Tar Spot Presentation

Mariah Newmyer Author

03/05/2025 Added

2 Plays

Description

Dr. Tamra Jackson-Ziems speaks to Hamilton County community members about Tar Spot and other emerging plant diseases.

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[00:00:00.000]wonderful well thank you so much for attending our first extension board driven community
[00:00:08.740]engagement presentation um so today we're going to talk about tar spot and other emerging crop
[00:00:14.860]diseases um our extension board is a group of dedicated community members committed to promoting
[00:00:22.120]and advancing the mission of nebraska extension um so today is a perfect example of their
[00:00:29.580]dedication um bringing nebraska extension's expertise to you and to our community um so
[00:00:36.280]extension board members if you wouldn't mind please standing up a lot of them are in the back
[00:00:40.860]there kevin reason has done a ton of work for us thank you so much kevin but um if we could give
[00:00:47.160]them a little hand for putting on this
[00:00:48.720]and thank you so much to our wonderful sponsors for their generous support um for this presentation
[00:00:59.160]you can find a list of them on our promotional flyer our website and social media and i will
[00:01:05.600]be recording this presentation as well for those of you for those of us who couldn't um join today
[00:01:11.740]so i'm going to put that on our website but if you'd like a direct link to the presentation
[00:01:17.000]please let me know and i'll get your contact information um so without further ado i'm
[00:01:22.200]pleased to introduce our speaker tamra jackson designs um she is a specialist in the unl plant
[00:01:28.740]pathology department and leads research and extension efforts on tar spot in nebraska
[00:01:34.440]so tamra the floor is yours
[00:01:36.640]thank you so much i'm gonna unroot this microphone so i can walk around at least a couple feet
[00:01:48.000]um and try not to trip over it but i want to say thank you to all of you for
[00:01:52.780]making it out on this ugly morning and thanking our extension board i know
[00:01:58.320]it's a lot of work uh to do that and i really appreciate the efforts of everybody that worked
[00:02:04.760]on this and for your county extension i uh also want to thank your sponsors for making this happen
[00:02:11.060]and all the planning these events are sometimes laborious to put on and i also want to apologize
[00:02:17.300]because if you have to have a plant pathologist come talk to you that means things haven't been
[00:02:21.220]looking very good right and so i'm i better not stand by the speaker this is gonna mess up our
[00:02:28.000]sound
[00:02:28.300]and so um thanks to mariah for working this out with me i'm a specialist like she mentioned and
[00:02:36.060]so if you're not familiar with i guess the uh the network of extension uh i'm a specialist in the
[00:02:44.520]state and so to try to put that in perspective all i do are diseases and specifically i'm your
[00:02:50.540]corn pathologist for all of nebraska and so uh to kind of put that in perspective you know you
[00:02:58.020]it would be like your general practitioner when you go to the doctor steve melvin is your local
[00:03:03.300]general practitioner he's your county extension educator and he is a jack of all trades okay and
[00:03:09.700]so if there's anything you have questions about which is anything other than diseases i'm not
[00:03:15.600]going to be able to answer it probably and i'm going to turn to him and ask for help and so beyond
[00:03:20.640]him you know you have specialists that work on specific topics and so that's that's what i work on i
[00:03:27.740]also have counterparts i have a new soybean pathologist dylan mangel who's been here about
[00:03:32.620]three years and so although i covered soybeans for a little while now you have somebody dedicated
[00:03:38.740]because you need somebody to focus on that how many of you have had white mold in recent years
[00:03:44.020]white mold is a major issue and we need somebody working on that and soybeans this nematode and
[00:03:49.600]others and so uh we have other specialists too and so if you have any questions about extension
[00:03:55.280]please let us know and
[00:03:57.460]the stuff i want to share with you today is uh it's observations it's mainly i want to answer
[00:04:03.600]your questions i want to give you an idea of what you might expect in the coming years
[00:04:09.000]and unfortunately uh there's there's reason to be alarmed about some of this but i think if we're
[00:04:16.040]planning ahead we can cut off some of that potential damage and so um a couple of things
[00:04:23.120]here so she asked for a tar spot update so it makes
[00:04:27.180]complete sense i would first start talking about a hurricane right and so uh we talked about you
[00:04:33.700]know let's cover a little bit of the other diseases that were a big problem here recently
[00:04:38.280]and so this hurricane actually affected us even though we didn't directly have precipitation from
[00:04:45.860]it and you know i i barely paid attention although i did have something on my mind during that time
[00:04:52.300]a concern because of the track this storm took and so
[00:04:56.900]you might remember it was down in the gulf and it spun out over around galveston and then it
[00:05:02.240]and it took a turn and went up through the midwest and so am i standing in front of your
[00:05:06.320]green so you see it kind of took a turn up through midwest and so although we didn't get moisture out
[00:05:12.880]of it i want you to think about the other things those storms bring and so we were already getting
[00:05:18.940]some southerly winds southerly winds have an impact on us and this had an even bigger impact
[00:05:26.620]because the disease that i think was a much bigger impact for us in 2024 it wasn't tar spot
[00:05:34.200]it was probably southern rust did anybody come out of the field looking like you had
[00:05:39.060]all over you and for you folks down here in south central nebraska this isn't new to you
[00:05:46.040]is it you see southern rust every few years and some years it's pretty dang bad
[00:05:50.420]southern rust has a high potential to cause damage and so when this storm
[00:05:56.340]kind of spun up through the midwest it likely pushed a lot of those southern
[00:06:01.280]rust spores up our way but i honestly think we probably already had a little
[00:06:05.520]bit of it nearby and part of that is because you know this storm didn't make
[00:06:09.420]its way up here until july 8th through the 10th and during that three-day
[00:06:13.420]period it made its way up through look at the map all the way up through the
[00:06:19.000]great lakes region and so southern rust here's the good news of my talk as many
[00:06:26.060]of you know southern rust is caused by a fungus that cannot overwinter and so if
[00:06:31.280]you had a lot of southern rust this past year it does not mean that you're going
[00:06:36.020]to have it again this year and so that's the good news right and so it does not
[00:06:41.420]overwinter whether or not we have southern rust depends a lot on how much
[00:06:46.220]there is south of us how much wind pushes it up our way a lot of other
[00:06:51.300]conditions and so you know we're used to looking for these orange
[00:06:55.780]to tan spores you can see in the picture on the left-hand side of that
[00:06:59.440]screen most of those are produced on the top side of the leaf a little bit on the
[00:07:04.160]bottom too and again we see a little bit every year but it wasn't until I think
[00:07:11.800]let's see July then the week of July 19th so it was about three days before
[00:07:16.120]that suddenly I started getting calls text message direct messages and I
[00:07:22.680]started getting pictures of a lot of stuff that looked really
[00:07:25.500]a lot like southern rust and it wasn't a surprise to see it that early what was
[00:07:32.440]a concern for me and why I blew the whistle or rung the bell so to speak is
[00:07:37.680]because I was getting reports and then samples coming in from all around
[00:07:43.140]eastern Nebraska all the way up to the South Dakota border and that was unusual
[00:07:48.840]to see southern rust movement up into Nebraska that deep into Nebraska that
[00:07:53.640]early and
[00:07:55.220]so look at that it says spam on it should let one of you answer for me the
[00:08:01.760]concern to me about having southern rust come that early in particular in 2024
[00:08:07.680]because in a lot of parts of our state we had a lot of late planted corn where
[00:08:12.400]I live up in northern Nebraska most of our corn had not tasseled yet and so we
[00:08:18.080]were a little bit behind where we normally would be and when a disease
[00:08:22.280]moves in and especially if you
[00:08:24.940]haven't even gotten to the grain fill stages yet you have the potential to
[00:08:28.880]have enough disease to impact grain fill and so I don't like to say I push the
[00:08:34.640]panic button but I think 2024 on July 19th was as close as I've gotten to
[00:08:39.280]pushing the panic button some of you probably have been doing this for a few
[00:08:44.860]years now so how many of you remember 2006 and in 2006 we were definitely
[00:08:51.020]orange weren't we a lot a lot of southern rust that
[00:08:54.660]year I had just started the year before you know what I'd heard the words
