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Kyle Broderick - Turfgrass Diagnostics
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My name is Kyle Broderick,
extension educator with the University of Nebraska
and coordinator of the Plant & Pest Diagnostic Clinic.
I'd like to welcome you to the turf diagnostics portion
of our 2020 Virtual Turfgrass Field Day.
And without further delay, let's dive right in.
So you may be wondering why the diagnostics matter.
Well, say we head out into the landscape
or into the golf course early in the morning,
and we start to see some aerial mycelia that are growing
across the turf, wonder boy,
this is probably the start of one of our fungal pathogens,
but what could it be?
And as we start racking our brains
and thinking about diseases that may cause this dollar spot,
and maybe Pythium blight will be the first two
that come to mind.
Unfortunately, the management
for these two diseases is very different.
There's different fertility recommendations
for both of them.
Additionally, the fungicides
that dollar spot responds to are not the same fungicides
that Pythium blight will respond to.
So knowing what pest we are dealing with is
always the first thing that needs to be determined
before we do any sort of management recommendations.
Here, we have some more aerial mycelium
and this one is a little bit further progressed.
So we may start wondering is this dollar spot?
Is this Pythium blight?
But then in addition to the aerial mycelia,
we're also seeing some of that greasy
kind of water soaked turf there as well.
So maybe now we can start leaning
much more towards Pythium blight,
but all of this is to say that diagnostics matter
and correct identification is the important first step
that should guide any management recommendations.
Some of these diseases are very common.
We see them year in and year out.
They have very typical symptoms.
And so we're able to identify
them pretty readily based on that visual diagnosis.
Others are not so common
and maybe they're a little bit more difficult
to differentiate out in the field.
But the important thing to remember when we are doing
any sort of diagnostics,
especially when we're doing diagnoses
based on visual symptoms, pathogens, pests, they can't read,
they don't know what symptoms they're supposed to cause.
We pathologists do, we've done the research,
we know what brown patch is supposed to look like.
Rhizoctonia, the fungus
that causes brown patch does not know
what symptoms it should cause.
And whenever we have new cultivars that are coming out
or someone usual weather,
then we can start seeing
some usual symptoms occurring as well.
And so if we are seeing unusual symptoms
or we're just not sure what pest
or disease we're dealing with,
maybe we'll wanna start thinking about sending the sample
into a diagnostic clinic for confirmation.
And if we ever are thinking about sending the sample
in for confirmation, it is a very, very, very important
to make sure that we are collecting a high quality sample,
the higher quality the sample,
the higher quality our diagnosis will be.
And so for best results, we ask that you take a sample
as soon as you start to notice symptoms.
The earlier we catch these diseases and these problems,
the more tools we have at our disposal to help fight them.
We also wanna make sure that we're collecting
that sample before any fungicides have been applied.
One of the worst things that can happen is
to apply a fungicide, go back out three hours later,
collect that sample to send into a diagnostic clinic.
These chemical products are effective.
They often, they will kill the fungus
or at least knock back the fungus that's causing the issue.
If I get a sample into the clinic
that's already been sprayed with the fungicide,
I am unable to recover that fungus in the diagnostic clinic.
So again, making sure that that sample is collected prior
to fungicide application is very, very important.
As far as the size of the sample,
we ask them, just go ahead and use a cup-cutter
or cut a similar size plug of turf,
but something about four to five inches
in diameter often helps.
But we'll want something that includes the roots, stolons,
and leaf tissue, just so we are able to look
at that entire plant.
Often, injury that we see to the leaves
or blades may be a result of injury of disease
on the roots or on roots or crown tissue.
And please take a sample from the edge of the symptoms.
So about 2/3 of that sample should come
from the diseased area while the other 1/3
of that sample comes from the healthier area.
Having those two different portions of turf to compare
really help us dial in on what is causing injury
and what the disease of concern is.
And we always recommend to expedite shipping,
maybe doesn't necessarily need overnight,
but at least within a two-day shipping,
anytime a sample sits in a plastic bag
for an extra couple of days,
all sorts of things start growing on that sample.
