Turfgrass Diagnostics

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08/04/2020 Added

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Kyle Broderick - Turfgrass Diagnostics

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[00:00:01.265](upbeat music)
[00:00:12.240]Hello, everybody.
[00:00:13.100]My name is Kyle Broderick,
[00:00:14.470]extension educator with the University of Nebraska
[00:00:17.330]and coordinator of the Plant & Pest Diagnostic Clinic.
[00:00:21.300]I'd like to welcome you to the turf diagnostics portion
[00:00:24.310]of our 2020 Virtual Turfgrass Field Day.
[00:00:27.800]And without further delay, let's dive right in.
[00:00:32.100]So you may be wondering why the diagnostics matter.
[00:00:36.210]Well, say we head out into the landscape
[00:00:39.281]or into the golf course early in the morning,
[00:00:42.320]and we start to see some aerial mycelia that are growing
[00:00:46.060]across the turf, wonder boy,
[00:00:49.870]this is probably the start of one of our fungal pathogens,
[00:00:53.780]but what could it be?
[00:00:56.100]And as we start racking our brains
[00:00:58.470]and thinking about diseases that may cause this dollar spot,
[00:01:02.420]and maybe Pythium blight will be the first two
[00:01:04.500]that come to mind.
[00:01:06.420]Unfortunately, the management
[00:01:09.950]for these two diseases is very different.
[00:01:13.790]There's different fertility recommendations
[00:01:15.950]for both of them.
[00:01:17.300]Additionally, the fungicides
[00:01:19.740]that dollar spot responds to are not the same fungicides
[00:01:24.030]that Pythium blight will respond to.
[00:01:26.600]So knowing what pest we are dealing with is
[00:01:29.770]always the first thing that needs to be determined
[00:01:32.730]before we do any sort of management recommendations.
[00:01:36.740]Here, we have some more aerial mycelium
[00:01:39.580]and this one is a little bit further progressed.
[00:01:42.300]So we may start wondering is this dollar spot?
[00:01:44.570]Is this Pythium blight?
[00:01:45.870]But then in addition to the aerial mycelia,
[00:01:48.400]we're also seeing some of that greasy
[00:01:51.230]kind of water soaked turf there as well.
[00:01:54.450]So maybe now we can start leaning
[00:01:56.270]much more towards Pythium blight,
[00:01:58.940]but all of this is to say that diagnostics matter
[00:02:03.740]and correct identification is the important first step
[00:02:07.460]that should guide any management recommendations.
[00:02:11.110]Some of these diseases are very common.
[00:02:13.530]We see them year in and year out.
[00:02:17.594]They have very typical symptoms.
[00:02:20.720]And so we're able to identify
[00:02:22.670]them pretty readily based on that visual diagnosis.
[00:02:28.060]Others are not so common
[00:02:30.360]and maybe they're a little bit more difficult
[00:02:33.355]to differentiate out in the field.
[00:02:37.600]But the important thing to remember when we are doing
[00:02:40.540]any sort of diagnostics,
[00:02:42.220]especially when we're doing diagnoses
[00:02:45.120]based on visual symptoms, pathogens, pests, they can't read,
[00:02:52.410]they don't know what symptoms they're supposed to cause.
[00:02:56.350]We pathologists do, we've done the research,
[00:03:00.576]we know what brown patch is supposed to look like.
[00:03:03.910]Rhizoctonia, the fungus
[00:03:07.440]that causes brown patch does not know
[00:03:09.930]what symptoms it should cause.
[00:03:11.960]And whenever we have new cultivars that are coming out
[00:03:15.310]or someone usual weather,
[00:03:17.160]then we can start seeing
[00:03:18.620]some usual symptoms occurring as well.
[00:03:21.860]And so if we are seeing unusual symptoms
[00:03:24.740]or we're just not sure what pest
[00:03:26.540]or disease we're dealing with,
[00:03:28.430]maybe we'll wanna start thinking about sending the sample
[00:03:31.710]into a diagnostic clinic for confirmation.
[00:03:35.140]And if we ever are thinking about sending the sample
[00:03:37.490]in for confirmation, it is a very, very, very important
[00:03:42.900]to make sure that we are collecting a high quality sample,
[00:03:46.920]the higher quality the sample,
[00:03:48.730]the higher quality our diagnosis will be.
[00:03:51.890]And so for best results, we ask that you take a sample
[00:03:56.200]as soon as you start to notice symptoms.
[00:03:58.900]The earlier we catch these diseases and these problems,
[00:04:01.970]the more tools we have at our disposal to help fight them.
[00:04:06.950]We also wanna make sure that we're collecting
[00:04:09.090]that sample before any fungicides have been applied.
[00:04:13.090]One of the worst things that can happen is
[00:04:16.410]to apply a fungicide, go back out three hours later,
[00:04:21.160]collect that sample to send into a diagnostic clinic.
[00:04:25.360]These chemical products are effective.
[00:04:28.470]They often, they will kill the fungus
[00:04:32.070]or at least knock back the fungus that's causing the issue.
[00:04:36.270]If I get a sample into the clinic
[00:04:37.890]that's already been sprayed with the fungicide,
[00:04:40.380]I am unable to recover that fungus in the diagnostic clinic.
[00:04:46.060]So again, making sure that that sample is collected prior
[00:04:50.020]to fungicide application is very, very important.
[00:04:54.850]As far as the size of the sample,
[00:04:56.730]we ask them, just go ahead and use a cup-cutter
[00:04:58.830]or cut a similar size plug of turf,
[00:05:01.700]but something about four to five inches
[00:05:03.760]in diameter often helps.
[00:05:05.900]But we'll want something that includes the roots, stolons,
[00:05:10.220]and leaf tissue, just so we are able to look
[00:05:12.620]at that entire plant.