[00:08:59.280]southern rust I heard somebody say oh you know southern rust it would confirm
[00:09:04.800]some and I thought oh okay I guess I better I'm here on a crop watch article
[00:09:09.600]right but it didn't really occur to me how bad that could be and in 2006 you
[00:09:14.540]might remember we had a lot of late planted corn that year to weather
[00:09:19.140]conditions were very favorable we had a cloudy stint really humid late late
[00:09:24.380]July early August southern rust blew up on us and at that time we weren't using
[00:09:29.960]a lot of fungicides but the people that tried fungicides at that point they were
[00:09:34.100]newer to us in corn the people that were more aggressive and attentive and tried
[00:09:39.480]it saw huge benefits from it on southern rust management the ones that didn't saw
[00:09:46.640]tremendous losses in yield and what happened at the end of the season it all
[00:09:52.040]fell down didn't it and so that's a
[00:09:54.100]secondary problem that we have with a lot of diseases and southern rust in
[00:09:58.000]particular and so we know the potential problems and so when we started seeing
[00:10:03.280]it all the way up into northern Nebraska as early as that second week in July I
[00:10:08.140]was pretty concerned and so a lot of you might have seen the the crop watch
[00:10:12.340]article the market journal video the YouTube videos
[00:10:15.880]oh there was Ag Almanac radio interviews and so those are all the ways that I can
[00:10:20.440]reach you and that's as quickly and efficiently as I can do it
[00:10:23.820]but it's to let you all know okay this is here we better start watching
[00:10:28.520]because you know it doesn't mean suddenly overnight we're going to have
[00:10:33.060]southern rust everywhere or tar spot for that matter
[00:10:36.020]it means over the next you know two three four weeks things might escalate
[00:10:40.980]especially in certain fields of high risk
[00:10:43.340]and so that's just kind of to add a little bit of interpretation on top of
[00:10:47.680]what I was announcing there and so that's what
[00:10:52.260]happened and we saw a little bit
[00:10:53.540]going on in Kansas and so I'm going to show you eventually what happened and so
[00:10:58.120]by the end of the season all the counties you see shaded in red on that
[00:11:02.000]map on the left will show you where it was confirmed well
[00:11:05.780]clearly I like not all these counties are lit up but it
[00:11:09.500]doesn't mean that you didn't have disease there
[00:11:11.720]and I want to thank everybody all of our crop consultants and agronomists
[00:11:16.860]and all of your help for helping us find diseases like this so that we can let
[00:11:21.500]people know where we're finding
[00:11:23.260]things and what to be on alert for and you can see there's a lot of gaps in
[00:11:27.540]maps like this and those are what I call human factors
[00:11:30.320]if nobody sends a sample and I can't light the map up so if you're seeing
[00:11:34.580]something please let me know please let Steve know we'll get samples and
[00:11:38.220]get it confirmed but you see it made it all the way up and across South Dakota
[00:11:44.200]it even made it as far north as Minnesota
[00:11:46.380]and so it did turn out to be a banner year for southern rust
[00:11:50.800]and so I
[00:11:52.980]think in parts of Nebraska that was definitely the worst disease
[00:11:56.540]but it's not the one that I'm most concerned about and so
[00:12:00.500]one thing to keep in mind about southern rust that I'm guessing a lot of people would have
[00:12:04.700]witnessed this year too was that the southern rust
[00:12:08.980]fungus makes those orange spores we all know what to look for
[00:12:12.720]when we see those out in the field but toward the end of the
[00:12:16.880]season that fungus tries to overwinter and it starts making
[00:12:20.680]a different type of spore.
[00:12:22.700]These are called telios spores and they're black.
[00:12:25.540]And so the black pustules then start to look a lot like tar
[00:12:31.340]spot.
[00:12:31.740]So a lot of people probably saw those black spots there at the
[00:12:36.900]end of the season and thought it was all tar spot blowing up.
[00:12:40.300]Some of it probably was.
[00:12:42.960]I don't think most of it was though.
[00:12:45.500]And so we had a lot of confusion going on there at the end of
[00:12:49.360]the season.
[00:12:49.840]And so in the picture on the left, that's southern
[00:12:52.420]rust.
[00:12:52.880]Now the differences in color between the two, that to me,
[00:12:57.260]that's kind of fake news.
[00:12:58.540]So this is a, this is probably an error in lighting because
[00:13:04.120]when they're on the same leaf, it's really hard to tell it
[00:13:07.180]apart.
[00:13:07.520]And I don't feel confident in it unless I can get it under
[00:13:11.520]a microscope, which I carry around with me most of the
[00:13:14.440]time.
[00:13:14.800]If you see old southern rust pustules or even common rust
[00:13:19.200]pustules with a black ring around it,
[00:13:22.140]or a horseshoe, it could be that teleospore stage,
[00:13:26.360]not tar spot.
[00:13:27.480]But if you can get that to somebody with a microscope,
[00:13:30.740]we can tell really quickly which one you've got.
[00:13:33.540]And so that's not important for treatment at that time of
[00:13:38.660]year.
[00:13:38.780]It's more about what's going to overwinter.
[00:13:40.620]The rust diseases won't overwinter on corn.
[00:13:43.760]So that's the good news.
[00:13:44.880]But the tar spot does.
[00:13:47.780]And so realistically, I'm far more concerned about
[00:13:52.380]tar spot because it does overwinter.
[00:13:55.220]This fungus doesn't care how cold it gets.
[00:13:58.820]You know, this is a fungus that's already overwintering
[00:14:01.620]extremely well in places like Michigan and Wisconsin
[00:14:05.720]and Minnesota.
[00:14:06.500]And so having a cold winter isn't going to help us
[00:14:10.460]with this fungus.
[00:14:11.340]It's still new to us, though.
[00:14:14.380]Here in the United States, you know, we've only been
[00:14:16.800]having tar spot since 2015.
[00:14:18.700]And that started over in Illinois
[00:14:21.580]and Indiana, and it spread from there.
[00:14:24.180]When it was new to them, it didn't appear that it was
[00:14:28.640]going to be a big threat.
[00:14:29.780]It didn't do much.
[00:14:31.300]It didn't increase in severity.
[00:14:32.480]It wasn't even moving much.
[00:14:33.900]And it took about three years before the fungus built
[00:14:38.060]up enough.
[00:14:38.560]We call that inoculum, before you had enough of it
[00:14:41.040]build up.
[00:14:41.600]And then we had a favorable growing season in Illinois,
[00:14:45.520]Indiana, and some of the states right around there.
[00:14:48.420]And it blew up then.
[00:14:50.120]And then it started to grow.
[00:14:51.300]And it started moving.
[00:14:52.160]And over the years now, they've documented yield loss as much
[00:14:57.060]as 50 bushels per acre.
[00:14:58.600]In Latin America, where this pathogen originated, they've
[00:15:04.040]documented more than that.
[00:15:05.300]And there's two or three different fungi that can cause
[00:15:09.420]and work together to cause tar spot now.
[00:15:12.320]We've only got one.
[00:15:14.200]That's plenty, right?
[00:15:15.360]And so just know we're monitoring that.
[00:15:18.420]We're watching the genetics of it, looking for changes.
[00:15:21.020]Now, these black spots, they look like tar.
[00:15:25.360]They look like somebody splattered black paint on the surface.
[00:15:28.220]And it can be on the bottom, too.
[00:15:30.760]As it matures, it makes it bigger and bigger.
[00:15:34.580]We call them stromata or stroma.
[00:15:36.500]That's the actual fungus.
[00:15:38.240]And that's where it's cranking out thousands of spores.
[00:15:41.740]And so every time we get rain splashing or irrigation splashing
[00:15:47.240]and then the wind blows, that's what's moving this fungus around.
[00:15:50.740]It does overwinter in the leaves,
[00:15:53.340]but it's unknown if it can also overwinter in the soil.
[00:15:58.160]And so there's still a lot of questions that we don't have answers for.
[00:16:02.740]But the good news is, is that because they've had this east of us
[00:16:06.800]for a few years now, they're making a lot of headway on research
[00:16:10.480]and the results are helping us.
[00:16:12.140]I mean, it's about time somebody else gets a disease first, isn't it?
[00:16:15.520]And so all of you were involved in that whole bacterial history
[00:16:20.460]debacle we've had several times now.
[00:16:23.600]And so we're benefiting from their efforts.
[00:16:27.180]So that's more good news.
[00:16:29.060]And so as you move ahead, there's a few things that I want to bring
[00:16:32.860]some attention to, and this makes my head hurt.
[00:16:35.340]This picture, I think it's the scariest picture I've seen in a few years
[00:16:40.800]in the background.
[00:16:42.120]Now, this picture was made in Michigan because they do have some
[00:16:47.120]irrigation in Michigan.
[00:16:48.240]They don't have as much as we do.
[00:16:50.180]In Nebraska, we have more irrigated agricultural acres than any other state
[00:16:55.840]in the country, even California.
[00:16:57.580]And pivot irrigation in particular, because we are putting in moisture
[00:17:02.420]from the top, we're adding a lot of humidity to the canopy.