And by the time it gets to a diagnostic clinic,
we may not be able to determine
what has actually caused the injury.
We also ask that you take pictures of the site.
So in case by the time the sample gets
to the diagnostic clinic,
it looks different.
Well, then we can go back to those pictures
and see what it looked like in the field
that will also help give us an idea to see
what's the overall landscape is looking like.
And maybe there are some environmental factors
that are coming into play too.
But real quickly, just a little bit of terminology here.
First, a disease, really disease is abnormal development
that interferes with plant structure
and/or plant function.
So really a disease is anything that prevents a plant
from operating at its maximum capacity.
An infectious disease is caused by a pathogen
that reproduces and spreads from plant to plant,
very different than a non-infectious disease.
Non-infectious diseases are a biotic diseases are caused
by non-living or environmental factors.
This could be weather,
this could be amount of moisture, this could be nutrition,
this could be compaction,
really anything non-living is a non-infectious disease.
Now, a pathogen is the biotic agent that causes
an infectious disease.
And so Rhizoctonia Solani is the pathogen
that causes the disease brown patch of turf.
A parasite is something that obtained some
or all of its nutrients from a living host.
And most of our pathogens are parasites.
I would compare that to a saprophyte,
while a saprophyte will live on that host
and live on that plant surface without causing any disease.
And so those saprophytes, those are what really become
an issue when we have a sample that has sat in a mail truck
or in a mail room for an extra couple of days.
The saprophyte really start to grow on the leaf tissue
and can even overtake some of our pathogens.
Now, as we're looking at our lawns or our landscapes
and trying to determine what we're seeing,
I always like to look at symptom distribution
from a few different scales.
And so we always start wide
and then just really narrow in and focus.
And so we always wanna start with our whole lawn
or whole landscape distribution.
Then we wanna look at symptoms on the individual plant,
where are we seeing these symptoms occur on the plant?
And finally, where on the individual plant parts are
these symptoms beginning to occur?
So as we're looking at the overall lawn,
one of the main things that we'll be looking
for are any patterns.
So patterns that may be due to lawnmower tracks,
or maybe there'll be maybe related to a walkway
where there would be some compaction issues, potentially.
Other things that we wanna look at when we're looking
at the whole lawn or landscape are,
we wanna be looking for any sort
of predisposing conditions
that may make the lawn
more susceptible to injury
from some sort of environmental condition.
This could be low spots or waterways, something like that.
But the big thing with the whole landscape
or lawn distribution, we really are looking for patterns.
And then as we focus in a little bit
and look at the symptom distribution with on the plant,
what plant parts are affected?
Are we seeing an injury to the leaves?
Is it the crown, or is it the roots,
and/or stolons that are primarily affected?
Different diseases tend to attack different parts
of the plant.
And so knowing which part of the plant is being affected can
really help us determine
what sort of pathogen we may be dealing with.
Now, along those same lines,
if we have a pathogen that only affects the foliage,
but does not affect the roots or crown tissue.
Well, as that plant continues to grow,
the disease portion of the leaf tissue
should grow out of that.
And so often, when we have diseases
that attack the crown or that attack the foliage,
but not the crown or root tissue,
those diseases, often will green back up in the middle
of those dead patches.
So we kind of have a little ring spot that can often form.
But finally, once we've looked at distribution
within the whole lawn,
within the individual plant,
now, we wanna be looking at the individual plant parts
and where are we seeing disease occur?
And so what do the lesions look like?
Are they spanning across the entire leaf blade,
or maybe they're only at the tip of the leaf blade,
or are they just kind of irregular
throughout the leaf blade?
Also, we wanna be looking at the margin.
Is it a very well defined margin
or is it kind of a leaky margin or maybe no margin at all?
Also, is there any color that we're seeing
with these lesions?
Again, these may not be able to tell us with 100%
certainty what the disease is,
but it helps us narrow things down for what the list
of suspects could potentially be.