[00:05:15.100]Often, injury that we see to the leaves
[00:05:19.420]or blades may be a result of injury of disease
[00:05:22.940]on the roots or on roots or crown tissue.
[00:05:26.850]And please take a sample from the edge of the symptoms.
[00:05:29.540]So about 2/3 of that sample should come
[00:05:31.730]from the diseased area while the other 1/3
[00:05:34.160]of that sample comes from the healthier area.
[00:05:37.090]Having those two different portions of turf to compare
[00:05:42.140]really help us dial in on what is causing injury
[00:05:47.670]and what the disease of concern is.
[00:05:50.550]And we always recommend to expedite shipping,
[00:05:55.060]maybe doesn't necessarily need overnight,
[00:05:57.410]but at least within a two-day shipping,
[00:06:00.500]anytime a sample sits in a plastic bag
[00:06:04.490]for an extra couple of days,
[00:06:06.340]all sorts of things start growing on that sample.
[00:06:09.760]And by the time it gets to a diagnostic clinic,
[00:06:12.390]we may not be able to determine
[00:06:16.137]what has actually caused the injury.
[00:06:19.240]We also ask that you take pictures of the site.
[00:06:22.810]So in case by the time the sample gets
[00:06:25.510]to the diagnostic clinic,
[00:06:27.310]it looks different.
[00:06:28.390]Well, then we can go back to those pictures
[00:06:30.820]and see what it looked like in the field
[00:06:33.220]that will also help give us an idea to see
[00:06:36.970]what's the overall landscape is looking like.
[00:06:39.480]And maybe there are some environmental factors
[00:06:41.850]that are coming into play too.
[00:06:44.530]But real quickly, just a little bit of terminology here.
[00:06:48.060]First, a disease, really disease is abnormal development
[00:06:52.540]that interferes with plant structure
[00:06:54.540]and/or plant function.
[00:06:56.140]So really a disease is anything that prevents a plant
[00:06:59.740]from operating at its maximum capacity.
[00:07:03.770]An infectious disease is caused by a pathogen
[00:07:07.500]that reproduces and spreads from plant to plant,
[00:07:11.390]very different than a non-infectious disease.
[00:07:14.230]Non-infectious diseases are a biotic diseases are caused
[00:07:19.490]by non-living or environmental factors.
[00:07:22.730]This could be weather,
[00:07:24.830]this could be amount of moisture, this could be nutrition,
[00:07:27.970]this could be compaction,
[00:07:29.840]really anything non-living is a non-infectious disease.
[00:07:34.200]Now, a pathogen is the biotic agent that causes
[00:07:38.050]an infectious disease.
[00:07:39.850]And so Rhizoctonia Solani is the pathogen
[00:07:45.440]that causes the disease brown patch of turf.
[00:07:49.780]A parasite is something that obtained some
[00:07:52.990]or all of its nutrients from a living host.
[00:07:55.550]And most of our pathogens are parasites.
[00:07:58.920]I would compare that to a saprophyte,
[00:08:01.350]while a saprophyte will live on that host
[00:08:04.660]and live on that plant surface without causing any disease.
[00:08:08.350]And so those saprophytes, those are what really become
[00:08:11.900]an issue when we have a sample that has sat in a mail truck
[00:08:15.690]or in a mail room for an extra couple of days.
[00:08:18.460]The saprophyte really start to grow on the leaf tissue
[00:08:22.250]and can even overtake some of our pathogens.
[00:08:26.850]Now, as we're looking at our lawns or our landscapes
[00:08:31.280]and trying to determine what we're seeing,
[00:08:33.740]I always like to look at symptom distribution
[00:08:36.420]from a few different scales.
[00:08:37.930]And so we always start wide
[00:08:39.600]and then just really narrow in and focus.
[00:08:42.930]And so we always wanna start with our whole lawn
[00:08:45.920]or whole landscape distribution.
[00:08:48.590]Then we wanna look at symptoms on the individual plant,
[00:08:51.480]where are we seeing these symptoms occur on the plant?
[00:08:54.630]And finally, where on the individual plant parts are
[00:08:57.890]these symptoms beginning to occur?
[00:09:00.920]So as we're looking at the overall lawn,
[00:09:03.304]one of the main things that we'll be looking
[00:09:05.300]for are any patterns.
[00:09:07.520]So patterns that may be due to lawnmower tracks,
[00:09:10.910]or maybe there'll be maybe related to a walkway
[00:09:14.940]where there would be some compaction issues, potentially.
[00:09:18.200]Other things that we wanna look at when we're looking
[00:09:20.450]at the whole lawn or landscape are,
[00:09:23.150]we wanna be looking for any sort
[00:09:24.550]of predisposing conditions
[00:09:28.490]that may make the lawn
[00:09:32.040]more susceptible to injury
[00:09:35.130]from some sort of environmental condition.
[00:09:37.870]This could be low spots or waterways, something like that.
[00:09:41.350]But the big thing with the whole landscape
[00:09:45.350]or lawn distribution, we really are looking for patterns.
[00:09:50.570]And then as we focus in a little bit
[00:09:52.520]and look at the symptom distribution with on the plant,
[00:09:55.520]what plant parts are affected?
[00:09:57.850]Are we seeing an injury to the leaves?
[00:10:00.100]Is it the crown, or is it the roots,
[00:10:02.710]and/or stolons that are primarily affected?
[00:10:06.370]Different diseases tend to attack different parts
[00:10:10.210]of the plant.
[00:10:11.550]And so knowing which part of the plant is being affected can
[00:10:15.120]really help us determine
[00:10:18.040]what sort of pathogen we may be dealing with.
