for what we normally
get every year.
So Fusarium is a soilborne fungus.
There are several species that can infect tomatoes.
There are species that go to other vegetables,
but most of them are very host-specific.
So Fusarium oxysporum forma specialis lycopersici.
And you can see with the forma specialis lycopersici,
Lycopersicum is the scientific genus name for a tomato,
that this Fusarium species is specific to tomato.
So even though there is a Fusarium oxysporum that
can go to cucurbits, to melons, this one will not go to melons.
The one that goes to melons has a different form of specialis.
So you could still plant melons in that spot
if you had Fusarium oxysporum forma specialis lycopersici.
The second Fusarium oxysporum is forma specialis
radicis-lycopersici, which indicates that it will also
attack the roots of tomatoes.
And, again, this one is specific to tomatoes as well.
And the third one that we found was Fusarium solani.
Solani is a more widespread pathogen
and it goes to several different hosts,
especially in the Solanaceae family.
And a forma speciales is just a term
used to classify identical fungi that
differ in their host range.
Fusariums disperse by producing spores.
Sometimes you can see them as like a white or a pinkish mass
on the base of the stem.
And those spores when you look at them under the microscope,
they have this canoe shape to them,
which is very characteristic of Fusarium species.
They also produce resting spores called chlamydospores
that survive in the soil.
Those are those round spores, and they can survive
for several years in the soil.
So even if you rotate for five or six years out of tomatoes,
the spores would still be alive, and then
when you plant tomatoes again, they
would just be able to colonize the tomato roots.
So I will be talking briefly about all three diseases.
Fusarium wilt is caused by Fusarium oxysporum forma
specialis lycopersici.
We see it in Utah occasionally, but it's not
as common as the other Fusarium diseases.
As I mentioned, it is specific to tomato.
The symptoms look very similar to Verticillium wilt. That's
another soilborne disease.
The plants initially wilt during the hot part of the day,
but when it cools down in the evening,
they might initially recover.
So it looks like just some drought stress.
However, over time as the disease continues to progress,
the plant will be permanently wilting.
When you cut the stem and you look at the vascular
tissue, which is what you can see here,
this here is all brown, that's the diseased tissue.
If it was a healthy plant, it should be white.
So this is an indication of a vascular infection.
But Verticillium wilt will do the same thing.
So in order to differentiate between Verticillium wilt
and Fusarium wilt, you would need
to send a sample to a diagnostic lab
so the fungus could be cultured and then identified
what the causal agent is.
You also see the initial wilting.
This was a lot of what we saw last year, wilting,
yellowing of leaves, and dieback of leaves.
To manage Fusarium wilt--
using raised beds if you have a problem
persistently in your yard or on your small farm,
and line them either with plastic mulch
so they're not getting in contact
with the bare ground where you had the problem before,
or if you can raise the beds above ground and use soil
or a potting mix that has not been exposed
to any of these Fusarium.
So if you use compost, you want to make sure
that you know exactly what was put on that compost
because the Fusarium spores will most likely survive composting.
Especially because the compost does not
get hot enough in every spot to kill all the spores.
There are resistant varieties available for Fusarium
wilt, resistant tomato varieties.
And when you look at the label, so it will either
list Fusarium wilt and a 1 and 2 behind it as an indication
that there are several races of Fusarium wilt. There's, I
think, three right now.
And so this particular variety will
be resistant to races 1 and 2.
So my testing when I culture the fungi,
I can tell you it's Fusarium wilt,
I cannot tell you which race it is.
That is only something you can determine
by planting tomato varieties of different resistance levels
to see which ones are resistant to the race
that you have in the ground.
Or in some cases, the seller will abbreviate the disease
resistants with codes.
And if you have an F, that indicates
that it's resistant to Fusarium wilt. You
can go to this website from Cornell University,
they list all the--
or a lot of the tomato varieties with resistance levels
to a variety of different diseases,
including various Fusarium diseases, as well as
viruses and nematodes.
Now, if they are labeled as resistant with an F
or Fol for Fusarium oxysporum lycopersici,
they are only resistant to Fusarium wilt.
They are not resistant to any other Fusarium disease.
I had several commercial growers last year say,
well, I planted that variety, it's resistant to Fusarium.
And then when we looked up the variety,
it says it was resistant to Fusarium wilt but not
the actual Fusarium they had causing the problem.
There are no effective fungicides
for any of the Fusarium diseases.
So there's no need to apply fungicides.
It's just a waste of money.