But before we move too much further
into the different diseases,
have to discuss our disease triangle.
And so the disease triangle is the way that we integrate
our three components that are necessary
in order for disease to occur.
And so in order for disease to occur,
we need a favorable environment, a susceptible plant,
and a virulent pathogen.
Without any one of these three components,
disease will not occur.
Now, the important thing to remember about this though,
is we must have all three components occurring
at the same time.
If we have a virulent pathogen and a susceptible host,
but the environmental conditions aren't suitable right now,
we won't get disease until the environments become suitable
for that pathogen to cause infection.
So again, timing, the very critical fourth component
of our disease triangle.
So consequently, the amount of disease and length of time,
they overlap really impacts disease severity
and the extent of injury.
And so really the amount of disease is a direct function
of the amount of overlap of our three components
of the disease on disease triangle.
And so how much overlap do we have
between the suitable environment, the virulent pathogen,
and a susceptible host?
However, the impact on our plant is really a function
of the timing and the duration of that overlap.
And so if we only have a susceptible
or a suitable environment for just a short time,
we probably won't have a whole lot of disease that occurs.
Or if we had that suitable environment
at the end of the season, again, disease,
we won't be near as concerned about it.
Now, if we're having a lot of disease
that's occurring early on
or maybe as we're trying to establish new turf,
now that can be much more damaging
and much more severe.
So our diseases or especially our biotic diseases,
all biotic diseases are caused by pathogens.
The main groups of pathogens that we deal with are fungi,
bacteria, and viruses.
Now, there's some other groups of pathogens out there,
but at least in turf, fungi are primarily what we deal with.
In Nebraska, at least, we don't have a lot of issues
with bacterial diseases of turf,
nor do we have known issues of turf viruses.
There are some, however, just not a big issue in Nebraska.
Now, the nice thing about these fungal pathogens is
that they often do produce the mycelia or hyphae
and fruiting bodies to help us identify them.
These fruiting structures, maybe there'll be at,
maybe there'll be mushrooms like you would see
with a fairy ring,
or maybe it's just going to be spores that are formed,
or the little setae or the hairlike structures
that are common with anthracnose.
So the first disease that I would like to discuss
today is brown patch.
Brown patch is very common.
This disease affects many different types of turfgrass
and is caused by the fungal pathogen, Rhizoctonia Solani.
We typically see brown patch occurring really July
through August when we are having daytime temperatures
between 86 and 95 degrees Fahrenheit.
At nighttime temperatures that are
greater than 70 degrees are very important
for development of this pathogen.
We tend to see it occurring a lot more as well in areas
where there is poor air movement
and excess soil moisture.
And so this will be an ongoing theme.
A lot of our fungal pathogens require excess soil moisture
in order to cause infection.
And so one thing that we often try to manage is the moisture
and how long the soil,
how long the leaf blades will remain moist can really help
us determine what sort of diseases
may or may not be an issue.
But like I said, with brown patch,
we tend to see most of the injury with brown patch occurring
during periods that are hot and humid weather.
And we also have a lot of lush growth of the foliage.
And here, we just have a closeup
of our very prototypical lesion for brown patch.
So these tan irregularly shaped lesions
that have a dark brown border.
Normally, these lesions won't go all the way
across the leaf blade.
However, multiple lesions can coalesce
or grow together to look like
they are spanning the leaf blade.
Additionally, we can get this sort of patch
or this kind of irregularly shaped water soaked,
greasy kind of patchy areas in the lawn.
They're often gonna be maybe four to five inches
in diameter or larger.
And when there is morning dew, if we go out there,
we may be able to see some of that cottony,
cobwebby mycelia growth across the infected leaf blades.
Now, as far as management of this pathogen,
we used to recommend that we didn't wanna be using a
whole lot fertility in the summer as that rapid lush growth
of the turf was thought to increase the amount of disease.