[00:10:23.220]Now, along those same lines,
[00:10:24.700]if we have a pathogen that only affects the foliage,
[00:10:28.780]but does not affect the roots or crown tissue.
[00:10:31.980]Well, as that plant continues to grow,
[00:10:35.770]the disease portion of the leaf tissue
[00:10:39.260]should grow out of that.
[00:10:40.740]And so often, when we have diseases
[00:10:44.363]that attack the crown or that attack the foliage,
[00:10:49.180]but not the crown or root tissue,
[00:10:52.680]those diseases, often will green back up in the middle
[00:10:57.110]of those dead patches.
[00:10:58.410]So we kind of have a little ring spot that can often form.
[00:11:03.680]But finally, once we've looked at distribution
[00:11:06.190]within the whole lawn,
[00:11:07.440]within the individual plant,
[00:11:09.680]now, we wanna be looking at the individual plant parts
[00:11:12.930]and where are we seeing disease occur?
[00:11:15.330]And so what do the lesions look like?
[00:11:18.200]Are they spanning across the entire leaf blade,
[00:11:21.880]or maybe they're only at the tip of the leaf blade,
[00:11:24.880]or are they just kind of irregular
[00:11:27.440]throughout the leaf blade?
[00:11:29.490]Also, we wanna be looking at the margin.
[00:11:31.900]Is it a very well defined margin
[00:11:34.150]or is it kind of a leaky margin or maybe no margin at all?
[00:11:38.790]Also, is there any color that we're seeing
[00:11:40.780]with these lesions?
[00:11:42.720]Again, these may not be able to tell us with 100%
[00:11:46.010]certainty what the disease is,
[00:11:48.740]but it helps us narrow things down for what the list
[00:11:51.880]of suspects could potentially be.
[00:11:54.950]But before we move too much further
[00:11:56.990]into the different diseases,
[00:11:59.770]have to discuss our disease triangle.
[00:12:02.807]And so the disease triangle is the way that we integrate
[00:12:06.690]our three components that are necessary
[00:12:08.650]in order for disease to occur.
[00:12:11.000]And so in order for disease to occur,
[00:12:13.040]we need a favorable environment, a susceptible plant,
[00:12:17.300]and a virulent pathogen.
[00:12:19.950]Without any one of these three components,
[00:12:22.830]disease will not occur.
[00:12:25.230]Now, the important thing to remember about this though,
[00:12:28.660]is we must have all three components occurring
[00:12:31.450]at the same time.
[00:12:38.410]If we have a virulent pathogen and a susceptible host,
[00:12:42.290]but the environmental conditions aren't suitable right now,
[00:12:46.090]we won't get disease until the environments become suitable
[00:12:51.100]for that pathogen to cause infection.
[00:12:54.280]So again, timing, the very critical fourth component
[00:12:57.740]of our disease triangle.
[00:13:00.410]So consequently, the amount of disease and length of time,
[00:13:04.060]they overlap really impacts disease severity
[00:13:08.170]and the extent of injury.
[00:13:09.940]And so really the amount of disease is a direct function
[00:13:14.530]of the amount of overlap of our three components
[00:13:17.820]of the disease on disease triangle.
[00:13:20.500]And so how much overlap do we have
[00:13:22.640]between the suitable environment, the virulent pathogen,
[00:13:25.990]and a susceptible host?
[00:13:28.140]However, the impact on our plant is really a function
[00:13:33.950]of the timing and the duration of that overlap.
[00:13:37.210]And so if we only have a susceptible
[00:13:39.630]or a suitable environment for just a short time,
[00:13:42.730]we probably won't have a whole lot of disease that occurs.
[00:13:47.810]Or if we had that suitable environment
[00:13:49.650]at the end of the season, again, disease,
[00:13:52.910]we won't be near as concerned about it.
[00:13:55.430]Now, if we're having a lot of disease
[00:13:57.640]that's occurring early on
[00:13:59.130]or maybe as we're trying to establish new turf,
[00:14:02.220]now that can be much more damaging
[00:14:04.750]and much more severe.
[00:14:10.660]So our diseases or especially our biotic diseases,
[00:14:15.700]all biotic diseases are caused by pathogens.
[00:14:18.770]The main groups of pathogens that we deal with are fungi,
[00:14:23.140]bacteria, and viruses.
[00:14:24.960]Now, there's some other groups of pathogens out there,
[00:14:28.170]but at least in turf, fungi are primarily what we deal with.
[00:14:35.560]In Nebraska, at least, we don't have a lot of issues
[00:14:38.470]with bacterial diseases of turf,
[00:14:40.840]nor do we have known issues of turf viruses.
[00:14:44.370]There are some, however, just not a big issue in Nebraska.
[00:14:49.600]Now, the nice thing about these fungal pathogens is
[00:14:55.140]that they often do produce the mycelia or hyphae
[00:14:59.780]and fruiting bodies to help us identify them.
[00:15:03.760]These fruiting structures, maybe there'll be at,
[00:15:06.280]maybe there'll be mushrooms like you would see
[00:15:08.480]with a fairy ring,
[00:15:09.870]or maybe it's just going to be spores that are formed,
[00:15:13.630]or the little setae or the hairlike structures
[00:15:16.640]that are common with anthracnose.
[00:15:21.560]So the first disease that I would like to discuss
[00:15:23.660]today is brown patch.
[00:15:25.890]Brown patch is very common.
[00:15:28.430]This disease affects many different types of turfgrass
[00:15:32.080]and is caused by the fungal pathogen, Rhizoctonia Solani.
[00:15:36.840]We typically see brown patch occurring really July
[00:15:39.950]through August when we are having daytime temperatures
[00:15:44.360]between 86 and 95 degrees Fahrenheit.
