Disease: The Biotic Stress Threatening Your Crop With Brian Foss

Disease: The Biotic Stress Threatening Your Crop With Brian Foss

How do you minimize diseases threatening your crop? The first step is to learn as much as you can about these potential diseases. Todd Steinacher’s guest today is Brian Foss, Plant Pathologist at AgReliant Genetics. Brian shares with Todd about the PCR pathology experiments he conducts on hybrids and inbreds. Join in the conversation to get the latest updates on pest management, disease identification, prevention tips, and more. Learn more to make better choices. Tune in! 

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Disease: The Biotic Stress Threatening Your Crop With Brian Foss

I would like to introduce our guest, Brian Foss, who is a Plant Pathologist with AgReliant Genetics. Welcome to the show, Brian.

Thanks for having me, Todd.

Brian, if you would share a little bit about your background and your agronomic journey that has led you to do what you do now.

I grew up in North Eastern Illinois, Grundy County. I’d call it a modest, average Midwestern farm. At our max, we probably farm under 1,000 acres of corn, soybeans and a little bit of wheat. That wheat was thrown in because we were also to finish ag operations so we needed to have somewhere to run the honey wagon come July usually. On that home farm is where I started. Out of high school, I thought I wanted to go into Ag Engineering but my dad convinced me to stay home for two more years and attend Joliet Junior College to get some of my basics out of the way. Even before I’d taken an Engineering class, I knew I wanted to be closer to production agriculture still.

I switched my focus to agronomy. I left the juco and transferred over to Purdue University. I finished my Bachelor’s there in Soil Crop Science in the Agronomy Department and realized that I still wanted more education. I started looking for Master’s programs. I became interested in integrated pest management but that was way too broad for a Master’s degree so I had to focus on one of the areas. I was looking hard at weed science but got a pathology opportunity. It opened itself up to me and I could stay at Purdue, which seemed appealing since I’d only been there two years. I entered this Soybean Pathology Master’s program and it snowballed from there. My major professor asked me if I would stay in his lab and work full-time with him in his soybean project after I finished so I did. I was in Soybean Pathology for a few years before I finally left the university world and came to the industry with AgReliant in 2011.

A great past there, Brian. I’m glad you found your passion in agronomy specifically pathology. I don’t think I’ve ever talked to someone that was on the pathology side. You could talk to basic agronomists or weed scientist folks. From a pathology standpoint, to me, that piece has always been intriguing because there are so many pests out there that are going to attack our corn, beans and wheat. They’re always attacking whether it’s the roots, leaves, early-season roots or late-season stocks everywhere.

We got to manage those pieces. In environments, we try to manage things but with weather, temperature, more heavy corn-on-corn or maybe lack of tillage, it seems like we try to move the needle forward but Mother Nature has a critter out there. Once we put a seed in the ground, she’s going to send something to go eat it. Why? I have no idea. From my standpoint, I like cheeseburgers, PONY shoes and things that are already prepared for me but if you take a pathogen, it wants to go into start gnawing on a root right away. To me, the pathology side of things has always been somewhat intriguing.

YMP 18 | Threatening Your Crop
Threatening Your Crop: The main focus of the pathology department is the characterization of hybrids and inbreds that are at higher testing levels.


I like that point but I carry the flip day-to-day. I’m hyper-focused on what I do with this pathology research program but I also am a CCA. I need to keep that well-roundedness in my tool bag too to think about all those different aspects of what’s going on. I might be focused on a certain foliar disease at the moment but there are a lot of other things going on that could lead to the susceptibility and what’s going on in that field.

Brian, as a fellow CCA and being in the field, I can appreciate how your philosophy is on that. A lot of times, I get to walk plots and we might say, “This is going to be a great hybrid but based on the disease to it, stock quality or root strength, it’s not sellable.” For you being in your role coming from a family farm, having that agronomy background and being a CCA, you can science it on the front side as far as what pathogens and score ratings are there. You are also on the backside on why this is important so it’s not just work for you. You understand the full cycle of how it’s going to benefit the agronomy team, the PCR team and how it’s going to influence a farmer’s profitability. The fact that you brought that up, I got a lot of respect for that.

It’s an important part of what I do day-to-day.

Brian, as we take a deeper dive from your standpoint, I know you do a lot of the evaluations of products for AgReliant. Fill us in on that. What does that look like? Are these replicated plots or fields across the country? Do you have regional sites where you make your valuations?