Fusarium crown and root rot is caused
by Fusarium oxysporum forma specialis radices-lycopersici.
It's also specific to tomatoes.
The symptoms you see, just like with Fusarium wilt,
you will see wilting.
You will see vascular discoloration.
You see stunted growth.
But in addition to all of that, you will see a root rot.
You will not see a root rot with Fusarium wilt.
So that is a big difference.
If you pull up a plant and you see rotten roots,
you can already rule out Fusarium wilt.
And, again, you see the same symptoms
I showed you for Fusarium wilt, but in addition, you also
get this root rots.
If you look at this root, you can see here
that the cortex, the outer part of the root is missing,
and all you have is the inner core.
You can take your fingers and just gently pull along
the roots, and you often can just
pull that outer cortex of the root off.
To manage Fusarium crown and root rot,
again, use raised beds with either plastic mulch
covering the ground or raising the beds up above ground.
There are also no effective fungicides.
There are some resistant varieties,
tomato varieties available.
And they will have either FORL listed,
or it will be spelled out like I showed you before
in that other-- let me go back.
Like here, this variety is also resistant to Fusarium crown
and root rot.
Now, lastly, we have Fusarium foot rot.
Causal agent is Fusarium solani.
Its host range includes tomatoes, potatoes,
and peppers.
You will see lesions on roots, and you will see girdled roots.
You will see on the foliage, interveinal chlorosis.
You will not see vascular discoloration.
So here you can see the entire core of the roots rot.
And so this is the outer vascular tissue
that was rotten with the other two Fusarium diseases.
With Fusarium solani, the interior part of the root
is rotten all the way down to the roots.
And then you get this interveinal chlorosis,
which looks very similar to a nutrient deficiency, which
it actually is because with the rotten roots
and the rotten decaying stem, there is no nutrients coming up
into the plant that could be used by the plant for growth.
Fusarium foot rot is more difficult to manage.
There is no resistant varieties available.
So the only thing you can do is use raised beds with either
a plastic mulch, or raising them up above ground so that plants
cannot come into contact with the ground.
And since I mentioned that we need
to use good submit samples if you wanted to find out exactly
which Fusarium you have, or if it's Verticillium wilt and not
Fusarium wilt, you can submit samples to our diagnostic lab.
For pathogen culturing, they charge
$15 for the species identification of the Fusarium.
We would have to do DNA sequencing, which would then
cost you $30.
Oops, that was too fast.
You can go to our website, submit a sample.
We have different options for payment.
You can pay with cash, check, or we
can send you an invoice through PayPal so you can pay online.
We have a submission sheet we would
like you to fill in with as much detail as you can provide.
How many plants are affected?
What had you planted there last year?
Did you have problems last year in that same spot
maybe with another variety?
So if you have tomatoes this year
and the roots start to rot, and you had peppers last year
in that part, and they start rotting,
and we isolate a Fusarium, it could most likely
be Fusarium solani.
Let's see, what else do we need on that sheet?
How much you irrigate.
The variety of the tomatoes if you have it.
All this information can help us narrow down
and more easily determine which Fusarium
species you might have.
And, Nick, that was all that I had.
NICK VOLESKY: Awesome.
Thank you, Claudia.
So there's a few things I also wanted to share with you guys.
So last year, Claudia and I, we put together
this fact sheet on Fusarium and then the similar but different
Verticillium wilts that we have in vegetable.
So this is a really good guide where
we go in depth on the science of it, the different species,
symptoms and disease cycles.
And we cover all the vegetables, including our tomato crops.
And we cover a lot of the prevention and management
of where it's been diagnosed as well.
So this is a good resource for you to refer to.
And Claudia was mentioning different resistant varieties,
so we did put together a table where
we list some that are resistant to the different races
of Fusarium wilt. So you can see we have quite a few options
for tomatoes.
So if it's something you have a problem with,
I think this would be your number one
go-to is just planting something that's resistant.
Also, if you guys aren't familiar with,
we have our Abiotic Disorders of Tomatoes guidebook.
So this is something we put out, I think, a year or two ago.
We cover all the different problems
that can happen with your tomato plants that aren't a disease.
So this can include different abiotic things,
such as the weather and other nutrient deficiencies.
So we talk about adventitious growth, blossom drop,
and all sorts of different things.
So you can find this on our website.
Just go to extension.usu.edu/pest,
click Books and Guides, and then, alphabetically,
it will be your first one listed.
So definitely check out this guidebook,
Abiotic Disorders of Tomatoes.
So with--