[00:17:05.940]This fungus is extremely sensitive or dependent, you might say,
[00:17:11.240]on conditions.
[00:17:12.500]And so that moisture is really critical for driving disease.
[00:17:17.600]And so this picture is a picture of a fungus.
[00:17:19.900]This picture, although scary, it does have an important story with it
[00:17:23.740]that I wanted to share with you.
[00:17:25.100]And it's ugly, right?
[00:17:27.680]You can see in the picture, if you look close, you might not there in the back,
[00:17:31.880]but you can see everything under the pivot died first, died early.
[00:17:36.400]It looks like it all senesced.
[00:17:38.780]It even has a gray tint to it because there's so much tar spot in it.
[00:17:42.500]There is tar spot in that non-irrigated corner in some patches there,
[00:17:47.100]but it's not nearly as bad.
[00:17:48.660]The other thing.
[00:17:49.820]You notice when you look at that, you notice it's a windshield wiper pivot,
[00:17:53.820]right? It can't make the full circle.
[00:17:55.280]So that's something else I want to put out that we knew for a long time
[00:18:02.640]before it even got to Nebraska,
[00:18:04.140]that our irrigated fields would be at higher risk for this disease.
[00:18:08.060]And so we,
[00:18:09.820]we knew that for a long time and knowing that it will put us at higher
[00:18:14.880]risk. Now there's a few things here that I,
[00:18:17.940]that I want to point out too.
[00:18:19.540]The field in the background,
[00:18:21.560]as bad as it looks and it killed what was under the pivot early,
[00:18:25.200]that field still yielded 230 bushels under the pivot.
[00:18:29.320]And I know that's considered a crop failure for a lot of you because you're
[00:18:35.260]really good at what you're doing,
[00:18:36.620]but 230 bushels was a lot higher than what I expected after seeing an ugly
[00:18:41.360]picture like that.
[00:18:42.440]And it emphasizes the point that it depends on when a disease develops in a
[00:18:49.000]field.
[00:18:49.320]How much damage it's going to cause.
[00:18:51.240]And so what happened was tar spot came in late in the season in this
[00:18:56.120]location and it, and it flourished there at the end of the season,
[00:18:59.860]much like we see, you know,
[00:19:01.960]we get a lot higher humidity as we get into August and later, right?
[00:19:05.680]We have a lot more dew or cooling off at night a lot more.
[00:19:09.360]Well, that's what happened here. And tar spot blew up on them.
[00:19:13.300]And so most of the grain field stages had a little disease.
[00:19:18.780]And we can sustain a little bit of disease and not have a big impact on
[00:19:22.760]yield. And so that's what happened to them.
[00:19:24.720]And so I wanted to tell that story because it's going to force us to maybe
[00:19:30.340]manage a little bit differently and watch closer what's going on in fields
[00:19:34.240]because the conditions you're seeing is going to probably differ field to
[00:19:38.460]field. And you've seen a lot of that. I forgot to mention too,
[00:19:42.040]as I'm rambling through this, I don't mind taking questions at any point.
[00:19:45.960]Those of you that know me know, I don't, I don't mind you raising your
[00:19:48.240]hand and asking, because I bet somebody else thought of it.
[00:19:50.700]And I know I forget a lot of things that I intend to say.
[00:19:53.520]So please shout it out if you've got a question, but just know,
[00:19:58.120]we also have a student who's now become an extension instructor out in
[00:20:02.460]Dawson, Buffalo and all counties.
[00:20:04.740]And so his name is Talon Muse and he's working on irrigation by tar spot
[00:20:11.280]interactions.
[00:20:11.960]And I'm going to show you some of his research results here in a minute.
[00:20:14.920]And I think you'll find some of that interesting.
[00:20:17.700]We're also looking at and trying to answer questions.
[00:20:22.080]We have so many questions and unknowns.
[00:20:24.460]I'm going to show you data in a minute, fungicide data.
[00:20:28.180]And you're going to see that we've got good products,
[00:20:32.160]but we have a lot of questions about fine tuning, how to use those here.
[00:20:35.580]One of them is about chemigation.
[00:20:37.260]How well does it work compared to aerial application?
[00:20:40.160]And so we have an opportunity.
[00:20:43.900]If anybody wants to be part of the on-farm research network,
[00:20:46.360]we would love to work.
[00:20:47.680]We would love to work with you and help monitor some of that
[00:20:50.680]and collect some data and maybe get some good,
[00:20:52.700]solid research results to prove that.
[00:20:55.300]Coming back to some of Talon's work, though,
[00:20:58.640]there are some observations early,
[00:21:01.680]and we have some really good irrigation engineers now to work with
[00:21:05.240]that I feel like we're making headway on this.
[00:21:08.420]And so one of the first projects that Talon worked on,
[00:21:11.560]you know, it was looking at tar spot under the pivot,
[00:21:15.320]but it was also looking at what we call microclimates,
[00:21:17.660]climate conditions, and that's inside the canopy.
[00:21:21.400]And trying to look at what does irrigation change
[00:21:25.720]that's under the pivot?
[00:21:26.880]And is that going to have an effect on tar spot?
[00:21:29.920]Well, we knew the answer to that already, but why and how?
[00:21:32.920]And so this is the early foundational type of work
[00:21:37.040]that we need to lay the basis before we can move forward
[00:21:40.060]and maybe help make some,
[00:21:41.400]maybe some updated recommendations that will help.
[00:21:44.440]And so one of the things that he did was everywhere you see,
[00:21:47.640]a star, and this of course is not drawn to scale,
[00:21:50.040]but everywhere you see a star
[00:21:51.640]is where we had one of those weather stations set up
[00:21:54.320]and was collecting data.
[00:21:56.060]Now notice there was a weather station in the first span,
[00:22:00.320]closest to the pivot point,
[00:22:01.780]one in the outer span,
[00:22:03.300]and then one in the non-irrigated corner, okay?
[00:22:05.920]And so we had four locations in Eastern Nebraska.
[00:22:10.400]Now those were east of you
[00:22:12.180]because there's more tar spot over in that area.
[00:22:14.880]You're gonna see more, unfortunately,
[00:22:17.620]as we move forward.
[00:22:18.560]But for now, and in 23, when we initiated this,
[00:22:21.620]that's where we started.
[00:22:22.660]Now I know you can't read some of this fine print,
[00:22:26.320]especially those of you back in the back rows back there,
[00:22:28.980]but I'm gonna tell you the parts
[00:22:31.060]that I think matter on here,
[00:22:32.640]the Reader's Digest version, so to speak.
[00:22:34.860]And so looking at these graphs,
[00:22:37.200]we measured a lot of different things
[00:22:39.120]out there in those weather stations.
[00:22:40.740]Temperature was one of them.
[00:22:42.200]Well, tar spot, optimal conditions, temperature,
[00:22:47.600]is about 60 to 70 degrees.
[00:22:49.440]Well, you're probably thinking,
[00:22:51.760]well, it's not ever 60 or 70 out there.
[00:22:54.260]But what about at night?
[00:22:56.380]Our nighttime temperatures and conditions
[00:22:59.800]are sometimes much more favorable
[00:23:01.540]than daytime conditions.
[00:23:02.960]And under the pivot, it turns out.
[00:23:06.080]And so what you can't see,
[00:23:08.240]you know, there's three lines up here.
[00:23:09.660]There's a green, yellow, and blue.
[00:23:11.180]The blue line is showing you the conditions
[00:23:13.640]under the inner span.
[00:23:15.660]The green and yellow,
[00:23:17.580]we're showing you the outer span
[00:23:19.160]and the non-irrigated corner.
[00:23:20.700]Right off the top of the bat,
[00:23:22.920]we saw a huge decrease in temperature.
[00:23:25.280]And that decrease in temperature
[00:23:27.600]was a lot more closer to the pivot point.
[00:23:31.020]And so for instance,
[00:23:32.640]it was seven hours of temperatures
[00:23:35.440]that were lower in that inner span.
[00:23:37.760]And in fact, when it peaked out,
[00:23:40.120]it was 13 degrees cooler in that inner span.
[00:23:43.720]And that held for two hours.
[00:23:47.560]Well, you know, the optimum temperature
[00:23:49.400]is 60, 70 degrees,
[00:23:51.380]but it's still active.
[00:23:53.060]That fungus is still active
[00:23:54.420]outside that range too.
[00:23:56.120]The other thing that's important
[00:23:58.140]is that fungus needs moisture.
[00:24:00.700]It needs high relative humidity
[00:24:02.980]or wet leaves.