Well, some recent research has been conducted,
both here at the University of Nebraska
and out in North Carolina has shown that fertility maybe
as important in managing brown patch.
And making sure that we're not letting that turf slow,
not letting that growth rate slow
drastically can help us from having a lot of issues
with this disease.
Additionally, we can over seed with resistant varieties.
And so bluegrass does tend to be a little bit more resistant
than fescue does for brown patch disease.
We also wanna make sure that we're not watering late
in the evenings.
Again, watering earlier in the day,
allowing time for that soil to dry out.
Well, it should decrease the amount of disease pressure.
And when we started thinking about any sort of fungicide
or chemical control, again, fungicide applications
at the first sign of disease are often effective.
And we tend to recommend a strobulurin
or or a Qol fungicides for four brown patch.
The next fungal disease that we're going
to discuss is dollar spot.
And so this one is caused
by this pathogens Sclerotinia homoeocarpa,
and this disease tends to affect really all
of our cool season turfs.
However, it is most common on bentgrass and bluegrass.
And here, we do have some pictures of the,
the bottom picture there,
we can see some of the cobwebby mycelium growth
early in the morning.
On the left, we have a picture of the patches,
often that are about the size of a silver dollar,
hence the name.
We pathologists are not brilliant namers,
we tend to be pretty boring in terms of naming things.
So initially for dollar spot,
those spots will be about the size of a silver dollar.
And I also have a picture which can kind of be made out here
of the lesions that are typical on the leaf blade,
where they tend to go across the leaf blade
and kind of girdle it.
But I have a few more that are captured right here.
And so often, we have these small,
maybe up to softball size patches
in the lawn that should have some of these light tan
to straw-colored leaf spots that will often span the blade.
Maybe the blade will even be a little bit pinched in there
where the lesion is occurring.
The dollar spot disease can be managed again,
similar to brown patch with resistant varieties,
work fairly well.
So over seeding with resistant varieties tends to help.
Also, if we can prevent excess soil moisture
or surface moisture, that will decrease the amount
of time that those blades of grass are wet,
decreasing the overall disease pressure.
Also wanna make sure
that we are providing adequate fertility.
And so not too much, not too little,
that we're removing excess thatch as well.
If we have a thatch buildup that can increase soil moisture
increasing disease pressure.
And we start thinking about a chemical control
for dollar spot, fungicides are also effective
for this disease.
However, there has been reduced sensitivity
to DMI fungicides that have been observed.
So when dealing with dollar spot,
we do recommend using a tank mix in order
to have some increased control for this pathogen.
The next one that we're going to work with is Pythium.
Pythium can affect all of our cool season turfs,
but it is more common on bentgrass and bluegrass.
There are many different species of Pythium
that can cause disease depending
on where we're seeing disease in some cases as well.
And so Pythium can cause both a foliar blight and a root rot
or a root dysfunction.
We tend to see different species of Pythium
primarily affecting the foliage
or primarily affecting the roots.
And this disease is much more common
in poorly drained, shady, wet areas.
And often with Pythium, we'll have some small circular spots
that suddenly occur in hot humid weather,
and then tend to enlarge at an alarming rate.
Often, there will be a water selter kind
of greasy appearance
as we have here in the bottom picture on the right side.
And here, we have a picture of one of the patches
that we would see with Pythium blight.
And so on the outside of this patch,
we are able to see some of that cottony mycelial growth
while on the inside, we have that dead greasy turf
that we're actually looking at.
Now, as far as controlling this disease,
it can be difficult to stay on top of.
So early detection, very, very critical for Pythium blight.
We really wanna make sure that we are doing
whatever possible to improve drainage,
improved soil drainage, improve surface drainage,
and also just air flow through the turf canopy,
avoid over fertilizing that cool season turf.
We also wanna avoid mowing wet grass as well
as that can help spread this,
that can help spread the disease.
And if we do know that we have a history of Pythium
and we have a forecast of hot humid weather,
that's predicted, then we probably wanna start thinking
about applying some sort of preventative fungicides,
just in order to stay on top of the disease issues.