[00:15:48.040]At nighttime temperatures that are
[00:15:50.100]greater than 70 degrees are very important
[00:15:52.920]for development of this pathogen.
[00:15:55.990]We tend to see it occurring a lot more as well in areas
[00:15:59.620]where there is poor air movement
[00:16:01.850]and excess soil moisture.
[00:16:03.830]And so this will be an ongoing theme.
[00:16:07.150]A lot of our fungal pathogens require excess soil moisture
[00:16:11.150]in order to cause infection.
[00:16:13.490]And so one thing that we often try to manage is the moisture
[00:16:18.270]and how long the soil,
[00:16:20.280]how long the leaf blades will remain moist can really help
[00:16:25.300]us determine what sort of diseases
[00:16:27.310]may or may not be an issue.
[00:16:30.200]But like I said, with brown patch,
[00:16:31.510]we tend to see most of the injury with brown patch occurring
[00:16:35.540]during periods that are hot and humid weather.
[00:16:39.880]And we also have a lot of lush growth of the foliage.
[00:16:46.500]And here, we just have a closeup
[00:16:48.970]of our very prototypical lesion for brown patch.
[00:16:53.390]So these tan irregularly shaped lesions
[00:16:56.840]that have a dark brown border.
[00:16:59.480]Normally, these lesions won't go all the way
[00:17:01.850]across the leaf blade.
[00:17:03.530]However, multiple lesions can coalesce
[00:17:06.390]or grow together to look like
[00:17:08.500]they are spanning the leaf blade.
[00:17:11.650]Additionally, we can get this sort of patch
[00:17:15.030]or this kind of irregularly shaped water soaked,
[00:17:18.640]greasy kind of patchy areas in the lawn.
[00:17:22.340]They're often gonna be maybe four to five inches
[00:17:25.110]in diameter or larger.
[00:17:28.365]And when there is morning dew, if we go out there,
[00:17:31.520]we may be able to see some of that cottony,
[00:17:34.130]cobwebby mycelia growth across the infected leaf blades.
[00:17:40.860]Now, as far as management of this pathogen,
[00:17:45.396]we used to recommend that we didn't wanna be using a
[00:17:47.980]whole lot fertility in the summer as that rapid lush growth
[00:17:55.180]of the turf was thought to increase the amount of disease.
[00:17:59.560]Well, some recent research has been conducted,
[00:18:02.700]both here at the University of Nebraska
[00:18:05.580]and out in North Carolina has shown that fertility maybe
[00:18:10.310]as important in managing brown patch.
[00:18:15.740]And making sure that we're not letting that turf slow,
[00:18:20.100]not letting that growth rate slow
[00:18:24.120]drastically can help us from having a lot of issues
[00:18:30.079]with this disease.
[00:18:34.210]Additionally, we can over seed with resistant varieties.
[00:18:38.010]And so bluegrass does tend to be a little bit more resistant
[00:18:41.800]than fescue does for brown patch disease.
[00:18:45.800]We also wanna make sure that we're not watering late
[00:18:48.050]in the evenings.
[00:18:49.100]Again, watering earlier in the day,
[00:18:51.740]allowing time for that soil to dry out.
[00:18:56.720]Well, it should decrease the amount of disease pressure.
[00:19:00.490]And when we started thinking about any sort of fungicide
[00:19:03.100]or chemical control, again, fungicide applications
[00:19:07.140]at the first sign of disease are often effective.
[00:19:11.060]And we tend to recommend a strobulurin
[00:19:13.774]or or a Qol fungicides for four brown patch.
[00:19:18.890]The next fungal disease that we're going
[00:19:21.340]to discuss is dollar spot.
[00:19:23.970]And so this one is caused
[00:19:25.460]by this pathogens Sclerotinia homoeocarpa,
[00:19:31.200]and this disease tends to affect really all
[00:19:35.370]of our cool season turfs.
[00:19:36.980]However, it is most common on bentgrass and bluegrass.
[00:19:41.990]And here, we do have some pictures of the,
[00:19:45.450]the bottom picture there,
[00:19:46.550]we can see some of the cobwebby mycelium growth
[00:19:50.490]early in the morning.
[00:19:52.690]On the left, we have a picture of the patches,
[00:19:57.060]often that are about the size of a silver dollar,
[00:20:01.220]hence the name.
[00:20:02.053]We pathologists are not brilliant namers,
[00:20:05.540]we tend to be pretty boring in terms of naming things.
[00:20:08.550]So initially for dollar spot,
[00:20:10.860]those spots will be about the size of a silver dollar.
[00:20:15.400]And I also have a picture which can kind of be made out here
[00:20:18.900]of the lesions that are typical on the leaf blade,
[00:20:21.310]where they tend to go across the leaf blade
[00:20:24.220]and kind of girdle it.
[00:20:25.350]But I have a few more that are captured right here.
[00:20:30.670]And so often, we have these small,
[00:20:34.651]maybe up to softball size patches
[00:20:39.230]in the lawn that should have some of these light tan
[00:20:42.660]to straw-colored leaf spots that will often span the blade.
[00:20:48.198]Maybe the blade will even be a little bit pinched in there
[00:20:53.961]where the lesion is occurring.
[00:20:58.670]The dollar spot disease can be managed again,
[00:21:03.980]similar to brown patch with resistant varieties,
[00:21:07.240]work fairly well.
[00:21:08.340]So over seeding with resistant varieties tends to help.
[00:21:11.420]Also, if we can prevent excess soil moisture
[00:21:14.300]or surface moisture, that will decrease the amount
[00:21:17.410]of time that those blades of grass are wet,
[00:21:19.780]decreasing the overall disease pressure.
