Episode Transcript
[00:00:00] Speaker A: Welcome to Missouri Corn Talk, your go to weekly agriculture podcast, delivering fast, reliable updates on market development efforts, ethanol demand, and the issues shaping today's corn industry. I'm your host, David Geiger. As corn moves through some of its most critical growth stages, many growers are asking the same question. Is it time to spray a fungicide, or is it better to wait? Diseases like tar spot and southern rust have become familiar names across Missouri, but knowing when they pose a threat can make all the difference for both yield and your bottom line. Joining us today is Dr. Mandy Vish, University of Missouri extension plant pathologist. Through research supported by Missouri corn, Mandy is helping farmers better understand these diseases and developing management recommendations that are tailored specifically to Missouri growing conditions. Mandy, thank you so much for joining us. And let's start off with tar spot. It's been in Missouri for a while, and I want to talk timing, but before we get to that, let's get the state of the of tar spot in Missouri. What's going on?
[00:00:59] Speaker B: Yeah, so this year, similar to the four previous years, we've seen tar spot and confirmed it in June.
So we are seeing it earlier than maybe we had when tar spot first entered Missouri. But when we see these June incidences, most of the time they're low. And so the action item is to scout and monitor to determine if we need to make a fungicide application later.
And so that's really where we are with most of the incidences we've seen. We do kind of have two corn crops, or corn is all over the place this year. We have some early planted corn that's in the R2 growth stage, and then we have some corn that's been planted within the last couple of weeks.
So really, as we're making these decisions, taking into account the growth stage of the corn and where that tar spot is on the plant, we really want to protect the ear leaf of the corn. That's our goal with our fungicide applications. And we really haven't seen anything yet this year, at least. I have not seen anything that would warrant a fungicide application for tar spot yet.
[00:01:59] Speaker A: I want to go into southern rust as well. Last year was just crazy for Southern rust in the Midwest as a whole. But as I understand, it was really an anomaly. It required a bunch of different conditions all happening at the same time for rust to get so far north. Is that the case? Are we seeing a low concern for Southern rust? Should folks be scouting for it? What are your thoughts?
[00:02:26] Speaker B: Yeah, David, So last year was hopefully an anomaly. It was pretty unique with everything that happened. So far this year, we've been scouting for southern rust. I know we have a lot of retailers out there scouting, and the only southern rust confirmations in the United States have been in southern Texas so far. Now, you have to keep in mind with southern rust is a little different than tar spot, because the fungus that causes southern rust cannot survive Missouri winters. So it's always going to have to come up from the South. So we have some maps in place and some resources where farmers can check in real time where southern rust has been confirmed. And so far, again, we have no confirmations in Missouri. That's another reason that we want to approach our fungicide applications conservatively.
So last year, we did have some panic when we salt our spot in June, and we had some farmers go out early to spray. And then, unfortunately, when southern rust came in, the residual from that fungicide had worn off. And so we're trying to hedge our bets here. It's not an easy decision, and I understand that. But I do think we have some resources that can help guide farmers.
[00:03:28] Speaker A: Humans are creatures of habit. We like to have regularly scheduled events, but unfortunately, when it comes to crops, that's not always the best practice. When is the best time for spring as opposed to just keeping an eye
[00:03:44] Speaker B: on the calendar, Right? It's a good question, David. So we usually see tar spot early in the season. We'll see it in the lower canopy, and you're just kind of monitoring it. The action item is monitor, monitor wait. Waiting is hard. I know, but with. With tar spot, it really is monitoring until we get to seeing it. Maybe one leaf below the ear leaf. Maybe, you know, if you see it two leaves below the ear leaf and it's noticeably spreading on the leaves, then you can start to prepare. You really want to hold off to spray between tasseling and through that R3 growth stage one, that's the best protection for the ear leaf. And you're going to optimize your chances of the residual fungicide being present for that whole sensitive window when it comes to southern rust. A little more aggressive. But that means that if I'm monitoring the maps that are available, and I know that southern rust is in my area, and I know that my corn hybrid is susceptible to southern rust, then if the weather is hot and humid, then I'm okay making that application, knowing that southern rust can be very aggressive when it's hot and humid. And my if my corn is in that VT to R3 window. So they're two different diseases. Not all diseases are the same Unfortunately. And so understanding how Tar Spot and Southern Rust are different can help when trying to make that decision.
[00:05:05] Speaker A: You said monitor, monitor, monitor. Yeah, we're going to go back to scouting. We've spoken of it a couple times now, but let's really dive into what it means to scout in 2026. Are we talking about looking every week, every couple of days?