The main focus of the pathology department is the characterization of hybrids and inbreds that are at higher testing levels so stuff that is about to become available to the customer. We focus on a core set of diseases. We can’t cover everything but what we do is more than enough to keep me busy. These diseases that we’re focusing on are corn leaf blight, gray leaf spot, Goss’s wilt, southern rust, anthracnose and a little bit of fusarium stalk rot also. How do I do that? It’s probably more of what you’re calling a satellite testing location. I have a couple of locations that we tried to place in appropriate areas for these diseases.

For something like Goss’s wilt, I have my later maturity location at Kearney, Nebraska. I test all my maturities. It’s a hard thing to do but if you’re going to pick one spot to test across all maturity zones, it’s in Northern Illinois. I also test early maturities in Sioux Falls, South Dakota. We try to line these things up to an appropriate spot. We don’t have the bandwidth to be trying to do it all over the entire Corn Belt. Something like northern corn leaf blight, I test it in Northern Illinois, in Central Indiana and things like that.

YMP 18 | Threatening Your Crop
Threatening Your Crop: The end game of any living organism is to reproduce and keep the species going.


For gray leaf spot, we’ve got a system developed where we can try and encourage the disease a little bit better. It’s like a Rain Bird sprinkler system that tries to help encourage disease development. A lot of you out there might think that disease doesn’t need any help but when you’re trying to see the full bandwidth of reactions in a small area, we try to do everything we can to encourage that to happen. That’s how we handle testing locations. If the opportunity arises and Mother Nature has provided some disease in a given location, I’ll start traveling to yield trial locations also and look at the hybrids in those environments, score them and allow that to figure into the decision-making process.

You referenced you get to work with all the products that are pre-commercial. Do you have your own plot structure set up? Do you interact with the PCR trials that we have everywhere? Some of those are going to be slightly pre-commercial. Are you making those evaluations? The agronomy team goes through, makes their selections and rates certain things. I’m assuming some of that information gets funneled back up to you and collectively looking at all this data is where you make your rating and recommendation at.

Since I’ve started, I’ve been close to what is now the PCR team. I take the exact trials that they’ve thrown out across the Corn Belt and I duplicate them, other than I will add some pathology checks in so I can tell that inoculation worked the way that I wanted it to. Except for all my plots, I don’t take to yield. All I’m looking for is those disease scores and they’re all small plot research. Our yield trials are 20-foot plots by 4 rows across, single rows and only 7 feet long. All I need to see is that disease reaction in that small space so I’m able to fit a lot of plots in a small area. From this small plot research that we’re doing, I’m able to forward that information to the PCR team and product development. That’s how we’re working in sync. I’ve planted their exact plots, given them the best disease score that I can on that material and then forward it to them in the fall before the advancement meetings. These disease scores feed into the advancement process that way.

I like how everything’s integrated. We got multiple eyes in different modus out there to make the selections and feed information into the machine. I got a question from when you rate things, say specifically gray leaf spot. We know that it’s going to leaving the soil and it’s going to be jumping up the plant. When you give a score for gray leaf, if you see gray leaf out there that might be different than, “We have gray leaf but yet, it’s aggressively growing at or above the ear leaf.” When you give a rating for it, is it based off, “I see gray leaf spot so I score it,” or, “This plant suppressed it from the knees down or it aggressively grew because the hybrid is susceptible.” How does that work from your scoring standpoint?

It’s like what I talked about with our special sprinkler system for gray leaf spot. We’re trying to develop the disease to the max that they could possibly develop on a given entry. What I’m hoping to see is fully what that plant is either capable of fighting off, how resistant it is or how susceptible it is. In my trial area, I want to see the whole range from the dead to almost looks completely healthy. Thinking of it from those terms, what I do when I walk into the test is I’m looking at the percent of disease in the entire canopy of that plot. Not just your up or down but what percentage of damage has been caused to the leaf’s tissue from that specific disease.

Stay well-rounded to get a handle on all the different aspects of what’s going on.

Brian, as it relates to pathogen in general, why does it want to attack a plant?