[00:24:04.220]And how much of that depends on
[00:24:08.340]how much disease you're going to get later on.
[00:24:10.440]Now, you might be more familiar
[00:24:12.660]with diseases like gray leaf spot.
[00:24:14.680]Well, we've had gray leaf spot for decades
[00:24:17.540]now. You know, really high humidity
[00:24:19.360]is when we tend to see more gray leaf spot,
[00:24:21.400]but that fungus likes warmer conditions.
[00:24:24.020]Temperatures that are, you know,
[00:24:25.880]15, 20 degrees warmer
[00:24:27.460]than what tar spot is most active at.
[00:24:29.880]And so when it's starting to get
[00:24:31.860]humid and muggy
[00:24:33.000]in the canopy, in the field,
[00:24:35.620]that's when gray leaf spot becomes most active.
[00:24:37.960]Usually that's after class one.
[00:24:39.640]And so
[00:24:41.000]you may also know that
[00:24:43.420]gray leaf spot needs 11 or more
[00:24:45.680]hours of 90%
[00:24:47.520]or higher humidity.
[00:24:49.200]So that's a lot.
[00:24:50.960]Well, this fungus, by
[00:24:53.380]comparison, only needs
[00:24:55.600]six or seven hours of
[00:24:57.580]75% or higher
[00:24:59.500]humidity.
[00:24:59.980]So let me say that again. Six or seven
[00:25:03.720]hours of 75%
[00:25:05.680]or higher. That's
[00:25:07.620]not very much.
[00:25:08.660]Especially by comparison to
[00:25:11.680]gray leaf spot. And so
[00:25:13.780]it doesn't take as much
[00:25:15.460]moisture as you might think to dry
[00:25:17.500]the fungus-causing tar spot.
[00:25:19.360]And we're doing it every day
[00:25:21.740]when we have the water.
[00:25:22.760]And so under the pivot, when
[00:25:25.680]you see temperatures drop 13 degrees
[00:25:27.840]for that many hours,
[00:25:29.140]we're really putting it in within that
[00:25:31.600]range of tar spot activity.
[00:25:33.300]On top of that, it doesn't surprise you
[00:25:35.580]that relative humidity, of course, is going to
[00:25:37.480]skyrocket too. And so
[00:25:39.040]in the inner span
[00:25:41.320]under the pivot,
[00:25:42.420]it was 30% higher
[00:25:45.400]for several hours,
[00:25:47.480]but up to 41%
[00:25:49.820]higher.
[00:25:50.460]Tremendous increase in humidity,
[00:25:53.220]no surprise, but it held
[00:25:55.600]there for hours.
[00:25:57.020]Five hours or more,
[00:25:59.320]and at peak, 41% or higher
[00:26:01.560]for three hours.
[00:26:02.600]And that's the inner span versus
[00:26:05.360]the outer span.
[00:26:06.260]So I'm building you up
[00:26:09.460]here. And so conditions
[00:26:11.580]much more favorable toward
[00:26:13.380]the pivot point than out in those outer
[00:26:15.360]spans, at least in 2020
[00:26:17.460]and 2023. And so when you look
[00:26:19.500]at tar spot development, now in
[00:26:21.260]2023, we didn't see as much tar
[00:26:23.360]spot, not like what we saw in 2024.
[00:26:25.420]In 2023,
[00:26:27.000]as Talon was
[00:26:28.620]estimating disease in these locations,
[00:26:31.660]he saw
[00:26:33.200]as early as August 9th,
[00:26:35.420]he saw 40 to 60%
[00:26:37.520]more plants had
[00:26:39.220]tar spot two weeks
[00:26:41.440]earlier in the inner span
[00:26:43.600]versus the outer span.
[00:26:47.440]Did you get that? 40 to
[00:26:49.440]60% more plants. And so
[00:26:51.260]a lot more plants were getting disease earlier,
[00:26:53.240]closer to the pivot point. And by the
[00:26:55.440]end of the season, the inner span
[00:26:57.180]had more disease, that's
[00:26:59.320]the blue bar on the right, than
[00:27:01.380]what the outer span did, or of course
[00:27:03.360]the non-irrigated corner. In the end,
[00:27:05.340]it wasn't statistically significant
[00:27:07.140]that year. And so we're
[00:27:09.240]building the story here that
[00:27:10.760]sometimes we have more
[00:27:13.180]disease closer to the pivot point.
[00:27:15.120]And so at this point, I'm not
[00:27:17.420]going to tell anybody to change
[00:27:19.220]anything you're doing with the pivot.
[00:27:20.560]Right now, that changes my strategy
[00:27:23.200]though. And if I want to know if
[00:27:25.160]disease is starting up, at least to our spot,
[00:27:27.340]I want to go to the pivot point
[00:27:29.200]first and walk around.
[00:27:30.460]And don't do the easy thing we've
[00:27:33.200]done for years and come in from the end roads,
[00:27:35.160]right? That's what we all do, right?
[00:27:37.080]Off the gravel road, you run in. You may
[00:27:39.040]find it. But if you want to see where you
[00:27:41.140]have more activity, I think I'd start at the pivot point.
[00:27:43.320]Okay? That's not
[00:27:45.340]to say that when you first see it that we should
[00:27:47.400]be treating. I've got a story
[00:27:49.260]with that, too.
[00:27:50.080]He repeated some of this in 2024
[00:27:53.500]and a lot of other work,
[00:27:55.260]too. And so
[00:27:56.920]generally speaking, 2024,
[00:27:59.140]you know, a lot different year. A lot more moisture
[00:28:01.320]up front. Then the faucet
[00:28:03.300]got shut off, basically, and we irrigated
[00:28:05.560]the rest of the season.
[00:28:06.780]He still saw the same trend
[00:28:09.340]and that's graphed out a little bit differently
[00:28:11.220]on the left. And so the further
[00:28:13.060]away from the pivot point he was,
[00:28:15.140]the less disease there
[00:28:17.380]is, but it didn't matter statistically.
[00:28:19.660]And that graph on the
[00:28:21.460]right-hand side, as long as it was getting
[00:28:23.280]water, it didn't even matter because
[00:28:25.460]we were probably watering so
[00:28:27.360]much in the last half.
[00:28:28.600]So, oh, is something happening over there?
[00:28:31.320]Oh,
[00:28:33.380]what happened? I can't
[00:28:35.480]see that one. Sorry. Thank you
[00:28:37.340]for fixing it. Please do that.
[00:28:38.800]Am I standing in front
[00:28:41.400]of this one too? I'm trying to get away from this.
[00:28:42.980]So do you understand what I'm
[00:28:45.340]saying? Around the pivot point, you might see
[00:28:47.360]more, but you may not every year.
[00:28:49.520]Okay? So we
[00:28:51.420]still have a lot to learn about that.
[00:28:53.140]Thank you for fixing that. It didn't
[00:28:55.400]do any good if you can't see.
[00:28:56.520]So moving forward, any
[00:28:59.320]questions about where we've gone so far?
[00:29:01.620]I'm going to dig a little bit
[00:29:03.420]deeper.
[00:29:03.700]As you can imagine,
[00:29:07.340]we don't have a lot of fungicide
[00:29:09.680]data. I do a little bit now.
[00:29:11.600]But the best data are coming
[00:29:13.600]out of places like Indiana
[00:29:15.380]where they've been working on this the most
[00:29:17.340]and my counterpart, Darcy
[00:29:19.300]Talenko is the plant pathologist over there
[00:29:21.500]and I'm really grateful.
