Linking Brown Patch and Dollar Spot to Growth Rate

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07/30/2020 Added

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Dr. Bill Kreuser - Linking Brown Patch and Dollar Spot to Growth Rate

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[00:00:01.579](upbeat music)
[00:00:21.230]I'm Bill Kreuser, assistant professor
[00:00:23.560]department agronomy horticulture.
[00:00:26.740]All right. So this is a study that we've been doing
[00:00:28.220]now for two years.
[00:00:29.430]It was actually replicated last year,
[00:00:30.940]also at North Carolina state university with dr. Jim Kerns.
[00:00:34.660]And the whole goal of this study is
[00:00:36.240]to try to understand how growth rate
[00:00:39.280]and nitrogen status inside the plant impacts disease times.
[00:00:44.310]Uh, and so, uh, last year, dr. Kerns and I, uh,
[00:00:48.430]did this experiment
[00:00:49.490]and I replicated again here this year
[00:00:51.370]to get some extra data, uh,
[00:00:53.170]looking at how growth rate leads to
[00:00:56.140]Brown patch incidents in tall fescue.
[00:00:59.080]So may people probably heard,
[00:01:01.810]do not fertilize in the summer,
[00:01:03.730]uh, because the fear was
[00:01:05.370]if we put extra nitrogen fertilizer down,
[00:01:07.820]we get more Brown patch.
[00:01:09.420]And so what we've been seeing is more
[00:01:11.460]and more people not fertilizing the summer and having,
[00:01:14.550]you know, lawns that are really lean,
[00:01:16.920]uh, especially in newer lawns that have kind of
[00:01:19.480]poor soil organic matter
[00:01:21.680]and low potential to mineralize nitrogen from the soil.
[00:01:25.260]And those lines has got loaded with disease,
[00:01:27.800]Brown patch, dollar spot, things like that.
[00:01:31.180]And so it just, you know,
[00:01:32.280]about what you're seeing from historical recommendations
[00:01:34.320]was not aligning with what we were hearing
[00:01:37.417]or seeing in the field.
[00:01:39.060]And so what we decided to do with this study
[00:01:40.710]is, let's separate growth rate from fertilizer status
[00:01:45.530]in past studies that looked at Brown patch incidents.
[00:01:49.060]They found that more nitrogen fertilizer led to
[00:01:52.580]increases in Brown patch,
[00:01:53.900]especially in things like colonial
[00:01:55.980]and creeping bank grasses.
[00:01:57.820]Um, but the problem there is when you put out more nitrogen,
[00:02:02.460]you get more growth.
[00:02:03.850]And so it was a really a growth response,
[00:02:05.830]or is it more of infertility response?
[00:02:08.650]So in these studies that we're gonna talk about today,
[00:02:10.560]we'll start on this tall fescue,
[00:02:11.990]and then we'll go to a creeping bank,
[00:02:13.160]grass fairways we've manipulated growth rate
[00:02:16.150]with plant growth regulators.
[00:02:17.720]And so we have products like Primo max,
[00:02:20.120]or these are growth suppressor,
[00:02:22.370]and it's not to say pick up Primo
[00:02:25.208]it's just to say any type of product
[00:02:26.090]that's going to reduce the production of Jim Brown
[00:02:29.180]to make the grass grow slower.
[00:02:30.660]It's really simulating drought and soil compaction.
[00:02:33.370]So think about it that way.
[00:02:34.350]So this would be your kind of sore, poor soils plot.
[00:02:37.800]And then we have a pod that has no growth regulators.
[00:02:40.880]And then we have plots that are treated
[00:02:42.610]with kind of the anti Primo it's called rise up.
[00:02:45.400]It contains the hormone Gibberella.
[00:02:47.620]And so what we're doing here is we're actually stimulating
[00:02:50.510]greater lethal longation and more clipping yield.