That’s what nature has developed them to do. I don’t like pathogens and weeds a whole lot but weed has evolved in a specific way. I only talk about them because they’re a little bit more obvious. We see the weeds and we understand what they’re doing a little bit better because we see them. It’s something physical and tangible that we know the whole process. A weed has evolved specifically to take advantage of certain situations. The same is true with our pathogens. They’ve evolved to take advantage of different scenarios and their whole endgame is the same as any plant or any living organism, honestly. It’s to reproduce and keep the species going. That’s why it attacks. It’s found this chink in this example, corn, in a way to keep itself going.

The pathogens don’t care if it’s 300-bushel corn, a cash crop or whatever it is. It’s almost blind. It senses a food source. To me, its job is to survive, reproduce and keep its species going. If there isn’t a root there or leaf there then their species can’t keep flourishing. From our standpoint as agronomists and farmers, we got to understand what these pathogens are. Not just know that they are pathogens but got to work around them and still make good agronomic decisions that can minimize a lot of these pieces.

To me, think about whether it be a bug eaten on a leaf or a pathogen feeding up through the leaf itself. It’s breaking down the leaves, which are the solar panels. If we destroy the solar panels enough, we’re going to inhibit quality photosynthesis. We don’t have any energy. Plants are not going to be able to reproduce near as efficiently. It’s going to cause respiration problems. It’s this trickling effect because one organism was hungry. It’s almost comical to think of it that way but that’s what it is and our job is to minimize it.

Whether it be the minimization out there in the grower’s field or try and reduce the impact that thing has even before it hits the bag.

That goes back to what you bring to the table. Often, people don’t look at product guides or evaluations. Your team pre-evaluates products to know how it’s going to handle. If we know there’s a hybrid that’s good from a yield standpoint but we know it’s a little bit weak in gray leaf spot then 9 times out of 10, we probably should have put it into a heavy corn-on-corn situation. There’s a lot of residue out there or put it into a no-till situation where there’s a lot of residue or put it into a field where we know we can’t go spray it if there’s a problem.

YMP 18 | Threatening Your Crop
Threatening Your Crop: Bury the residue, help it decompose, and remove it from the situation.


To me, we know these pieces. We just got to be better stewards of the knowledge and make these recommendations. On the spraying piece, we do have fungicides out there that can help prevent and minimize some of the pressures but it goes back to a plane and helicopter can’t get in every field. Whether it’s a tree line or near a subdivision, the windmill is going up across the Midwest. To me, understanding what hybrids can go where from a logistical standpoint makes a lot of sense. It may be different than it was several years ago or so.

Honestly, there are definitely years where the economics of it are hard to grapple with too. There’s probably going to be a decent amount of fungicide apply. We’re in a fortunate situation where commodity prices are doing well. When that’s not the case, you have to weigh those different options and figure out what’s right. Fungicides may not even be an option economically in certain seasons.

Brian, as we think about diseases, it seems like there are certain types of diseases that attack a corn plant, wheat, beans or maybe the grass in your yard. What makes one disease favor a corn plant over something else?

There are a few pathogens that can cross over but there aren’t too many of them. One that comes to mind would be the pathogen that causes charcoal rot. We know of charcoal rot in both corn and soybeans. It’s got a broad host range. That’s not always the case with these pathogens. Through evolution, they’ve figured out that niche as to what they survive best on, evolve and run with it. It’s the simplest explanation for how these things have adapted and evolved to be specific to a certain crop.

I would assume based on regional geography, the number of crops may be in a situation where it’s more of a mono-cropping system where it’s heavy corn-on-corn, there are more hosts and residue for it to live on. Versus if you’re in a stronger rotation or maybe corn is only in that situation every 3 to 4 years, those populations can dwindle a little bit. How does rotation play into this?

YMP 18 | Threatening Your Crop
Threatening Your Crop: The more you can know about the diseases that are common in your area, the more you can make informed choices.


It does depend on the disease we’re talking about. The foliar diseases and even some of the stock rots, too, rotation away from corn will definitely help reduce the initial spore lobe. The one case that we know right offhand that isn’t would be southern rust because those spores are floating up from tropical areas every single year. They’re not surviving in residue on the ground every winter. With diseases like gray leaf spot, northern corn leaf blight and Goss’s wilt, that will help reduce the initial inoculum load that’s available the next time that corn is planted in that field.