[00:21:23.150]Also wanna make sure
[00:21:24.210]that we are providing adequate fertility.
[00:21:26.717]And so not too much, not too little,
[00:21:30.410]that we're removing excess thatch as well.
[00:21:34.513]If we have a thatch buildup that can increase soil moisture
[00:21:38.830]increasing disease pressure.
[00:21:41.020]And we start thinking about a chemical control
[00:21:44.670]for dollar spot, fungicides are also effective
[00:21:49.060]for this disease.
[00:21:50.800]However, there has been reduced sensitivity
[00:21:53.710]to DMI fungicides that have been observed.
[00:21:56.880]So when dealing with dollar spot,
[00:21:59.290]we do recommend using a tank mix in order
[00:22:02.010]to have some increased control for this pathogen.
[00:22:09.000]The next one that we're going to work with is Pythium.
[00:22:13.666]Pythium can affect all of our cool season turfs,
[00:22:18.990]but it is more common on bentgrass and bluegrass.
[00:22:23.070]There are many different species of Pythium
[00:22:27.480]that can cause disease depending
[00:22:30.610]on where we're seeing disease in some cases as well.
[00:22:34.477]And so Pythium can cause both a foliar blight and a root rot
[00:22:39.020]or a root dysfunction.
[00:22:40.730]We tend to see different species of Pythium
[00:22:43.750]primarily affecting the foliage
[00:22:45.500]or primarily affecting the roots.
[00:22:49.040]And this disease is much more common
[00:22:53.750]in poorly drained, shady, wet areas.
[00:22:57.380]And often with Pythium, we'll have some small circular spots
[00:23:05.390]that suddenly occur in hot humid weather,
[00:23:08.790]and then tend to enlarge at an alarming rate.
[00:23:12.590]Often, there will be a water selter kind
[00:23:14.930]of greasy appearance
[00:23:17.440]as we have here in the bottom picture on the right side.
[00:23:22.620]And here, we have a picture of one of the patches
[00:23:26.760]that we would see with Pythium blight.
[00:23:29.780]And so on the outside of this patch,
[00:23:31.730]we are able to see some of that cottony mycelial growth
[00:23:35.830]while on the inside, we have that dead greasy turf
[00:23:39.420]that we're actually looking at.
[00:23:41.560]Now, as far as controlling this disease,
[00:23:45.470]it can be difficult to stay on top of.
[00:23:48.120]So early detection, very, very critical for Pythium blight.
[00:23:54.020]We really wanna make sure that we are doing
[00:23:56.350]whatever possible to improve drainage,
[00:23:59.200]improved soil drainage, improve surface drainage,
[00:24:02.600]and also just air flow through the turf canopy,
[00:24:06.100]avoid over fertilizing that cool season turf.
[00:24:09.890]We also wanna avoid mowing wet grass as well
[00:24:13.360]as that can help spread this,
[00:24:14.840]that can help spread the disease.
[00:24:17.800]And if we do know that we have a history of Pythium
[00:24:21.650]and we have a forecast of hot humid weather,
[00:24:24.650]that's predicted, then we probably wanna start thinking
[00:24:28.010]about applying some sort of preventative fungicides,
[00:24:32.240]just in order to stay on top of the disease issues.
[00:24:37.010]Once we already have the disease occurring,
[00:24:39.440]there are some curative products
[00:24:42.960]that can be effective.
[00:24:45.170]And so Segway is one that is fairly common.
[00:24:49.580]If we are having high pressure,
[00:24:51.110]we'll wanna be applying one of these curatives
[00:24:53.720]about every seven to 10 days in order to keep
[00:24:57.040]that disease pressure low.
[00:24:59.200]And so Segway is one of the curative fungicides
[00:25:02.250]that we have.
[00:25:05.850]Cyazofamid is the active ingredient in that.
[00:25:10.060]We also have Mefenoxam and Mefenoxam is
[00:25:14.270]another active ingredient that historically has worked
[00:25:17.020]very well against Pythium in some of oval mite seeds
[00:25:20.470]or our water molds.
[00:25:22.090]However, what we have found,
[00:25:24.450]we have seen some reduced sensitivity
[00:25:29.620]to Pythium with Mefenoxam as well.
[00:25:35.330]So we are having a little bit of resistance
[00:25:38.050]that is occurring.
[00:25:39.310]And so again, we wanna make sure that we are rotating
[00:25:42.030]these active ingredients as much as possible
[00:25:44.690]and using tank mixes when we can.
[00:25:48.070]The other thing that we want to keep in mind is
[00:25:52.660]if we're looking at applying as azoxystrobin
[00:25:55.660]or flutolanil for brown patch,
[00:25:58.870]those active ingredients have actually shown
[00:26:02.990]an increase in Pythium blight.
[00:26:05.670]So if we have both brown patch and Pythium in an area,
[00:26:10.650]maybe we would want to avoid using azoxystrobin if possible.
[00:26:18.540]Next group of diseases,
[00:26:19.800]we have summer patch and necrotic ring spot.
[00:26:22.330]They look very, very similar, but they tend to occur
[00:26:26.810]at different times of the year.
[00:26:28.770]And so summer patch, we tend to see during the heat
[00:26:31.900]of the summer, really July, August, and September.
[00:26:35.910]Necrotic ring spot, we tend to see
[00:26:39.180]really kind of may through October,
[00:26:41.040]but that's often more May, June, July,
[00:26:45.930]and September and October.
[00:26:48.260]However, both of these diseases are common
[00:26:51.150]when we have periods of hot dry weather.
[00:26:55.270]So necrotic ring spot is most common
[00:26:58.300]on Kentucky bluegrass caused
[00:27:00.640]by the fungal pathogen, Ophiosphaerella korrae.