[00:02:53.150]And then we took those three fertilizers or three PGRs
[00:02:56.150]and spread them across three different
[00:02:57.610]fertilizer treatments.
[00:02:59.220]So in this section, we have tall fescue.
[00:03:02.160]That's not getting any fertility
[00:03:03.810]and they still look okay because
[00:03:05.160]we have decent soils here on East campus.
[00:03:07.830]But if you took these plots to a new neighborhood
[00:03:10.010]that had a three, four soils,
[00:03:11.700]they would look really, really bad right now.
[00:03:14.660]Then we have plots that receive
[00:03:17.430]half a pound nitrogen every single month.
[00:03:20.210]This is from urea again, Primo, no Primo, GA bad soils,
[00:03:26.220]kind of medium good soils
[00:03:28.290]across the different fertility levels.
[00:03:30.310]And then the same thing here with a high level,
[00:03:33.322]were almost getting a pound
[00:03:34.927]for a thousand square feet,
[00:03:36.460]every single month being applied,
[00:03:38.110]we split into two apps to try to avoid any big surges
[00:03:41.290]or peaks or valleys.
[00:03:42.980]Um, but we noticed it's pretty clear.
[00:03:44.510]You look across the full plot areas that are getting Primo,
[00:03:48.700]that kind of simulating that soil
[00:03:51.730]uh, condition in which the grass would just be limited
[00:03:54.360]because it's dry and compacted
[00:03:56.270]and just not really good growing conditions.
[00:03:58.200]That's conditioned, it doesn't make gibberella.
[00:04:00.000]And just like what the Primo simulating here,
[00:04:02.190]they have pretty widespread Brown patch.
[00:04:04.560]Whereas the plots that are getting good amounts of growth
[00:04:07.350]have had fertilizer or putting a GA or actually growing,
[00:04:11.360]uh, you know, maybe through the Brown patch faster
[00:04:14.270]or that bad pathogen really easy.
[00:04:16.080]And you haven't having a time to really get going.
[00:04:18.770]You know, there's some of the, you know,
[00:04:20.630]the, the health of our pathologist can maybe
[00:04:21.690]understand more of what's going on,
[00:04:22.990]but from an ecology perspective that I deal in,
[00:04:25.560]I'm seeing that growth rate is having a huge impact
[00:04:28.670]on the amount of, of a brown patch.
[00:04:30.680]Cause we're seeing maybe a little bit
[00:04:31.960]here in the high fertility rate with the, uh, the Primo,
[00:04:35.620]but as we work our way back down
[00:04:37.160]to these lower fertility rates,
[00:04:39.440]we really see that it's just a lot of Brown patch
[00:04:42.650]on these plots just because they're just really not growing.
[00:04:46.580]So the take home point here
[00:04:47.750]really isn't think about how much fertilizer reporting down
[00:04:52.170]or we know PGRs or GA you know,
[00:04:54.700]you're not,
[00:04:55.533]I don't recommend putting down Jim or PGRs on your lawn.
[00:04:58.610]What I'm saying is we want to maintain healthy soils.
[00:05:01.610]We want to maintain a healthy growth rate.
[00:05:03.810]We want to try to get about an inch to an inch and a half
[00:05:06.150]of growth in the middle of the summer.
[00:05:07.880]If we're getting less than that,
[00:05:09.230]because we have poor soils or we're too lean,
[00:05:11.650]we need the fertilize.
[00:05:13.020]And if we're ready to getting well, and above that,
[00:05:15.350]we can back the fertilizer off
[00:05:17.050]because if you start going really high,
[00:05:18.610]that can be problematic too.
[00:05:20.000]So trying to manage towards the growth rate
[00:05:22.360]is really our goal.
[00:05:24.340]So now we've taken that same study design
[00:05:26.830]and we've applied it to creeping bank grass,
[00:05:28.760]fairways to diseases that are really, you know,
[00:05:31.530]in mind when we were designing this study,
[00:05:33.140]are dollar spot and the other one's Brown patch,
[00:05:35.970]we know from the literature that there's a good connection
[00:05:38.340]with low fertility kind of favoring dollar spot
[00:05:42.270]and high facility, favoring Brown patch.