That’s where we’re field history comes into play. A lot of times when guys get done harvesting for the year, they’re ready to call it quits and they want to forget about the last year. To me, it’s so important to log which fields had major pressures. In spring, if we did have a major pressure, gray leaf spot anthracnose, we make sure we’re not putting that susceptible hybrid back into it. The least amount of pressure is even before it hits the bag from a corn standpoint. Once we throw it in the soil, all we’re relying on is its genetic potential and genetic lineage on how well it’s going to handle some of the diseases out there.

Field history to me is so important to make those decisions moving forward. Especially if we get in more situations where we got a lot of corn residue or maybe we’re not seeing as much deep tillage where the residue is getting incorporated. We’re seeing more either no-till strip-till or we’ve got more vertical tillage. It is sizing the stocks and the leaf material more but it’s still there. To me, we’re not seeing too much breakdown. We have traits out here so we’ve got stronger stocks and all these other pieces so more material for these diseases to live on.

That’d be another way that you can reduce that initial inoculum load. Rotation without any type of tillage is still going to leave residue around. I’m not saying go out and plow to get rid of disease leaf tissue either. Any tillage that could be done on some of these problem areas is going to bury that residue, help it decompose and remove it from the situation.

The phrase, systems approach, gets used a lot in production agriculture. To me, this is part of that system. It’s understanding what’s going into and what’s coming out of it. It’s not just, “Let’s go plant corn.” Maybe that’s what used to be done but there are so many pieces that play into this on making decisions. If I make the decision to not rotate, I’m going to go corn-on-corn, which allowed this problem. I then decide to do a vertical till and then no-till until 2022. I still have all these other problems.

Learn about the diseases you’re concerned about in your area. 

One problem could lead to four problems in a couple of years. That’s why it’s so important to know products and what’s going on. I’m working with a solid CCA or the agronomy team within AgReliant and AgriGold to make these more refined decisions. I don’t want ever to talk like it was a bad decision. If we can tweak these little things along the road, we’re going to have less stress on the plant. It’s going to be able to go through physiological maturity respirations that can be as big of an issue. Maybe we got a more aggressive plant to where it can handle that from a yield standpoint.

If we’re looking for average yields, maybe some diseases can come in there and maybe we’re not totally worried about it. These guys are shooting for these higher yields. We can’t have any stress on that plant, specifically corn plant. We never want to have a bad day. If we got something chewing and eating on it, all that energy could be going to a corn seed. To me, it’s vitally important to understand this whole realm.

I moved away from the family farm a long time ago but making those decisions as far as hybrid placement the fall before is not the easiest task. Any extra information that you can pull out of your tool bag ahead of time including things like susceptibility to certain diseases is useful when you are trying to project that far ahead.

To me, the other thing to know is there’s a lot of data in the ag industry on variety trials or hybrid trials. If we look at a plot that’s one-dimensional data like, “This hybrid did well on this plot.” To me, if you don’t know any of the other variables, it may or may not work on your farm. If you don’t know what the tillage was, how long it’s been corn-on-corn and all these pieces that play from a disease standpoint can compromise yield. To me, it’s important to go walk plots. I know a lot of growers do not like to walk plots but there is value especially at certain times to know which hybrids have good disease tolerance or have a major problem with anthracnose coming in late. That might not be a hybrid that you want to put on your last harvested field to make some of these logistical pieces.

There’s probably more focus now than ever has been on profiling corn hybrids. If you’re an agronomist and your cast spends most of the summer in fields, we can rattle off hybrids and the do’s and don’ts darn fast. What can be tricky is as hybrids advance so fast, you have to be on your A-game. A hybrid might get fast-tracked and we get to see it in a small setting. You’re getting ready to deploy it on a lot of acres. You got to have a lot of eyes on those products to make good decisions.

YMP 18 | Threatening Your Crop


Research is definitely advancing in that way. We’re trying to catch up to baseball. There’s a scenario where they know what hitter can hit a curveball off a left-handed pitcher on Tuesdays when it’s cloudy because of all the data they’ve compiled. Research is trying to do the same things with advancing hybrids too.

Before I came to AgriGold, I was in retail for quite a few years. I can remember when fungicides became popular in corn. In the first couple of years, my guys are seeing responses. They’re wishy-washy whether they should be doing it. I can always remember this one customer that says, “Todd, every time I spray fungicide, somebody is making money. How often am I making money?” I sat back and said, “I don’t know the answer to that but that’s an honest statement.” They’re sitting back. We’re going to fly on this juice that we can’t see. We assume it’s in the tank, we’re getting charged for it and it may or may not work.