Once we already have the disease occurring,
there are some curative products
that can be effective.
And so Segway is one that is fairly common.
If we are having high pressure,
we'll wanna be applying one of these curatives
about every seven to 10 days in order to keep
that disease pressure low.
And so Segway is one of the curative fungicides
that we have.
Cyazofamid is the active ingredient in that.
We also have Mefenoxam and Mefenoxam is
another active ingredient that historically has worked
very well against Pythium in some of oval mite seeds
or our water molds.
However, what we have found,
we have seen some reduced sensitivity
to Pythium with Mefenoxam as well.
So we are having a little bit of resistance
that is occurring.
And so again, we wanna make sure that we are rotating
these active ingredients as much as possible
and using tank mixes when we can.
The other thing that we want to keep in mind is
if we're looking at applying as azoxystrobin
or flutolanil for brown patch,
those active ingredients have actually shown
an increase in Pythium blight.
So if we have both brown patch and Pythium in an area,
maybe we would want to avoid using azoxystrobin if possible.
Next group of diseases,
we have summer patch and necrotic ring spot.
They look very, very similar, but they tend to occur
at different times of the year.
And so summer patch, we tend to see during the heat
of the summer, really July, August, and September.
Necrotic ring spot, we tend to see
really kind of may through October,
but that's often more May, June, July,
and September and October.
However, both of these diseases are common
when we have periods of hot dry weather.
So necrotic ring spot is most common
on Kentucky bluegrass caused
by the fungal pathogen, Ophiosphaerella korrae.
And so here, we do have some symptoms
of necrotic ring spot.
Again, very nice ring spots that are showing up
in the lawn that can be anywhere from a couple of inches
to a couple of feet in diameter compared with summer patch.
And so summer patch is caused
by the fungal pathogen, Magnaporthe poae.
And this is primarily found on bluegrass
and fine fescue as well.
And so with summer patch,
we may not get the rings that show up,
at least this first season,
we may not have the rings that show up.
If we have infections of summer patch over successive years,
that's when we'll tend to start seeing some rings,
but with summer patch,
as we look at these roots underneath the microscope,
one of the things that we tend to look
for are some black runner hyphae that are just going
along root zone.
And those are diagnostic for our summer patch disease.
Now, it's important to look
at that overall landscape as well,
not just the symptoms.
Here, have a nice patch in the lawn,
a little bit of a frog-eye symptom.
Maybe we'd be thinking necrotic ring spot or summer patch,
however, it's right next to the cement.
And this is actually heat stress due to the concrete.
And so again, knowing that entire landscape scene,
the larger wider environment, very, very important
when determining which disease we're dealing with.
We also tend to get,
if we would pull up these roots,
pull up these severely effected plants
and look at the root system,
we're going to see some very, very rotted roots
that are occurring here,
and maybe they would just be almost pure black.
And as we're trying to rinse them off, a lot of times,
those roots will kind of just disintegrate in your hands.
Now, as far as management for both summer patch
and necrotic ring spot,
best thing to do is reducing stress on established turf.
And so the fewer stresses that we have,
the more likely the turf will be able
to combat both of these diseases.
In the spring and early summer,
we can be looking at some systemic fungicide
that are effective.
We wanna maintain proper fertility
and maintain a proper mowing height as well.
Wanna make sure that we're managing thatch
and using improved cultivars
that may have some disease resistance bred in as well.
Again, using those that genetic resistance should
always be the first tool that's used
in combating any of these diseases.
Specifically with summer patch,
for preventative controls,
if we do have a severe history of this disease,
once the soil temps start to warm up.
So once we hit 65 degrees for six days,
then we can start to think
about a preventative fungicide application,
but we do want to avoid using DMI fungicides
really after June,
if we use these DMIs in July and August
when we were in the heat of the summer,
we can have some phytotoxicity that occurs,
and we don't wanna see injury due to that.