[00:05:44.720]But the question that I still had
[00:05:46.780]the remaining question was,
[00:05:47.940]is it a growth rate effect or is it a fertility effect?
[00:05:51.540]And so we're trying to, again,
[00:05:52.860]decouple growth rate from fertility
[00:05:55.570]to get an idea of what is causing that.
[00:05:57.297]And so we have the same treatment set up here.
[00:06:00.610]The only difference here is slightly different rates on the,
[00:06:02.950]uh, on the, uh, fertilizer.
[00:06:05.700]So in this scenario, we're putting down, uh,
[00:06:08.520]15 hundreds of a pound or 0.3, uh, pensive,
[00:06:13.690]a pound every two weeks.
[00:06:15.220]So that is high as you would do on a lawn scenario, uh,
[00:06:19.510]just to rent the pot, the bank draft,
[00:06:20.720]I'm getting really puffy
[00:06:21.660]and assumably more realistic scenario,
[00:06:23.910]but again, we still have our three mode, a high rate.
[00:06:26.450]We have our non-treated with a PGR
[00:06:28.940]and our rise up to try to stimulate some growth rate.
[00:06:32.000]And we're seeing some really, you know,
[00:06:33.370]typical types of trends where the plots
[00:06:36.320]that are really being inhibited with a growth regulator
[00:06:40.260]are having a lot more dollar spots.
[00:06:42.190]So we can see a lot more dollar spot in this,
[00:06:44.710]which is getting treated with Primo.
[00:06:45.950]And again, the primo is not the cause
[00:06:47.640]it is simulating soil conditions.
[00:06:51.750]Then we have our non-treated control,
[00:06:54.660]with um, you know, a little bit less sour spot.
[00:06:56.650]And then we still have dollar spot,
[00:06:58.532]uh, on the, uh, uh, the Ryz UP treated,
[00:07:03.160]but we're also seeing some, some little bits of
[00:07:05.710]broad patch starting to form.
[00:07:07.460]And so we can really see how kind of managing
[00:07:09.910]that growth rate's important.
[00:07:11.150]So this was low fertility,
[00:07:12.440]no fertility actually in this plot,
[00:07:14.470]but it's with that rise up
[00:07:16.150]and we're starting to see the Brown patch.
[00:07:17.620]Then they come over to the next level of fertility,
[00:07:20.410]generally a little bit less a dollar spot
[00:07:23.860]on all the treatments.
[00:07:24.900]So we have a little bit here with a Primo,
[00:07:27.100]still not much at all and the notch, but there's nothing.
[00:07:30.570]And then the rise up, you know,
[00:07:32.160]it's a little bit of Brown, a dollar spot,
[00:07:34.330]and maybe it'll get a little bit Brown patch form
[00:07:36.230]cause it's starting to grow up pretty quickly.
[00:07:38.370]And then we go into the higher rate of fertility.
[00:07:41.050]So with the Primo a little bit more dollar spot
[00:07:44.200]than the control that doesn't have the Primo
[00:07:46.760]I, and this is fall, it's pretty clean.
[00:07:48.510]I don't really see anything,
[00:07:49.470]maybe $1 response center with the rise up,
[00:07:52.490]so it does show that there,
[00:07:54.090]there's probably some kind of a connection with,
[00:07:56.140]with fertility level.
[00:07:57.260]We are seeing them as a general reduction in dollar spot,
[00:08:00.300]um, as we've gone into higher fertility levels,
[00:08:03.130]but still that the growth rate is really important.
[00:08:05.520]And so making sure that we have other factors
[00:08:08.310]like moisture and good soil environments
[00:08:10.730]that promote good growth is further going to help
[00:08:13.040]to minimize, uh, uh, the dollar spot.