To me, there’s a lot of, “Here’s the product for a problem but a lot of folks didn’t know they had a problem.” What I learned was, specifically from gray leaf spot, I call it my sharpy trick, I’ll go out with growers that want to learn the science to what’s going on and we’ll go and find a random hybrid. You’ll find the uppermost leaf that has a gray leaf lesion when gray leaf is starting to come in. It’s always going to be parallel to the veins. I’ll take the Sharpie on either end and put hashtags on it. I’ll mark that leaf, mark that plant and come back in about a week.

Based on how much that lesion grew past that Sharpie, the grower can see that there was a problem here. It’s growing. You can start seeing all the other lesions that are starting to show up on the leaf. At that moment, they realize, “We have something attacking my plant. What can we do to fix it?” To me so often, maybe we skip the science and go right to the solution. For the growers that I’ve worked with, we go through the science of how it’s growing. There is something out there. They can fundamentally understand that and make a decision based on protecting the crop not necessarily somebody’s trying to sell to me. I see planes flying around. Should I be doing something? It’s more of a reactive standpoint but to me, education is so vitally important when it comes to disease management on corn.

I agree with that especially if you’re talking about the case of fungicide use. I’m going to view this from the perspective of a pathologist and my thoughts there are, unfortunately, exactly what you’d probably expect. The fungicide is going to pay off when the disease is present. What’s the way to know if the disease is present? It’s hitting, walking those fields and knowing what’s developing and when it’s developing. Part of that too is having a little bit of knowledge about those diseases that you’re concerned about in your area.

YMP 18 | Threatening Your Crop


What are the weather conditions that favor gray leaf spots? Optimal temperatures are 75 to 85 degrees plus, in conjunction with that, it needs to have some seriously long moisture periods for those spores to develop an effect. If those conditions have happened lately and you particularly know your hybrid might have some susceptibility, you’ll probably want to start paying attention with your own eyeballs to those acres in scouting and watching.

There are some pretty decent economic threshold recommendations out there. An old one for gray says something along the lines of if you have a disease at the third leaf below the ear leaf at or before tassel then you might want to start watching those fields and consider an application. There are other factors to consider too like the economics involved, how that’ll play out and what you think a reasonable return might be. I’m always going to say that the fungicides are going to be the most effective when there’s disease present.

A couple of years ago, I did a study with the grower and we wanted to see how much yield was still vulnerable at about 3/4 milk line. We pulled our first sample when it was at 3/4 milk line to signify that the plant shut down from disease, lack of nutrients, whatever it might be. Put it into a potato sack, put it in a shop and come back when you harvest it. Once you get about 3/4 milk, those folks think, “The crop’s done. We’re sitting and wait until harvest.”

When I got the gram scale out, weighed them and did it from a percentage standpoint, I didn’t know what I would find but there’s 24% or 25% yield left to be converted over. In my mind, we want to try to hit all these things early planting and all these other pieces. If we’re not protecting 3/4 knuckle on the black layer, there’s a lot of yield loss there. We can spend a lot of time managing nitrogen because a lot of times it’s still fertility that drives it. If we have diseases, we have gray leaf spots, southern rust and all these other pieces compromising photosynthesis and respiration rates. There’s only so much energy to go around and it’s going to start sucking it out. To me, that is what we have to protect if we’re concerned about it.

These foliar diseases in particular and to some degree stalk rots too. To what degree is not as well known. It affects how much test weight is being packed into those kernels late in the season.

It’s definitely a big player out there for a test. I’m glad you called that one out. Brian, I do want to take a little bit of a curve in our conversation. We referenced several diseases that you watch. Several diseases there’s a problem across the countryside. I specifically want to call a few of them to have a general conversation. From an anthracnose standpoint, we tend to see more late-season, cause stalk rot issues but there’s also anthracnose leaf blight. A lot of guys might spray V4 or V5. I was always under the impression that they’re linked together to what you have. Maybe the leaf blight or the anthracnose stalk rot because you have that. Is that a precursor that you will have a problem? What needs to take place to have that stalk rot problem?

Start paying attention with your own eyeballs. 

If you have the leaf blight then you may have the stalk rot. That’s about the way I would put it too but I stress that may. Surprisingly, there isn’t a strong correlation between anthracnose leaf blight susceptibility and what you see on a hybrid when relating it to anthracnose stalk rot that might develop later in the season. The two aren’t correlated. The resistance to one doesn’t necessarily mean resistance to the other and vice versa for susceptibility.