There are also some curative products
that can work for summer patch,
but these are most effective if started
as soon as symptoms begin to occur.
And so some of our strobulurin,
some of our azoxys work very against summer patch.
Also, wanna make sure that we're irrigating
after application to make sure that that fungicide is
actually getting down into the root zone
where the fungus is residing.
One thing regarding summer patch control is
if you are looking at repeated use of chlorothalonil
or iprodione in mid to late summer,
we've actually seen that that has led to an increase
in symptom development as well.
So just make sure that we are,
again, rotating these active ingredients
as much as possible,
not just using the same active ingredient,
greatly increases fungicide efficacy.
Not every one of these diseases that we see a fair amount
in Nebraska are leaf spot diseases,
and leaf spots and melting out.
And so these will hit our bluegrass's,
ryegrasses, and fescues.
A wide group of pathogens of fungal pathogens
that cause leaf spots.
So we have Bipolaris, Curvularia, Dreschslera, Exserohilum,
and then within each of these genuses of fungi,
there are many different species within each genus
that can cause these diseases as well.
And these to tend to show up
more in the early part of the season
and later in the season,
kind of when we're having a little bit cooler
and a little bit wetter temperatures.
However, they can also show up during the middle
of the season, if we do have cooler temperatures
for a few days along with wet weather.
And one of the things that we wanna be looking
at with these leaf spot diseases
and melting out are just some kind
of small purple-ish lesions on the blade.
They won't span the entire blade.
Often, they will be fairly circular,
but over time, we will start to then notice some thin areas
that are developing in the lawn and landscape as well.
And this is the melting out stage of this disease.
As far as management, again,
using some of those improved cultivars works
very, very well.
And so trying to use genetic resistance when possible,
also wanna make sure
that we are using proper fertility and irrigation.
And then as azoxystrobin
and fludioxonil are two active ingredients
that worked very well when applied in the spring
to help control leaf spot and melting out.
Another one of our fungal diseases
that we have seen a fair amount of in recent years
and this year as well is anthracnose,
Anthracnose is most commonly seen on annual bluegrass
and creeping bentgrass.
However, we can see it occur on most of our warm
and cool season grasses.
And again, this was a fungal pathogen caused by
or fungal disease caused
by the pathogen, Colletotrichum cereale.
And one of the things that is diagnostic
for anthracnose is if we look at it under magnification,
we'll actually see some setae
or just some kind of small black hairs
that are kind of sticking up out of the leaf
or out of the tissue as we have here in the bottom picture.
And the great thing about those setae is
that they are visible with your typical hand lens.
And so we can normally see those setae
at abour 10X magnification.
And so this is one that you can actually see out
in the field or out in the landscape.
But if we're not looking that closely,
maybe we're just looking at the overall lawn
and just seeing some of these spots
or patches that are occurring,
often, we'll have kind of a bronze
or maybe your reddish kind of orange purple,
purple color to these spots.
The other rough thing about anthracnose is
that it can attack really all parts of our plants
or all parts of our turf.
We can have anthracnose on the leaf blades,
we can have crown rot of anthracnose,
and we can have anthracnose on the roots.
The crown phase of anthracnose tends to be the foliar
and basal rot stages are, tend to be the most common,
but they are often just a result of overall stresses
that are occurring and anything that we can do
to decrease overall stress should decrease the amount
of anthracnose that we have.
So again, this disease is favored by high temperatures
and high humidity,
but it can occur over a wide range
of environmental conditions, especially when turf is facing
some other stresses.
We tend to see it more on, oh, if we see it,
if we're seeing anthracnose on some higher-cut turf,
normally that means there's some sort
of underlying predisposing factors at play
that are stressing the plant enough
to where they are unable to fight this fungal disease.
We see it a lot more when there is excessive soil moisture.
And when we have cool moist periods in the early spring,
followed by some extended overcast periods
in the late spring, that is perfect anthracnose weather.
And we should expect to see an outbreak occur.