[00:08:16.150]And the, you know, the Brown patch piece
[00:08:17.490]is kind of interesting wherever we're trying to look
[00:08:19.790]at that a little bit more to understand we have known
[00:08:22.470]from some past applications,
[00:08:24.010]especially higher rates than Jim Maryellen,
[00:08:26.200]that we generally start to see some,
[00:08:27.700]some Brown patch filling in faster,
[00:08:29.610]even at low or high levels of nitrogen in fertilizer.
[00:08:32.640]So potentially there's some mechanisms going on
[00:08:35.530]there where that crashes is growing so rapidly,
[00:08:38.250]that it really isn't able to defend itself.
[00:08:40.420]And maybe it's really spindly a thin leaf,
[00:08:43.340]a plant and that Brown patch,
[00:08:44.980]and really just seems to that light favor, that environment.
[00:08:49.530]So that Ben crest study, I just showed that's a newer,
[00:08:52.980]uh, implementation that has study unfortunately because,
[00:08:56.750]um, you know, recently I was out spraying
[00:08:59.350]the rise up and, uh, used a slightly higher than,
[00:09:03.160]uh, expected rate a miss application.
[00:09:06.360]And so this was originally where we did that study,
[00:09:09.430]but sometimes even when you make a mistake,
[00:09:11.240]you can learn and learn things, especially if you observe.
[00:09:14.990]So the one thing to really noticed too is,
[00:09:17.140]you know, these plots got very, very high rate of,
[00:09:20.250]of rhizome, uh, and, uh, you know,
[00:09:23.210]they're starting to come back, uh, but you know,
[00:09:25.760]when they split that that rise up was applied.
[00:09:27.950]He get some of that discoloration that kind of,
[00:09:30.010]that ed elation color,
[00:09:31.750]even at the correct rate that we saw before compared to,
[00:09:34.500]to this, uh, it can go pretty bad pretty quick.
[00:09:37.800]And so we want to be careful wherever we're using hormones,
[00:09:40.210]because we don't want to,
[00:09:41.790]uh, get to the point where just small quantities,
[00:09:45.010]we're talking about hundred of civil weight
[00:09:46.710]ounce of product can in the list of really large changes.
[00:09:49.710]And so it's kind of a little bit of ,
[00:09:51.650]a thing we've noticed from that.
[00:09:53.520]Uh, but as these plots are starting to not recover,
[00:09:56.490]we are starting to see some differences across
[00:09:58.710]he's gonna miss applications, where we're seeing,
[00:10:01.190]you know, more Brown patch again,
[00:10:03.260]uh, in areas that are growing very rapidly.
[00:10:06.030]We're not seeing it in areas that are treated with Primo
[00:10:09.230]or not treated with a PGR.
[00:10:11.430]And so it really is showing the importance
[00:10:13.330]of that growth rate connection with that grass
[00:10:15.430]is just really growing at a really rapid rate
[00:10:19.140]or a really slow rate because of fertility
[00:10:21.930]or other environmental factors,
[00:10:23.730]the pathogens are gonna take advantage.
[00:10:25.250]And so when you're thinking about,
[00:10:26.860]you know, controlling pass, it's important to think about,
[00:10:29.880]you know, how you're using your products
[00:10:31.410]and what products to use and rotating.
[00:10:33.090]It's all great.
[00:10:34.160]But we also need to think about how are we minimizing
[00:10:37.070]the risk of having a problem with that particular test.
[00:10:39.720]And so growth rate is a good way to do that.
[00:10:42.040]So people are doing like clipping volume
[00:10:43.930]or even just kind of monitoring how frequently
[00:10:46.250]they have to mow their lawns.
[00:10:47.840]Those are ways that we can be a little bit better managers
[00:10:51.210]to help to achieve those clipping yield goals
[00:10:53.190]and minimize our diseases.

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Linking Brown Patch and Dollar Spot to Growth Rate

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