What it does mean is that pathogen is present in that environment so you do know that the same pathogen is there and there’s potential basically. It’s because you saw the leaf blight doesn’t mean you will have an anthracnose stalk problem later. You do know that the pathogen didn’t have build out. For stalk rot development itself, it seems to prefer warm and more moist conditions. It can, in fact, infect at any point in the growing season but that means it can infect the root system and the stalks at any point in the growing season. It doesn’t necessarily express itself until much later on.

You have great information there. As we think about southern rust we know it’s blown in from the deep south. It’s not going to overwinter in most parts of our geographies but when it comes in it is aggressive. What makes that disease so aggressive compared to maybe some other ones? Is the reproductive cycle that much faster and it can shoot off offsprings that much more rapidly?

Southern rust does have a pretty quick disease cycle so it can keep those secondary and tertiary infections, keep going quicker. The ability of that thing to travel too and how far it can travel right in these weather systems up from the south is also a factor. Other diseases and the spores are carried in the wind too but I agree southern rust definitely does seem to take advantage of some of those scenarios like when you see a hurricane or a tropical storm blow up. It’s often good practice to be watching your feet following that if you’ve again had the appropriate conditions. Southern rust, like gray, warm and wet is going to be the right conditions. Southern rust doesn’t need as long of a latent due period either as something gray does. It’s an overnight due. Six hours plus of moisture on the leaf and infection can occur. Its requirements aren’t as stringent at something like a gray leaf spot.

I’ve experienced quite a bit of it in the last couple of years and it does flourish and it can spread pretty fast. If we see certain weather patterns moving into our environment, we probably need to go scout. I call that out because the last couple of years I’ve seen some hybrids that are I’ll call them rock stars for plant health. Maybe some folks put them on corn-on-corn or maybe don’t plan to spray fungicide on so they see these weather events come in and we’re brown silk so they’re not concerned with it. There are some that can be sensitive to a southern rust flush and not only have problems with southern rust but that southern rust and cause a crown root rot problem or all these other trickling things. To me, even if you think you’re safe, it’s still important to be out scouting your fields.

YMP 18 | Threatening Your Crop


Honestly this particular field I’m thinking of the neighbor sprayed it for fungicides but from a soybean standpoint and every time the plane flew over, it still dribbled some out across the field. You could tell right to the line where that plane looped in over the cornfield. It’s an amazing result right there. Even though we know we’re protected, we had a good plant. We’re so close to 3/4 milk but we still got to be out there watching things in case we need to go protect something.

There are some other tools out there to help us with some of this scouting or advanced warning. One thing I track is called the Corn ipmPIPE. It basically records confirmations of plant samples sent to diagnostic labs at the state universities but it specifically tracks southern rust. When a company has a positive identification, it highlights that county on the map. You can basically watch this. The counties start highlighting down south and work up north. That way you can see how it’s spreading and how fast it’s spreading. They also do the same thing for tar spots.

It’s a good insight. I’ve watched some of those pieces and it is a good gauge. When I can start watching them get close to me, that’s when I start getting concerned. Where I’m at when my counterparts or folks that I know in Southern Illinois started having problems with it. Most likely between there and me we’re going to start having problems. We’ve got more technology now than we ever had to monitor these things or to start calling people in the southern states that have issues and track it up. To me, being aware of what’s going on is so important.

Fortunately, for something like southern rust, it can’t overwinter so it does have to start anew every year. That doesn’t mean we’re safe in any given year but it does have to have the right conditions every year to come back in. It’s not automatic. It’s because you had it last year, you’re not starting with it there present in your field. That’s the one good side to something like southern rust,

Everything has a silver lining. That’s the silver lining to southern rust. It doesn’t live here. Brian, tar spots have been coming into some areas in the last couple of years. Do you work with tar spots at all?

For tar spots, I try to take advantage of what’s showing up in trail plots. Going back to southern rust, southern rust and tar spot are the two diseases that we want to watch that I cannot inoculate for. You can’t grow those pathogens artificially in the lab. We have to take advantage of what Mother Nature gives us. Maybe we can try to do some things or be strategic about where we’re going to look and how we’re going to look. Knowing the weather conditions in certain areas where it has been appropriate for the development of tar spots as well as what I know about that location historically. Is this a site where I saw it a couple of years ago? Was it a corn-on-corn where I saw it in 2021? It’s things like that. If we got into it, you could try to irrigate in the proper temperature range and try and coax it but we haven’t quite hit those stages yet. There are some things you could do even with Mother Nature being behind the wheel.