[00:27:05.667]And so here, we do have some symptoms
[00:27:07.790]of necrotic ring spot.
[00:27:09.070]Again, very nice ring spots that are showing up
[00:27:14.060]in the lawn that can be anywhere from a couple of inches
[00:27:17.230]to a couple of feet in diameter compared with summer patch.
[00:27:23.037]And so summer patch is caused
[00:27:25.270]by the fungal pathogen, Magnaporthe poae.
[00:27:28.880]And this is primarily found on bluegrass
[00:27:32.440]and fine fescue as well.
[00:27:36.120]And so with summer patch,
[00:27:37.480]we may not get the rings that show up,
[00:27:41.060]at least this first season,
[00:27:42.400]we may not have the rings that show up.
[00:27:44.720]If we have infections of summer patch over successive years,
[00:27:48.910]that's when we'll tend to start seeing some rings,
[00:27:52.660]but with summer patch,
[00:27:54.680]as we look at these roots underneath the microscope,
[00:27:58.300]one of the things that we tend to look
[00:27:59.670]for are some black runner hyphae that are just going
[00:28:04.788]along root zone.
[00:28:07.220]And those are diagnostic for our summer patch disease.
[00:28:12.810]Now, it's important to look
[00:28:15.560]at that overall landscape as well,
[00:28:19.460]not just the symptoms.
[00:28:21.320]Here, have a nice patch in the lawn,
[00:28:25.360]a little bit of a frog-eye symptom.
[00:28:27.070]Maybe we'd be thinking necrotic ring spot or summer patch,
[00:28:31.810]however, it's right next to the cement.
[00:28:34.700]And this is actually heat stress due to the concrete.
[00:28:39.060]And so again, knowing that entire landscape scene,
[00:28:43.700]the larger wider environment, very, very important
[00:28:47.400]when determining which disease we're dealing with.
[00:28:50.600]We also tend to get,
[00:28:52.260]if we would pull up these roots,
[00:28:54.100]pull up these severely effected plants
[00:28:56.450]and look at the root system,
[00:28:58.150]we're going to see some very, very rotted roots
[00:29:02.730]that are occurring here,
[00:29:04.880]and maybe they would just be almost pure black.
[00:29:07.570]And as we're trying to rinse them off, a lot of times,
[00:29:10.500]those roots will kind of just disintegrate in your hands.
[00:29:14.510]Now, as far as management for both summer patch
[00:29:17.780]and necrotic ring spot,
[00:29:20.330]best thing to do is reducing stress on established turf.
[00:29:24.627]And so the fewer stresses that we have,
[00:29:28.400]the more likely the turf will be able
[00:29:32.246]to combat both of these diseases.
[00:29:36.400]In the spring and early summer,
[00:29:38.890]we can be looking at some systemic fungicide
[00:29:43.113]that are effective.
[00:29:44.820]We wanna maintain proper fertility
[00:29:48.292]and maintain a proper mowing height as well.
[00:29:51.420]Wanna make sure that we're managing thatch
[00:29:55.100]and using improved cultivars
[00:29:57.040]that may have some disease resistance bred in as well.
[00:30:02.030]Again, using those that genetic resistance should
[00:30:04.970]always be the first tool that's used
[00:30:07.980]in combating any of these diseases.
[00:30:13.680]Specifically with summer patch,
[00:30:16.030]for preventative controls,
[00:30:19.150]if we do have a severe history of this disease,
[00:30:22.450]once the soil temps start to warm up.
[00:30:24.650]So once we hit 65 degrees for six days,
[00:30:28.780]then we can start to think
[00:30:30.060]about a preventative fungicide application,
[00:30:32.820]but we do want to avoid using DMI fungicides
[00:30:37.520]really after June,
[00:30:40.900]if we use these DMIs in July and August
[00:30:45.620]when we were in the heat of the summer,
[00:30:47.670]we can have some phytotoxicity that occurs,
[00:30:50.940]and we don't wanna see injury due to that.
[00:30:55.730]There are also some curative products
[00:30:58.980]that can work for summer patch,
[00:31:00.700]but these are most effective if started
[00:31:03.120]as soon as symptoms begin to occur.
[00:31:07.440]And so some of our strobulurin,
[00:31:11.329]some of our azoxys work very against summer patch.
[00:31:16.650]Also, wanna make sure that we're irrigating
[00:31:18.720]after application to make sure that that fungicide is
[00:31:22.230]actually getting down into the root zone
[00:31:24.820]where the fungus is residing.
[00:31:28.230]One thing regarding summer patch control is
[00:31:32.690]if you are looking at repeated use of chlorothalonil
[00:31:36.050]or iprodione in mid to late summer,
[00:31:39.146]we've actually seen that that has led to an increase
[00:31:42.850]in symptom development as well.
[00:31:44.940]So just make sure that we are,
[00:31:47.390]again, rotating these active ingredients
[00:31:49.690]as much as possible,
[00:31:51.310]not just using the same active ingredient,
[00:31:55.080]greatly increases fungicide efficacy.
[00:32:02.640]Not every one of these diseases that we see a fair amount
[00:32:05.020]in Nebraska are leaf spot diseases,
[00:32:07.227]and leaf spots and melting out.
[00:32:09.387]And so these will hit our bluegrass's,
[00:32:11.480]ryegrasses, and fescues.
[00:32:14.340]A wide group of pathogens of fungal pathogens
[00:32:17.410]that cause leaf spots.
[00:32:19.170]So we have Bipolaris, Curvularia, Dreschslera, Exserohilum,
[00:32:25.170]and then within each of these genuses of fungi,
[00:32:29.410]there are many different species within each genus
[00:32:32.370]that can cause these diseases as well.