[00:05:20] Speaker B: It's a good question, too, David. Unfortunately, Tar Spot and Southern Rest are not like water hemp, not like our weeds, where you can just assume they're going to be there.
So when I say scout right now, I'm basing it on the weather conditions that we currently have and what I'm seeing around me on those maps and where confirmations have been. Okay. So I know for Tar Spot right now, for instance, in Missouri, our confirmations have mostly been in west central Missouri along the Missouri River. And so for those people, I'm going out. It's really hot right now, probably just once a week to look and see if it's progressing because Tar Spot does not like these hot temperatures that we're having. So it's there but not spreading. For Southern Rest, I'm really just observing the plants when I go out to scout, but not necessarily going to scout for Southern Rust at this point. And that's simply because we have not seen seen confirmations in any states neighboring us. For something like Southern Rust, you might see it on the edges of the field first. So if you're worried about that, then that might be a little easier to scout for because you would expect it to move into your field so it would move from the edges.
Whereas for something like Tar Spot, you're probably going to have to do some walking. And. And I do. We do scout our own corn trials. So I know what it's like to go in. It's not a lot of fun.
[00:06:37] Speaker A: Well, it's both a blessing and a curse. But thankfully, when you do go scout for Russ, you don't have to look too hard because you come out looking like you got a spray tan. So folks at least have that going for them.
Missouri Corn is investing specifically for Missouri Answers when it comes to some of the fungicide requirements and decisions that folks make.
Tell us about some of the Chekhov funded research at the University of Missouri. What's the timing like? What's this one pass versus two pass program? I want to know more about it.
[00:07:13] Speaker B: Yeah. Thanks, David. So we've been blessed with support from Missouri corn growers and complementing some north Central Sare funding, we've been able to do some on farm work. So on Missouri farmer fields where we've evaluated a one pass fungicide application compared to a two pass fungicide application. And so for the farmers who participated, you know, they selected the products that they wanted and they were already making a fungicide application at tasseling that VTR1 growth stage. And so then 21 days later, in most situations, we came back in with a drone and sprayed strips within that field to evaluate. And so what we found was it looks so much better the second pass. If you have disease in your field, the leaves do tend to look better. Okay, disease severity is reduced. But when you go to look at yield and you go to look at return on investment, then we have not seen it yet in either our low disease severity situations or our high disease severity situations. Now what's lacking on those on farm trials, David, is it gets really complex to start adding additional treatments and timings to an on farm trial. Otherwise we take up the farmer's whole field and they'd have to slow down a lot. So it's not always practical. So we're complementing this on farm work with some trials at our research stations where we can add more treatments.
And what we've seen so far is consistent with what we have found in multi state studies. And that is that really in low disease severity conditions, we do not see a consistent return on investment from the fungicide application when compared to non treated corn.
But when we do have disease present, that single pass, usually a little bit later than VT actually. So maybe near to the R2 stage has been our best performance in our small plot research. And so that has done as well as a two pass in those small plot trials.
[00:09:06] Speaker A: Now we know those field days can be pretty busy, so let's get a head start on that. What are some dates farmers can visit to see your research? Are there any other resources you'd like to share from our conversation today?
[00:09:17] Speaker B: We do have the field days starting up August 6th, there'll be one in Northeast Missouri. August 26th, there'll be one in northwest Missouri, a field day. And then there's usually a field day down in southeast Missouri and southwest Missouri. And those are at the end of August to early September. And so there are opportunities to physically meet and then there are online tools that are available. So a lot of our Missouri data that we've generated goes into the Crop Protection Network website. And that website is a bunch of extension specialists who have put together fungicide efficacy charts, return on investment calculators, disease risk prediction models.
There are a lot of tools available on the Crop Protection Network and Missouri Data has contributed to those.
[00:10:00] Speaker A: Mandy Bish is with the University of Missouri Extension joining us today. Thank you so much, Mandy, for your time and thanks for sharing all the information you have.
[00:10:09] Speaker B: Hey, thanks for your time and we appreciate it and we're always glad to take questions, so thanks, David.
[00:10:14] Speaker A: Well, diseases like tar spot and southern rust continue to challenge corn growers, but Missouri specific research is helping answer the questions that matter the most. Through investments in research and partnerships with the University of Missouri Extension, Missouri Corn is working to ensure farmers have the tools and information they need to make sound management decisions and protect profitability.
Thanks for listening. As always, this Corn Talk podcast is made possible by the Missouri Corn Merchandising Council and the Missouri Corn Growers Association. To learn more about Missouri corn's efforts to build demand at home and abroad, visit mocorn.org I'm David Geiger. Until next week, everybody.