We’re watching that one pretty hard here in Illinois. It started to creep further down to some of the counties that I cover. It’s probably the furthest south I’ve seen it and probably further south than what they’ve originally projected it could go. It’s definitely a disease that we’re watching here in Illinois. Another one that has crept up the last couple of years is the physoderma brown spot. Are you familiar with that disease at all? Do you have any field evaluations for it?

YMP 18 | Threatening Your Crop


I’ve taken some opportunistic notes on it. I am familiar with it. It’s funny that you mentioned physoderma brown spots right after tar spots because I’m thinking about this. Something like tar spot is building and growing concern. It has gained some steam but the two of these diseases together, 2019 was probably when they hit full steam and got some news attention. It had people talking at the coffee shops. What do we remember about 2019? Not that anybody wants to dredge that again but a whole lot of the corn belt planted a month late, maybe even more, 5, 6 weeks late. What’s that do to our growing season? A disease like physoderma brown spot, the initial infection, we think takes place pretty early in the corn plant’s life. When it’s in younger B stages. B4, B6 or something like that thrives when temperatures are warmer and when the world can get filled with water.

In 2019, what did we do to our growing season? We pushed everything back a month on the calendar. All of a sudden, these corn plants, that would be V10 and V12 are young. They’re V4 when we hit these warmer temperature patterns of June and some of these heavy rainfall patterns that we can get in that timeframe too. All of a sudden, our crop is exposed to conditions that we don’t normally see and it gives an opportunity for diseases like physoderma to jump out. 2019 helped build the talk about physoderma but I do attribute a lot of that simply to that late planting season and exposing our crop to conditions that it generally doesn’t see at certain growth. The same can be said about tar spot in that season too.

Tar spot tends to come on the late season and when it starts to cool down but wet. By shifting everything in the calendar, we still got a lot of green material out there later in the year than we normally would come early October. There were still a lot of green leaves out there and the temperature started cooling down, you get enough moisture and tar spots spread. It’s interesting in that one season how these two diseases gained some notoriety. It was a big problem but by altering that one thing, the planting date, changed our perspective on those two diseases.

I would say in the last couple of years, I’ve been sitting on more training with physoderma trying to put it in profile guides and evaluating things. What I’ve learned is specifically in physoderma when we go do our valuations of hybrid plots, maybe I can see it more in a plot setting. Once I get into an actual field setting, I don’t tend to see it near as heavy. If it gets around the node and it would snap. In some cases if it’s aggressive, it might be a higher percentage in a plot but once you see it in a field setting, it’s not near that. It might just be pockets. Is there anything that maybe things hover more in a plot setting than an actual field setting or if we’re looking at a more of a microenvironment? What are your thoughts there?

I don’t know specifically how to answer that one. It could be a lot of different things. It could be that it happened to be in that right spot and that small plot. It could be the material that you’re looking at. When you’re walking, you’re looking at advanced material. When I’m in these small plot environments, I’m looking at stuff that is still advancing up through the chain so you can find some of those chinks in the armor a little more easily and you almost expect to see a lot more of that stuff because I’m looking at material that’s not as far along. I don’t know what the right answer is. Hopefully, you guys are weeding those things out before it makes it into the large field.

We have to take advantage of what mother nature gives us.

We’ve got a lot of eyes in these fields and we make a lot of observations. There’s a lot of us that understand corn but there’s a lot of stuff we don’t understand. It’s almost like you get flooded with knowledge and it’s hard to sift it out. Hopefully, that thought will have found its way out and found an answer for it. So many things go on in a corn-soybean field that we can’t explain and sometimes Mother Nature knows what’s going on and she hasn’t given us the bread crumbs, if you will, to know what’s going on.

We’re getting there more and more time. We do figure out answers to both of these last two diseases. Physoderma brown spots are by no means a new thing. It hasn’t historically shown up a lot but Mother Nature reveals things and there’s always a pest of some sort that’s there and willing to attack our crop. As our climate does squirrely things year to year, we’re going to see some of these different things show up. When that environment changes just enough to be more favorable for one pathogen than another, you can expect these changes to surface.