[00:32:35.690]And these to tend to show up
[00:32:40.169]more in the early part of the season
[00:32:41.990]and later in the season,
[00:32:44.250]kind of when we're having a little bit cooler
[00:32:46.130]and a little bit wetter temperatures.
[00:32:48.560]However, they can also show up during the middle
[00:32:50.980]of the season, if we do have cooler temperatures
[00:32:53.730]for a few days along with wet weather.
[00:32:58.470]And one of the things that we wanna be looking
[00:33:00.320]at with these leaf spot diseases
[00:33:03.170]and melting out are just some kind
[00:33:05.680]of small purple-ish lesions on the blade.
[00:33:09.300]They won't span the entire blade.
[00:33:11.550]Often, they will be fairly circular,
[00:33:15.290]but over time, we will start to then notice some thin areas
[00:33:19.530]that are developing in the lawn and landscape as well.
[00:33:22.920]And this is the melting out stage of this disease.
[00:33:27.100]As far as management, again,
[00:33:29.200]using some of those improved cultivars works
[00:33:31.740]very, very well.
[00:33:33.040]And so trying to use genetic resistance when possible,
[00:33:37.360]also wanna make sure
[00:33:38.320]that we are using proper fertility and irrigation.
[00:33:43.150]And then as azoxystrobin
[00:33:45.320]and fludioxonil are two active ingredients
[00:33:49.550]that worked very well when applied in the spring
[00:33:52.810]to help control leaf spot and melting out.
[00:33:57.230]Another one of our fungal diseases
[00:33:59.340]that we have seen a fair amount of in recent years
[00:34:03.040]and this year as well is anthracnose,
[00:34:07.440]Anthracnose is most commonly seen on annual bluegrass
[00:34:12.380]and creeping bentgrass.
[00:34:14.020]However, we can see it occur on most of our warm
[00:34:17.630]and cool season grasses.
[00:34:20.280]And again, this was a fungal pathogen caused by
[00:34:23.920]or fungal disease caused
[00:34:25.180]by the pathogen, Colletotrichum cereale.
[00:34:29.730]And one of the things that is diagnostic
[00:34:32.230]for anthracnose is if we look at it under magnification,
[00:34:37.560]we'll actually see some setae
[00:34:39.550]or just some kind of small black hairs
[00:34:42.340]that are kind of sticking up out of the leaf
[00:34:45.140]or out of the tissue as we have here in the bottom picture.
[00:34:49.379]And the great thing about those setae is
[00:34:53.420]that they are visible with your typical hand lens.
[00:34:57.310]And so we can normally see those setae
[00:35:00.110]at abour 10X magnification.
[00:35:02.790]And so this is one that you can actually see out
[00:35:05.110]in the field or out in the landscape.
[00:35:08.210]But if we're not looking that closely,
[00:35:10.070]maybe we're just looking at the overall lawn
[00:35:13.020]and just seeing some of these spots
[00:35:15.020]or patches that are occurring,
[00:35:18.030]often, we'll have kind of a bronze
[00:35:20.600]or maybe your reddish kind of orange purple,
[00:35:24.430]purple color to these spots.
[00:35:27.280]The other rough thing about anthracnose is
[00:35:29.940]that it can attack really all parts of our plants
[00:35:37.818]or all parts of our turf.
[00:35:39.650]We can have anthracnose on the leaf blades,
[00:35:42.730]we can have crown rot of anthracnose,
[00:35:45.400]and we can have anthracnose on the roots.
[00:35:48.780]The crown phase of anthracnose tends to be the foliar
[00:35:53.230]and basal rot stages are, tend to be the most common,
[00:35:57.830]but they are often just a result of overall stresses
[00:36:03.940]that are occurring and anything that we can do
[00:36:07.090]to decrease overall stress should decrease the amount
[00:36:10.770]of anthracnose that we have.
[00:36:14.200]So again, this disease is favored by high temperatures
[00:36:17.490]and high humidity,
[00:36:19.530]but it can occur over a wide range
[00:36:22.330]of environmental conditions, especially when turf is facing
[00:36:26.230]some other stresses.
[00:36:29.600]We tend to see it more on, oh, if we see it,
[00:36:32.760]if we're seeing anthracnose on some higher-cut turf,
[00:36:35.960]normally that means there's some sort
[00:36:37.920]of underlying predisposing factors at play
[00:36:41.460]that are stressing the plant enough
[00:36:43.560]to where they are unable to fight this fungal disease.
[00:36:49.660]We see it a lot more when there is excessive soil moisture.
[00:36:53.290]And when we have cool moist periods in the early spring,
[00:36:57.720]followed by some extended overcast periods
[00:37:00.520]in the late spring, that is perfect anthracnose weather.
[00:37:05.280]And we should expect to see an outbreak occur.
[00:37:08.480]Also, if we have higher organic matter in the soil
[00:37:11.470]that can retain moisture,
[00:37:15.070]increasing overall disease pressure.
[00:37:18.610]If we have imbalanced fertility that can often cause
[00:37:21.780]an increase in anthracnose as well.
[00:37:24.400]Again, just because that's one more stress
[00:37:28.708]that the turf is having to deal with.
[00:37:32.550]So we wanna make sure
[00:37:33.540]that there is sufficient soluble nitrogen,
[00:37:37.360]wanna make sure that we're not dealing
[00:37:38.850]with a potassium deficiency or any acidic conditions.
[00:37:42.450]And so we wanna make sure
[00:37:43.300]that that soil pH is not less than 5.8.
[00:37:47.890]We also see anthracnose occurring in areas
[00:37:51.290]where there is some mechanical injury as well.