[00:29:23.280]We all work really well together
[00:29:25.200]across these Corn Belt states. We all
[00:29:27.300]share data back and forth and so
[00:29:29.440]she shared with us
[00:29:30.640]a summary of some of
[00:29:33.340]that early work that they've done on
[00:29:35.220]tar spot and this is the best
[00:29:37.300]we've got so far and so
[00:29:39.240]I want to acknowledge their efforts and she's
[00:29:41.420]coordinating all of our tar spot
[00:29:43.140]trials across the country and so
[00:29:45.240]our data feed back into a big mass
[00:29:47.320]set and so it's much
[00:29:49.360]more powerful than just having you know
[00:29:51.400]a year here there or wherever
[00:29:53.300]most of our works at Clay Center
[00:29:55.040]we do work up at Northeast Nebraska
[00:29:57.560]at Haskell Ag Lab or at
[00:29:59.160]NREC over by Mead too and elsewhere
[00:30:01.260]but we still don't have the
[00:30:03.280]pressure to have the type
[00:30:05.300]of research we need to really understand
[00:30:07.280]what's going on and one of those
[00:30:09.400]is the first step to figure out
[00:30:11.360]which products are going to work the best
[00:30:13.160]this is not new news to
[00:30:15.360]most of you the good part
[00:30:17.300]is that we do have products that work
[00:30:19.480]if you need them
[00:30:20.360]my first solution is always
[00:30:23.340]to tell you now that tar spots moved
[00:30:25.280]into your area I would start
[00:30:27.240]selecting hybrids that have good ratings
[00:30:29.380]for tar spot development
[00:30:31.520]we can see
[00:30:33.360]a significant drop in
[00:30:34.660]disease pressure if you select
[00:30:37.600]hybrids that have good disease ratings
[00:30:39.480]sometimes
[00:30:41.040]though we still might need fungicides
[00:30:43.640]to manage that
[00:30:45.080]and so here's some
[00:30:47.280]good news some of the products we're
[00:30:49.580]already using that are commercially available
[00:30:51.540]do a great job
[00:30:52.700]and so in their earliest work up here
[00:30:55.720]they showed really quickly
[00:30:57.580]and if you look on the graph on the left hand
[00:30:59.640]side that gray bar is your non-treated
[00:31:01.660]control it did not get a fungicide
[00:31:03.480]the bars after it
[00:31:05.660]are showing you different products that were
[00:31:07.500]applied one time I think that was about
[00:31:09.460]an hour one and this is
[00:31:11.460]across five different environments in
[00:31:13.600]Illinois, Indiana, Michigan, Wisconsin
[00:31:15.660]and Canada.
[00:31:17.260]Ontario and so
[00:31:19.180]this is disease data
[00:31:21.420]so you want the smallest bar you can
[00:31:23.640]to show the least disease
[00:31:25.620]so on the right
[00:31:27.580]hand side of the graph those are the products
[00:31:29.440]that did the best job
[00:31:30.860]all of them did a good job of reducing
[00:31:33.700]disease but some just did a better job
[00:31:35.780]the products that tend
[00:31:37.500]to do a better job are the ones that are
[00:31:39.440]the more complicated ones right
[00:31:41.320]that have mixed premixes
[00:31:43.240]of different active ingredients
[00:31:45.400]from multiple fungicide
[00:31:47.240]classes
[00:31:47.820]now back to your
[00:31:50.560]pesticide training and recertification
[00:31:53.000]you probably hear all about fungicide
[00:31:54.980]classes well right now
[00:31:57.000]in corn and soybean we are
[00:31:59.080]primarily using fungicides from
[00:32:00.980]only three different classes
[00:32:03.180]three seven and
[00:32:04.920]eleven most of those
[00:32:07.280]are eleven three
[00:32:09.180]and eleven starting with usually
[00:32:11.160]you know you've heard of
[00:32:12.720]the strobilurins you've heard of the
[00:32:15.020]triazoles probably that's what most of
[00:32:17.220]them are well now we've added a group seven
[00:32:19.100]so we've got some three way products
[00:32:21.180]the two and three
[00:32:23.400]way mixes are the
[00:32:25.140]ones that have been doing the best job
[00:32:27.060]that's no surprise
[00:32:28.440]and so your examples
[00:32:31.160]here on the right
[00:32:32.180]you've got Dilaro Complete, Beltima
[00:32:35.080]and Revitec well there are
[00:32:37.020]others here you know Approach, Prima, Headline
[00:32:39.260]SC
[00:32:40.240]they were not statistically different
[00:32:42.880]so all of those did a good job
[00:32:44.740]great okay we kind of already knew
[00:32:47.200]that
[00:32:47.440]if you have a question about using
[00:32:50.840]and mixing generics to represent
[00:32:53.060]some of those same active ingredients or
[00:32:54.980]classes although we don't have
[00:32:57.020]data on that yet we will in
[00:32:58.820]2025 willing
[00:33:00.420]we expect similar
[00:33:03.000]benefits from that okay
[00:33:04.840]be sure and watch the label restrictions
[00:33:07.220]though some of those products cannot
[00:33:08.980]be applied more than twice
[00:33:11.710]season or those active ingredients came and some of the different products have the same
[00:33:17.030]classes in them okay because again we're only working with those three so that's great when do
[00:33:23.530]we make those applications and so i'm going to show you a little bit of that but if you want to
[00:33:27.510]read a summary of what all these university trials are showing you can go to the crop protection
[00:33:34.090]network that's all free okay and there's a there's a big table and there's ratings by disease up here
[00:33:41.390]listed on the top that tells you what those ratings are for each of those products if you have your
[00:33:46.730]nebraska pesticide applicators license and you have the big spiral bound we call it the weed guide
[00:33:52.390]or you have a thumb drive with that it's already in there okay it's just a one year behind because
[00:33:58.470]this table just came out for 2025 but the 2024 version was already in your book okay because i
[00:34:05.790]take it from there and put it in that book every year okay so you've got it at your fingertips
[00:34:11.070]i think it might be easier to find if you just google it though the crop protection network
[00:34:15.290]and corn fungicide efficacy table okay if you can't find it tweet at me or something and i'll
[00:34:21.170]help you okay it's easy so you can go there and see what the ratings are but the questions are
[00:34:27.510]when do we make that application and it does get more complicated then
[00:34:31.210]and so if you called me and asked me i'd ask you about seven different questions honestly
[00:34:37.990]because there's a lot of factors that we want to
[00:34:40.750]take into account about fungicide application decisions and so some of the next work that they
[00:34:47.590]did at purdue this is a three-year study they looked at timing and so i hope you can see what
[00:34:54.610]this graph says but this is another disease graph non-treated control is over here on the left again
[00:35:00.130]and then your timings from left to right v67891011 vtr1 blister milk dough dent and then a dual
[00:35:10.430]application on the far right side i bet i'm in front of you guys too maybe i'll go back over here
[00:35:16.990]now so you can see that because i want you to watch the graph because when i hit the button
[00:35:21.570]again you're gonna see a red bar come up on there that is how much disease was there the day they
[00:35:29.270]sprayed okay and so you can see there was already disease all the way as early as v67 in those little
[00:35:38.550]plants
[00:35:39.070]and that is a possibility for us too in our irrigated environment but what i really want
[00:35:46.750]to show you is it didn't really do much and it stayed really low on the plant it stayed very
[00:35:53.650]minor and so over here this is the percent of leaf area covered by disease okay and so very very low
[00:36:03.050]a trace to almost nothing and you didn't start to see it change
[00:36:08.990]until around vtr1 and it was by the time we got to blister it was up to about a half percent
[00:36:15.970]and so what she's doing is she was measuring after we had the ear leaf come out they were
[00:36:22.430]only estimating how much disease was on the ear leaf that's it and a lot of our data you see we
[00:36:28.590]do canopy wide we're estimating across the whole canopy and that's a lot harder to teach somebody
[00:36:33.970]but just looking on the ear leaf this is something we can teach anybody and
[00:36:38.910]so disease didn't really start to move until around around blister stage and then by the
[00:36:45.670]milk stage it jumped way up to almost four percent and then you saw it all the way over
[00:36:51.410]here about dose stage it got up to about just over six percent by then and so uh by by then we had
[00:37:00.450]all the way up to about seven percent and so there's two points here one of them is that
[00:37:06.470]you can see by looking at this
[00:37:08.830]that those treatments made toward the middle of the season from vt to about the milk stage
[00:37:15.490]kept disease the lowest and they didn't spray necessarily when they first found disease
[00:37:21.650]it was already starting to move up and they still in spite of that got good controlling okay
[00:37:29.010]and so that was good news and if any of you've been following some of the conversations on
[00:37:35.810]social media like around the crop protection network
[00:37:38.750]you saw there was a lot of discussion about comments that were made from the crop protection
[00:37:45.890]network about Darcy had said she did not believe that we could let disease get above five percent
[00:37:54.830]that once we got past five percent it was too late to spray that's five percent on the
[00:37:59.990]ear leaf well that turned out to be a pretty inflammatory statement okay and so if you
[00:38:06.470]were watching social media and most of that was on
[00:38:08.670]it's not twitter on x you might have seen some of that well this is the data set where
[00:38:13.890]that came from and so note between about vtr one up to about milk we still had disease
[00:38:21.110]less than four percent once it got up above six percent is where things went awry the
[00:38:26.990]green bars show you the economic return and so the dollars per acre over on the right
[00:38:32.950]hand side and so when you pencil all of that out including the cost of application and
[00:38:38.590]supply it's that same window except maybe a little bit wider so we go from about vtr
[00:38:45.430]one up through the dough stage and so they still worked up until that point and so that's
[00:38:53.350]about six percent there where they sprayed so five or six percent's a tipping point when