Brian, as a follow-up to that. Say that, in the last few years, we’ve seen more of an introduction to physoderma brown spot, maybe most people never heard of it. You would think after so long of not having a problem that disease would wither away. Does it go dormant and once the environment is ready, it wakes up from hibernation? Honestly, before we had it, I never even heard of it. It wasn’t in any of our agronomic journals and young scouting guides from land grant universities so it wasn’t even on our radar for so long. I’m assuming this goes dormant and when the environment knocks, it wakes up.

There are two good things about this. The first one being, the brown spot that we see usually isn’t that big of a problem. For the most part, it’s probably not causing yield problems. The bigger issue is when it can get on the node, you have the stalk breakage and it’s hard to harvest in a year off the ground. As for its ability to survive, the pathogen is related to the same group that pythium and phytophthora come from.

If you know much about those organisms, they can make them resting spores that are hardy and can harden off and survive in the soil for some pretty long periods of time, years and years. That helps explain a little bit about why all of a sudden, we’re getting the conditions for it to show up in a way that’s more prevalent. It’s probably been there for a while and not in a way that expressed itself or caused an outbreak big enough for average eyes to come across.

That’s definitely a unique way of putting it and thinking about it. It’s because we don’t see a pest for a while doesn’t mean it can’t come back so it’s good to stay on top of things. Brian, as we look to wind down this episode as I sit back thinking of some recommendations whether it’s a rotating acre or even a corn-on-corn acre. To me, it still comes down to having the right hybrid that you’ve selected specifically for a given field. Field placement is so important. Seed treatments can be of value from an early standpoint of the early seedling diseases, getting the crop established and getting the root system going.

YMP 18 | Threatening Your Crop


As we started thinking about residue management whether it’s still heavy corn-on-corn, we’re going to strip-till a lot more no-till out there. We’ve got stalks that are living longer because we grew a good crop and we’re doing a good job managing it. A lot of these diseases can live on it so we got to think about how that hybrid is going to interact with the residue that is out there and will be out there for a while.

We’ve also got to be concerned about the diseases that fly in that we don’t control. You almost have to have a game plan for everything. To me, it comes down to knowing your fungicides. Why are you spraying it? Everything you do, you have to have a specific reason why we’re going to do it, what we’re going to go after but then being engaged with your crop and trying to make these decisions. Out of those highlights, Brian, is there anything else that you would add for a recommendation for anybody reading?

The more you can know about the diseases that are common in your area, they’re going to help you make those informed choices. Knowing the conditions that are favorable for disease development as far as the temperature and the moisture available in a given timeframe, as well as what’s going on in your neighbor’s field. How susceptible is the hybrid that you planted? Are you trying to pick something that is going into corn-on-corn? Is it going into a river bottom or an area that tends to be for extended periods that would encourage infection and disease development? The more information you can glean and keep about these diseases, the better decisions you’re going to be able to make about the hybrid replacing in a specific area.

Brian, I would like to thank you for being our guest. I enjoyed the knowledge that we shared here. I’m sure everybody else did. You gave us some great insight as far as how products are profiled from a disease standpoint and the value that goes behind that on how we’re going to place things and understanding do diseases live here. Are they blown in? I like your passion for education and learning about these diseases and field history to make good decisions and it comes down to good agronomy. Good agronomy is fundamental to everything for learning so I do appreciate that. Brian, if you have any parting comments or words you’d like to share with the guest, you’re free to do that.

Don’t be afraid to keep those boots moving and walk your fields especially where you suspect you could have an issue. It’s not always the most pleasant activity. It will come July and August in a cornfield but probably one of your best weapons is your own eyes or a reliable scout hitting those fields and understanding what’s happening, what’s showing up and when it’s showing up.

Great advice and information there. Brian, thank you for being on and sharing your information. For everybody reading, thank you so much. We’ll talk to you next time. See you.

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About Brian Foss

Brian Foss is a plant pathologist for AgReliant Genetics.

After nearly two decades of experience in agricultural research, I have confirmed a passion from my childhood on the farm. Contributing to the advancement of production agriculture is a ceaseless desire. It also happens to be necessary to meet the demands of a booming global population. My greatest pleasure would be achieved by the intersection of these two: engaging in food production while being able to directly educate and assist those in great need.

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