Also, if we have higher organic matter in the soil
that can retain moisture,
increasing overall disease pressure.
If we have imbalanced fertility that can often cause
an increase in anthracnose as well.
Again, just because that's one more stress
that the turf is having to deal with.
So we wanna make sure
that there is sufficient soluble nitrogen,
wanna make sure that we're not dealing
with a potassium deficiency or any acidic conditions.
And so we wanna make sure
that that soil pH is not less than 5.8.
We also see anthracnose occurring in areas
where there is some mechanical injury as well.
So whether that's from verticutting or just traffic,
a little bit more anthracnose.
Management, again, using those resistant varieties
when possible works very, very well,
we wanna use those walk-behind mowers and raise the height
to reduce overall stresses.
And if there is a history of this disease,
maybe we'll wanna start thinking
about a preventative fungicide program.
And beginning of that fungicide program
about one month before we typically start
to see anthracnose starting to show up.
So if we're having a warmer winter,
maybe that's going to be about mid-March.
Any curative fungicide program should include
chlorothalonil also mixed
with a systemic fungicide to cut back
on that resistance pressure that may occur.
And again, these tank mixes work very, very well,
but we wanna make sure that we're avoiding
sequential applications of the same product.
Another disease that we have seen a little bit
of is ascochyta, this one
has a direct relationship to roots stress,
take care of the root stress,
you will take care of ascochyta.
The diagnostic symptoms
for this disease are the kind of the white
kind of needle appearance at the leaf tip
with kind of a ambiguous
or not not very well defined margin.
And as I mentioned, this disease is all about managing
that turf stress or that root stress.
And so here we have severe ascochyta blight
that's occurring earlier in this early in the year.
We took care of that root stress,
gave it a little bit more water, some more fertility,
and within two weeks we had a perfectly healthy green lawn
that that was occurring.
All because we had taken care of that root stress.
Now, additionally, when we are thinking
about using pesticides to manage these diseases,
we wanna make sure that we are reducing the risk
of pesticide resistance.
So we can do that by utilizing non-chemical disease
management when possible,
whether those are cultural controls
or using those resistant varieties.
We also wanna make sure that we're applying mixes
of different fungicide groups
and rotating those fungicide groups as possible,
if we're making multiple applications in a given season,
And we always wanna make sure that we are following
those label recommendations.
Remember, the label is the law.
And only apply pesticides when warranted based on scouting,
history, or forecasting.
And as far as developing fungicide resistance,
so fungicide resistant isolates are already out
in our populations,
and we get our fungicide resistant populations becoming
more common just because of natural mutations.
The important thing to remember is
that fungicides do not cause these mutations,
however, they do help select for these mutations.
And in fungi, we tend to have a natural mutation rate
of approximately one in every 100,000,000 spores,
so a fairly low mutation rate, but it can happen,
especially if we are heavily selecting
for these mutant resistant strains.
And just a few of the diseases that we have seen
that have gained resistance to some of our fungicides,
are dollar spot, powdery mildew, Pythium blight,
gray leaf spot, pink snow mold, and anthracnose.
And so a lot of the big ones that we deal with,
we have seen fungicide resistance occur.
So making sure that we're monitoring
and managing that fungicide resistance risk,
very, very important.
So the final thing that I would like
to leave you with is the accuracy
of any diagnosis is a function of the quality
of the sample collected and the thoroughness
of the background information provided.
And so making sure that we have a high quality sample,
and we know as much information about site history
and pesticide programs can really help us come
to a diagnosis quickly and rapidly.
And if you ever are uncertain about your diagnosis
and would like some help,
the Plant & Pest Diagnostic Clinic is here to help.
I mean, we have my contact information listed here.
So in addition to collecting samples by the mail,
we do have some drop box locations
where if someone is on campus
and would like to leave a sample,
they are more than welcome to.
With that, I would just like to say,
thank you for your time
and learning a little bit more about turf grass diagnostics.
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2020 Virtual Nebraska Turfgrass Field Day
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