[00:38:59.030]it gets to the ear leaf but there's a lot of other questions and things we would want
[00:39:02.830]to know to feel more confident about whether or not that's going to give you the economic
[00:39:07.610]return that you're looking for
[00:39:08.510]and so that's where some of those conversations stemmed from okay so what's your next question
[00:39:15.990]what is i don't know what five percent looks like right that that can be tricky right well
[00:39:21.210]let's look at that there's another tool also on the crop protection network that i think
[00:39:26.530]you might find some value in and so here's the first one so everybody see that leaf got
[00:39:32.210]some black spots on it not too bad right now let's pretend that
[00:39:38.430]it's the ear leaf and if you estimate you can have a number in your head or if you're
[00:39:42.830]brave go ahead and yell it out what do you think the percent coverage of that leaf is
[00:39:47.670]okay ready set go two percent are you surprised i see some giggles we always get some giggles
[00:40:00.510]right here did you estimate higher or lower higher yes
[00:40:08.350]yeah and so that's normal that is normal for us to overestimate disease severity now
[00:40:18.130]the good news about that is if you know that your inclination is going to be to overestimate
[00:40:23.850]you can temper that a little bit the second thing i would recommend is don't just look
[00:40:28.950]at the black spots i would look at how much green leaf tissue is showing because to me
[00:40:35.150]that helped that helped me quite a bit and these are the things that we teach
[00:40:38.270]students when we go out in the field and how to estimate okay let's let's play this
[00:40:43.390]another round oh that one looks worse doesn't it anybody see anything that looked like that
[00:40:48.190]last year i hope not got your number in your head you're close
[00:40:56.070]and yeah that one's 10. this is computer generated don't argue with me about it that's the computer
[00:41:03.790]that did that and so that's 10
[00:41:08.190]okay last one ready
[00:41:10.570]got your number we gotta do this fast when you're walking through the field right ready
[00:41:18.070]bye are you kind of getting the hang of it is this making more sense now helping us to
[00:41:26.030]make that so this is just an exercise in trying to trying to train your eye and so five percent
[00:41:35.470]there on the right hand side
[00:41:38.110]this one that's about what you know the the cutoff is on the ear leaf or fungicide application
[00:41:44.790]is what Darcy was saying looking at all those data that they collected and I only showed you
[00:41:50.030]about 20 percent of it so far okay I uh I'm going to hit the highlights for you and so that's where
[00:41:57.230]some of that um those conclusions came from so if you want if you want to look at this yourself
[00:42:02.930]again it's free the crop protection network is a is a work of
[00:42:08.030]about 13 different universities including ours and all of our specialists and so I have a lot
[00:42:12.890]of confidence in what goes up there I hope you don't need to but I think we'll have folks that
[00:42:21.070]will eventually get enough tar spot that you might think about applying twice fungicide twice
[00:42:27.310]we're really in this part of the state on the front edge of where that is and just beginning
[00:42:34.730]to develop more and so east
[00:42:37.950]of you there's more disease developing under the pivot especially in some of those fields
[00:42:42.830]in states east of there there's a lot more disease and it's not that we have that much
[00:42:49.550]disease every year some years we will and so in some cases I think some people might end up
[00:42:56.830]spraying twice and so I've already been getting a lot of questions about it and people maybe
[00:43:02.110]already sprayed twice but they wondered okay I know what products work do I spray that for
[00:43:07.870]first and then that's what I spray the second time or do I spray this one first and the other
[00:43:12.890]one the second time or do I do them in a different order and so you can see there's a lot of different
[00:43:17.050]questions coming up about that and so thankfully again we have some Purdue data to support that if
[00:43:23.410]you need to spray twice and so look at the different colored bars up here on this table and let's lay
[00:43:30.670]this out and so single applications of one of those products are in the top of that so the non-treated
[00:43:37.790]on the top then you've got Veltema, Approach Prima, Mirrorless Neo, Dilauro Complete and Headline Amp.
[00:43:44.590]Now in the blue bars in the middle that's the same products applied at VTR1 right at Tassel
[00:43:53.210]you know full emergence to and then three weeks later that's 3WAT that's three weeks after
[00:44:00.010]treatment then they sprayed Headline Amp. The reason that was three weeks is because most of these
[00:44:07.710]products even the ones that work really well still provide only a narrow window of protection
[00:44:13.950]of about three weeks at their best okay and so if you needed a second one you would want to do
[00:44:21.870]it at the end of that window of time because that's when the plants become vulnerable again
[00:44:26.070]and so Headline Amp was sprayed the second time now if you flip that and look at the
[00:44:32.850]bottom section they started with Headline Amp and then three weeks later followed up
[00:44:37.630]with one of those other products on top okay does that make sense okay let's keep going
[00:44:44.570]so there's a couple of things about this graph that I there are more disclaimers than anything
[00:44:50.510]else I dislike the dates and the crop stages because they do not match what you and I see
[00:44:57.510]here in Nebraska and as I click through this you're going to see disease developing in each
[00:45:04.150]of these different uh each of these different treatment combinations
[00:45:07.550]that are listed down here at the bottom and I know some of you won't be able to read that but
[00:45:11.570]I'm going to read you the ones that it did well at the end okay and so as I click through here
[00:45:16.370]if some of you can see the graph uh legend on the right I would disregard that respectfully
[00:45:23.230]because what they're going to show you is going to go all the way up through from
[00:45:27.390]August up through the middle of October when you would have already been picking that corn
[00:45:31.770]okay so let's go and so in the beginning you saw a little bit of disease
[00:45:37.470]showing up and then by early September you know what we were getting a lot more disease
[00:45:46.370]in that non-treated control it made everything look like it was working really well okay and so
[00:45:52.830]then by the middle of October you saw that disease did ramp up but some of those treatments
[00:46:01.990]held up disease all the way through the middle of October some of them did a really good job
[00:46:07.390]and definitely better than other treatment combinations or sequences and so the blue bars
[00:46:14.030]in the middle show you a lot lower disease in some of these and then a couple of these bars over here
[00:46:20.430]in that I think red over on the right hand side and so if you look at the ones that statistically
[00:46:26.170]or that means consistently did the best across the replications the ones that did the best were
[00:46:31.770]in those blue bars and also a couple in that early one and so you know the the
[00:46:37.310]Veltima, Approach Prima, Miravis Neo, Delorio Complete followed by Headline Ant and then this
[00:46:43.610]other one over here Headline Ant followed by Veltima and then Headline Ant followed by Approach
[00:46:48.650]Prima. Economically those are the ones that floated to the top and so honestly any other combination
[00:46:55.610]from the middle I would feel comfortable with especially these first three and the first two
[00:47:00.330]from this other graph and the one overall that had the best economic return was the Headline
[00:47:07.230]Ant followed by Veltema and so in the in the end I think several of these would have worked fine
[00:47:15.050]that's what their data showed. I'm not promoting two applications of fungicide I'm not even saying
[00:47:21.650]everybody needs to spray once but we we probably are going to have to be a little bit more diligent
[00:47:27.030]and scouting a little bit how harder to know what's going on out there and it will vary from
[00:47:32.410]field to field okay. So before I move on
[00:47:37.150]I know you're all chewing on a lot of this data maybe even disagree with some of it
[00:47:41.270]let's hear what you have to say I'd love to hear your observations too.
[00:47:44.870]They might be asleep.
[00:47:49.470]How about I'll talk about this one last thing and maybe something will have floated in the
[00:47:56.630]and so there's a couple of things I wanted to share with you too
[00:48:02.390]about I think Mariah you said let's talk about anything that's new.
[00:48:07.070]I hate to say the word new disease. You've all been through this with me and back in 2016 I think
[00:48:13.010]with bacterial leaf streak but we did see something last year that we had not seen in Nebraska before
[00:48:19.210]and I'm guessing you probably saw some of the news and in some of the trade magazines that
[00:48:24.670]there were some new things going on south of us and I wanted to talk about that a little bit
[00:48:29.350]mainly let you know we know we saw it too. Here's why we weren't as worried about it.
[00:48:36.990]Up here and so if I ever hear of corn stunt probably there's been there's been some talk
[00:48:45.450]about it especially among the seed industry. This is not a new disease folks corn stunt's
[00:48:52.030]been around for decades apparently not a common problem in the United States but it has occurred
[00:48:59.610]decades ago sporadically. South Texas, Southern California, a few other states in the deep south
[00:49:06.910]sporadically. Now this is caused by one of four different pathogens and this is good this part's
[00:49:16.110]going to get annoying okay. Spiroplasma is the most common one and you might not have heard of
[00:49:22.410]a spiroplasma before because we don't have any other important diseases in our crops
[00:49:26.590]caused by a spiroplasma. There's also a phytoplasma. Well spiroplasmas and phytoplasmas
[00:49:33.470]are kind of looped under bacteria. There's
[00:49:36.830]a similar, a lot smaller, nobody cares, right? We also have a couple of viruses that can
[00:49:42.670]cause corn stunt. Three of these pathogens have been confirmed in the United States.