[00:37:53.590]So whether that's from verticutting or just traffic,
[00:37:57.920]a little bit more anthracnose.
[00:38:00.700]Management, again, using those resistant varieties
[00:38:04.100]when possible works very, very well,
[00:38:07.470]we wanna use those walk-behind mowers and raise the height
[00:38:11.180]to reduce overall stresses.
[00:38:14.970]And if there is a history of this disease,
[00:38:17.600]maybe we'll wanna start thinking
[00:38:18.990]about a preventative fungicide program.
[00:38:21.600]And beginning of that fungicide program
[00:38:23.390]about one month before we typically start
[00:38:25.810]to see anthracnose starting to show up.
[00:38:29.040]So if we're having a warmer winter,
[00:38:31.630]maybe that's going to be about mid-March.
[00:38:36.100]Any curative fungicide program should include
[00:38:38.760]chlorothalonil also mixed
[00:38:42.543]with a systemic fungicide to cut back
[00:38:45.630]on that resistance pressure that may occur.
[00:38:49.230]And again, these tank mixes work very, very well,
[00:38:53.760]but we wanna make sure that we're avoiding
[00:38:55.410]sequential applications of the same product.
[00:38:59.250]Another disease that we have seen a little bit
[00:39:01.480]of is ascochyta, this one
[00:39:07.000]has a direct relationship to roots stress,
[00:39:10.610]take care of the root stress,
[00:39:11.930]you will take care of ascochyta.
[00:39:14.730]The diagnostic symptoms
[00:39:16.230]for this disease are the kind of the white
[00:39:20.490]kind of needle appearance at the leaf tip
[00:39:24.130]with kind of a ambiguous
[00:39:26.910]or not not very well defined margin.
[00:39:31.610]And as I mentioned, this disease is all about managing
[00:39:35.840]that turf stress or that root stress.
[00:39:38.910]And so here we have severe ascochyta blight
[00:39:42.290]that's occurring earlier in this early in the year.
[00:39:47.470]We took care of that root stress,
[00:39:50.080]gave it a little bit more water, some more fertility,
[00:39:52.820]and within two weeks we had a perfectly healthy green lawn
[00:39:57.710]that that was occurring.
[00:40:02.100]All because we had taken care of that root stress.
[00:40:05.940]Now, additionally, when we are thinking
[00:40:07.560]about using pesticides to manage these diseases,
[00:40:10.880]we wanna make sure that we are reducing the risk
[00:40:14.060]of pesticide resistance.
[00:40:17.200]So we can do that by utilizing non-chemical disease
[00:40:20.400]management when possible,
[00:40:21.980]whether those are cultural controls
[00:40:25.260]or using those resistant varieties.
[00:40:27.900]We also wanna make sure that we're applying mixes
[00:40:30.310]of different fungicide groups
[00:40:32.440]and rotating those fungicide groups as possible,
[00:40:36.470]if we're making multiple applications in a given season,
[00:40:39.877]And we always wanna make sure that we are following
[00:40:42.580]those label recommendations.
[00:40:44.220]Remember, the label is the law.
[00:40:47.680]And only apply pesticides when warranted based on scouting,
[00:40:52.230]history, or forecasting.
[00:40:55.833]And as far as developing fungicide resistance,
[00:41:00.770]so fungicide resistant isolates are already out
[00:41:07.150]in our populations,
[00:41:09.150]and we get our fungicide resistant populations becoming
[00:41:14.180]more common just because of natural mutations.
[00:41:18.900]The important thing to remember is
[00:41:20.133]that fungicides do not cause these mutations,
[00:41:24.540]however, they do help select for these mutations.
[00:41:28.200]And in fungi, we tend to have a natural mutation rate
[00:41:31.880]of approximately one in every 100,000,000 spores,
[00:41:37.510]so a fairly low mutation rate, but it can happen,
[00:41:42.560]especially if we are heavily selecting
[00:41:47.690]for these mutant resistant strains.
[00:41:54.670]And just a few of the diseases that we have seen
[00:41:57.430]that have gained resistance to some of our fungicides,
[00:42:02.730]are dollar spot, powdery mildew, Pythium blight,
[00:42:05.850]gray leaf spot, pink snow mold, and anthracnose.
[00:42:09.360]And so a lot of the big ones that we deal with,
[00:42:12.450]we have seen fungicide resistance occur.
[00:42:16.080]So making sure that we're monitoring
[00:42:18.020]and managing that fungicide resistance risk,
[00:42:21.140]very, very important.
[00:42:25.190]So the final thing that I would like
[00:42:27.690]to leave you with is the accuracy
[00:42:30.490]of any diagnosis is a function of the quality
[00:42:34.020]of the sample collected and the thoroughness
[00:42:37.020]of the background information provided.
[00:42:39.350]And so making sure that we have a high quality sample,
[00:42:43.200]and we know as much information about site history
[00:42:46.685]and pesticide programs can really help us come
[00:42:52.997]to a diagnosis quickly and rapidly.
[00:42:58.540]And if you ever are uncertain about your diagnosis
[00:43:01.440]and would like some help,
[00:43:02.630]the Plant & Pest Diagnostic Clinic is here to help.
[00:43:07.710]I mean, we have my contact information listed here.
[00:43:13.380]So in addition to collecting samples by the mail,
[00:43:16.670]we do have some drop box locations
[00:43:19.440]where if someone is on campus
[00:43:21.250]and would like to leave a sample,
[00:43:22.940]they are more than welcome to.
[00:43:25.030]With that, I would just like to say,
[00:43:26.640]thank you for your time
[00:43:28.570]and learning a little bit more about turf grass diagnostics.
[00:43:32.850]Thanks.
[00:43:33.683](upbeat music)

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Turfgrass Diagnostics

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