[00:49:49.170]One of them has not. And so all of them are vectored by the corn leaf hopper, which until
[00:49:58.850]2024 had not been confirmed in Nebraska. And so we don't watch for it too much or think
[00:50:06.750]about it. But remember what we talked about at the very beginning, hurricane barrel.
[00:50:12.330]Hurricane barrel is blamed for a lot of bad things this year. One of them was pushing
[00:50:18.770]the corn leaf hopper further north in addition to all that southern rust. Okay. And so we
[00:50:24.690]believe what happened is we had populations of the leaf hopper move further north and
[00:50:31.030]it was first reported in Oklahoma. And they were also seeing some
[00:50:36.670]pretty scary symptoms that turned out to test positive
[00:50:42.310]for corn stunt spiroplasma. That's the most common of the four pathogens. That's the one
[00:50:48.750]that causes most of corn stunt. The type of symptoms they were seeing, a lot of
[00:50:54.190]purple leaves, stunted plants. How many things can you think of that cause a plant to turn
[00:51:00.710]purple, a corn plant? You know, there's a half a dozen things, right? If you rip off the ear,
[00:51:06.590]at the right time, the plant will turn purple in the next few weeks because it doesn't have a place
[00:51:10.590]to put all those sugars. It can't put them in the ear, and so they deposit them in the leaves and
[00:51:16.150]the stalk. There's other diseases that can do that. Damage, when we nick it with the brush hog or
[00:51:23.430]something while we're mowing alongside, and even some hybrids tend to have more of the purple pigment
[00:51:29.510]anthocyanins in them, and so by the time senescence comes, a lot of them purple up as they're starting
[00:51:36.510]to dry down, okay, and so you probably saw a lot of purpling last year, and you're already thinking
[00:51:42.090]in your head, oh gosh, I think I saw that. Maybe you did, maybe you didn't, okay. I think it was
[00:51:48.110]probably more widespread than we knew, and so you might have noticed earlier, I forgot to point out
[00:51:53.790]that the tar spot map was not filled in all the way. I kind of abandoned tar spot and went looking
[00:52:00.270]for stunt, and so unfortunately did find some,
[00:52:06.430]and so I wanted to show you that, and the map that I'm showing you right now is incomplete.
[00:52:12.350]It's mainly showing you the 10 new states where corn stunt was confirmed in samples, as well as
[00:52:20.910]the leaf hopper. We confirmed both in Nebraska this past year, and so it wasn't until right at the end
[00:52:27.870]of the season that we got word out of Kansas that they had confirmed it in, catch this, 26 counties from
[00:52:36.350]eastern to western Kansas, and so we were talking during all this. They didn't know how many of those
[00:52:42.030]samples they collected through a positive in the lab, and it was 26 counties. My bet is that if we'd
[00:52:50.670]have known in time to look earlier, we would have found a lot more corn stunt from eastern to western
[00:52:55.730]Nebraska, but not that I think it was causing damage, because I think what we did see moved in
[00:53:02.130]so late, it wouldn't have caused the damage that what they saw down in Oklahoma,
[00:53:06.270]in southern Kansas. In Nebraska, I spent a day with a crop consultant in Jefferson and Gage
[00:53:13.750]County, down here in the corner, the reason we focused down there was because one of the first
[00:53:18.650]places they found and reported it in Kansas was in Manhattan, and many of you know that's up in
[00:53:23.590]the northeast corner, and so we were looking straight north, straight north of there,
[00:53:28.650]and so during that day, I think we visited nine fields, I collected samples
[00:53:36.190]across the sultan already marked some of them for us, and two of those samples through positives,
[00:53:43.290]and so I can't even tell you which ones we saw because all the purple looked the same to me,
[00:53:50.730]I can't tell you some of those on how to tell them different, and so later we also got a third
[00:53:57.570]sample from up here in Burke County in the northeast, but eventually they threw, they had
[00:54:03.650]a positive sample all the way up in Brookings, South Dakota, and so we were able to get a
[00:54:06.110]one over in Minnesota, some in Wisconsin, then even up into New York State, and one in Indiana,
[00:54:12.010]so you don't find things until you know what to look for, right, and so there was probably more
[00:54:18.070]out there. The thing is, we're not terribly concerned at this point because there's really
[00:54:25.350]no evidence that this leafhopper can overwinter here, and so that's one question we have. There's
[00:54:36.030]a lot of us to monitor. I'll tell you, though, as new as, what was it, three weeks ago, there was
[00:54:41.890]still live leafhoppers found in southwest Kansas, and so they're watching that pretty closely,
[00:54:48.790]but the things that also we don't know is once the bacteria, the bacteria, the spiroplasma were
[00:54:54.870]in the plants, is it possible some of our native leafhoppers or other insects picked it up?
[00:54:59.990]We don't know that, and so in any case, although we're not terribly concerned, if you see some
[00:55:06.010]unexpected purpling during the season and not on a plant you've pulled the air off of,
[00:55:11.010]you know what, let us, let us know. We'll go get a sample from you, and we'll test that in the
[00:55:15.190]diagnostic clinic, but this is something we'll be watching, and we did get funding to do our own
[00:55:21.630]insect trap survey, and so if you're watching for symptoms or we're catching bugs, then we'll be on
[00:55:27.310]the lookout for it, but at this point, I don't have any reason to think that this is going to
[00:55:31.490]be a common problem for us, but we'll, we'll stay on top of it, and
[00:55:35.930]anything you find, we're happy to test, so that kind of went over the amount of time I think we
[00:55:42.190]agreed on, Mariah, but that kind of summarized all the stuff I thought I wanted to share with you.
[00:55:47.310]I'm happy to answer questions or show you more graphs and pictures and things, but hopefully
[00:55:54.050]you don't need that information, but I think over time, we will see tar spot increase as we build up
[00:56:01.610]that inoculum base, and it's going to force us to learn how to manage it,
[00:56:05.830]so start with the hybrid, and if you need a fungicide, we do have some data to support
[00:56:11.390]some of that, so any questions? Some of you have heard this multiple times now,
[00:56:17.170]and maybe you've had more time to think through it.
[00:56:19.430]While you're thinking that, thank you all so much for coming, and I saw your hand up.
[00:56:35.730]So, question about, you know, hitting the 5% tar spot. I'm going to say, I hope I never
[00:56:49.050]use the word threshold, because you shouldn't ever hear a plant pathologist say we've got
[00:56:55.610]thresholds, and part of that's because of how many other factors influence disease development.
[00:57:00.330]You know, if you and I talked in the season, and you're trying, you know, you're getting close
[00:57:05.630]to five percent, you're getting about four percent trying to decide if you should do it or not.
[00:57:09.530]One thing I'll ask is how much disease did you have in the past, and that can be a good predictor
[00:57:15.950]of what might happen in the future. You know, we would also look at weather factors. You know,
[00:57:20.770]if it's going to be 100 degrees every day, maybe it won't be as favorable, but I still think under
[00:57:27.230]the pivot there's a chance of seeing some, but maybe it would slow it down. Other things I would
[00:57:32.370]ask about, maybe do we know anything about the hybrid, and you know, what
[00:57:35.530]the ratings are for that, how it's performed in other areas of the country with tar spot?
[00:57:39.730]Those are kind of some of the questions that I would ask. The other thing, too, is how much
[00:57:48.590]disease is in the rivers below that. One of the things that's been really deceptive is,
[00:57:53.790]you know, it might look like tar spot suddenly blows up, but it really doesn't. In the field,
[00:58:01.250]it's common for tar spot to take 15 to 21 days,
[00:58:05.430]by the time that little spore lands, and then it germinates, and then it infects,
[00:58:10.430]and it grows and turns into that black spot that you and I can see up to up to 21 days. And so
[00:58:17.730]honestly, it's moving pretty slow, but there's a lot more of it in those spores. And so that's
[00:58:25.130]part of the reason why if you've already hit 5% on the ear leaf, there's a lot more disease
[00:58:31.830]around it that you and I can't see yet, if that makes sense.
[00:58:35.330]A lot like gray leaf spot, because you remember gray leaf spot starts on those lower leaves
[00:58:40.050]and it marches up the plant.
[00:58:41.850]So if it's two leaves below the ear leaf, you can't see it, but it's infected the ear
[00:58:47.550]leaf.
[00:58:48.550]And so that was always a pretty good measure of what it's doing.
[00:58:52.050]Does that kind of answer your question in a lot more words than you asked before?
[00:58:59.210]Thank you.
[00:59:00.210]Anybody else?
[00:59:01.210]Is there anoculum, you know, over the years that you've controlled gray leaf?
[00:59:05.230]Does that have a tendency to be on the same tar spot?
[00:59:08.510]You're trying to control a little earlier than what you should, you'll have less.
[00:59:14.350]As far as fungicide timing?
[00:59:15.690]No, just fungicide in general over the years.
[00:59:18.690]You have less disease out there.
[00:59:21.470]Oh.
[00:59:22.470]Well, you'll have less disease, or is it more to deal with the environment?
[00:59:27.850]A little of both, maybe.
[00:59:29.450]My bet would be, though, even when we've done a really good job controlling disease through
[00:59:35.130]the grain fill stages, once we get past those critical stages, the plants can get increasingly
[00:59:42.210]susceptible as they put all their resources into grain fill.
[00:59:46.370]We see that flush at the end where it looked really bad in some of the fields, like what
[00:59:51.350]it did in that Michigan field.
[00:59:54.210]But it still yielded better than you expected, but all that would have overwintered.
[01:00:00.490]Now, the next part of that is, I didn't mention.
[01:00:05.030]I've got a lot of questions about crop rotation, tillage, other ways that we might be able
[01:00:10.370]to manage this.
[01:00:11.990]In states east of us, that has not been very effective against tar spot.
[01:00:18.530]And we don't know the answers yet about whether it's also overwintering in the soil.
[01:00:24.290]That could explain why, you know, tillage and rotation aren't very effective.
[01:00:28.890]But it's also an airborne disease.
[01:00:30.810]It's moving really easily.
[01:00:34.530]Those are a couple of things.
[01:00:36.030]Plus, we believe there are other species of grasses that are susceptible, too.
[01:00:40.670]And so if you see black spots, and there's lots of, you know, in the brown grasses and
[01:00:44.570]stuff in the fence line and in the ditches, we're seeing other diseases.
[01:00:48.650]But now we think we've seen tar spot.
[01:00:50.530]And so our counterparts up at Minnesota are actually doing that work.
[01:00:53.830]And so we've sent them samples from Nebraska.
[01:00:56.510]And we'll send them more if you find something.
[01:00:58.930]And so coming back to your question, then.
[01:01:03.090]With the four or five.
[01:01:04.030]I'm mainly concerned about protecting during grain fill.
[01:01:11.090]We always think it's a good idea to rotate and try to get out of that to let some of
[01:01:15.430]that break down.
[01:01:16.430]But at this point, it's not very effective.
[01:01:19.170]And so it might help with some of the other disease pressure, though.
[01:01:22.830]And so spraying fungicides, I don't think necessarily prevents the amount of inoculum
[01:01:28.110]going into overwintering, though.
[01:01:31.610]I don't think that was the reason.
[01:01:33.530]It's like gray leaf, we control it enough where it's not really, it hasn't really cleared
[01:01:39.910]up as much as it could have by controlling it every year.
[01:01:46.590]I would argue that might be more of our hybrids.
[01:01:49.490]I think we've eliminated hybrids that maybe are a little weaker on gray leaf spot.
[01:01:54.850]Maybe we're not seeing as much of it, because we definitely had enough moisture this past
[01:01:59.150]year for gray leaf spot, right?
[01:02:01.490]We weren't as warm.
[01:02:03.030]Most places in Nebraska did not hit 100 degrees last year.
[01:02:05.990]We were a touch cooler, maybe more on the tar spot side, but I think in general across
[01:02:13.070]the Midwest, we're not seeing as much gray leaf spot.
[01:02:16.170]I credit the seed companies for that, and eventually I think we'll get there for tar
[01:02:20.710]spot too.
[01:02:22.150]One thing I'll tell you about working with tar spot, it's a real difficult disease for
[01:02:28.310]our seed companies to work with.
[01:02:30.970]All the other examples of diseases.
[01:02:32.530]We've talked about including bacterial leaf streak, Goss's wilt.
[01:02:37.030]My lab and other labs around the country literally grow buckets of these bacteria and fungi,
[01:02:43.770]and we sell them to seed companies to use to inoculate intentionally their disease
[01:02:49.170]nurseries and that's so they can collect data and get an idea of how well their hybrids
[01:02:53.630]are going to work.
[01:02:55.290]And so it turns out, though, the fungus causing tar spot is not one we can grow on petri dishes.
[01:03:02.030]And that's oversimplifying it a little bit, but I can't grow buckets of it and help seed
[01:03:06.690]companies work with it.
[01:03:09.330]And that's really slowed down the process.
[01:03:11.990]And so in the early years of tar spot, seed companies actually went out and gathered up
[01:03:17.050]pickups full of infected leaves with the black spots on them and hauled them to the disease
[01:03:22.970]nursery and scattered them around, watered it and made disease happen that way.
[01:03:27.870]But that sounds simple, but it's actually slowed down.
[01:03:31.850]How much, how many ratings we've got, plus there's just not a whole lot of resistance
[01:03:36.830]out there to work with, but they do matter.
[01:03:39.970]The ones that do have some resistance are a lot different.
[01:03:43.010]That was a whole 10 minute thing you didn't intend to get started on, wasn't it?
[01:03:49.350]Sorry about that.
[01:03:50.350]Anybody else?
[01:03:51.350]Yeah.
[01:03:52.350]On application, do you recommend it by error, or is there something I can put in there?
[01:03:58.210]That's a good question.
[01:03:59.210]I was afraid you were going to ask me that.
[01:04:00.910]So if you couldn't hear.
[01:04:01.670]Are we recommending aerial application or chemigation or some other route?
[01:04:08.190]I don't have data to argue either way.
[01:04:11.550]I've had anecdotal evidence where people have shown me and said, oh, yeah, you know, I chemigated
[01:04:17.190]this on and it did really well.
[01:04:19.430]Oh, wait, I put that on by a drone and it looks like garbage.
[01:04:23.670]So I know the fungicides work.
[01:04:26.670]So if it didn't work, I more blame the quality of the application.
[01:04:31.490]One thing that's been evident to us is it is critical that we get really good coverage
[01:04:37.810]to control this disease.
[01:04:41.210]We've got some other anecdotal evidence.
[01:04:42.930]I wish I had more data on, but I feel like if you're going to chemigate on, as long as
[01:04:49.250]you do a really good job chemigating, for example, be sure and calibrate with fungicide
[01:04:55.930]and not with water.
[01:04:57.690]That was a mistake we made, but you can learn from our mistake.
[01:05:01.310]We calibrated with water.
[01:05:04.230]What happens when you chemigate, you don't put on as much as what you intended to, and
[01:05:08.770]then it didn't work as well.
[01:05:10.670]We still had some benefits, but it wasn't enough.
[01:05:12.930]We put on half the product we meant to.
[01:05:16.250]I think drones can do a good job.
[01:05:18.130]We've seen evidence of it, but then we've seen evidence where some of them didn't work,
[01:05:22.410]and we had a lot of disease in between the swaths.
[01:05:27.430]Coverage is critical in getting it down in the canopy, no matter how we're going to do
[01:05:31.130]it.
[01:05:32.130]So I don't have a clear answer.
[01:05:33.810]I just know it's really important, and that's why we want to conduct more on-farm research
[01:05:37.410]trials.
[01:05:38.410]So if anybody wants to try it, let me know.
[01:05:41.610]Good question.
[01:05:43.230]I hope I'll have an answer in a year or two.
[01:05:48.070]Anybody else?
[01:05:50.250]I'll hang out with you for a little bit, too, if you're shy and don't want to ask, but thank
[01:05:53.930]you all so very much for coming out on this day.
[01:05:56.130]Hopefully the roads are nicer for you, and I'll look forward to talking to you.
[01:06:00.950]Hopefully in a cornfield, that will be nicer this year.
[01:06:04.370]So thank you all so much, and thank you for the Extension Board and Mariah and all the
[01:06:08.670]sponsors.
[01:06:09.670]Remember, you've got Extension resources here year-round, and so you've got -- there you
[01:06:15.210]went.
[01:06:16.210]Steve's right there in the back.
[01:06:17.210]He's a fantastic resource, and I appreciate getting to work with him and all of you.
[01:06:21.330]Thank you all so much.

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