Subscribe
Share
Share
Embed
Dr. Greg Tykla, nematologist with Iowa State University and Dr. Samuel Markell, Extension broadleaf plant pathologist at North Dakota State University discuss soybean cyst nematode and the challenges with managing this pathogen.
Hosts Anthony Hanson, Dave Nicholai, and Bill Hutchison at the University of Minnesota alert growers, ag professionals and educators about emerging pest concerns with Minnesota Field Crops, including corn, soybean, small grains and alfalfa. They offer useful, research-based pest management solutions.
Dr. Anthony Hanson, IPM Educator - Field Crops
Dr. Bill Hutchison, Coordinator of the MN IPM Program
Dave Nicolai, Crops Extension Educator & Coordinator of the Extension Institute for Ag Professionals
Welcome to the University of Minnesota Extension's IPM podcast for field crops. I'm your host, doctor Anthony Hanson based out of West Central Minnesota and covering pest related subjects throughout the state. Today, we have another bonus episode for everyone. This is part of our strategic farming series, let's talk crops. And in this week's episode, we had discussion about soybean cyst nematode, where growers and other participants could ask experts on soybean cyst nematode questions that they had during the webinar.
Anthony Hanson:For just a quick programming note, we'll also be continuing the strategic farming series with a new set of webinars called strategic farming field notes for the summer growing season. So this is your opportunity to be able to ask questions to extension specialists and other faculty throughout the state, anything that might come up during the growing season. These will be held 07:30 to 08:00 in the morning on Wednesdays, starting on April 21. To register for these webinars and to get reminders about them, just search for strategic farming field notes or follow the link in this episode's description. With that, I'll let Angie Peltier introduce the panelists we had for this week's episode.
Angie Peltier:Good morning. Thank you all for attending our Strategic Farming Let's Talk Crops program this morning. Happy St. Patrick's Day to you as well. We're happy to have you join us for today's session.
Angie Peltier:It's called SCN, So Tough a Threat, It Warrants a Coalition. These sessions are brought to you by University of Minnesota Extension and generous support from the Minnesota Soybean Research and Promotion Council, the Minnesota Corn Growers Research and Promotion Council. We welcome two panelists today and a third might join us a little bit later. For more than thirty years now Doctor. Greg Tilke has worked in Iowa State University's Department of Plant Pathology and Microbiology.
Angie Peltier:Doctor. Tilke is a professor and nematologist and his work focuses on the biology and management of the soybean cyst nematode, our topic today. Perfect. Doctor. Sam Markel is an extension plant pathologist at North Dakota State University.
Angie Peltier:His research is in applied management of diseases of broadleaf crops grown in North Dakota and there's a lot of them including canola, chickpea, dry bean, lentil, flax, pea, soybean and sunflower and we also welcome Doctor. Markel here this morning. Doctor. Seth Nave is the University of Minnesota Extension soybean agronomist. He's currently tied up with another Zoom webinar but may be able to join us in a little bit.
Angie Peltier:We have a few housekeeping items to go over before we get started. Now, our goal is to have these sessions to be more of a discussion type format and the discussion will therefore focus on questions we received from everyone at registration and questions we received from you this morning. We'll have about ten minutes of information presented by our speakers today on the general topic and then we'll open things up for questions. With that, I will turn it over to our panelists. Gentlemen?
Samuel Markell:Morning Angie. Thanks.
Greg Tykla:Hello. Hi Angie. Thanks for this opportunity. Sam, do you care if I kind of launch us?
Samuel Markell:Go ahead, Greg. It'd be good to hear about SCN from the master.
Greg Tykla:Well, I always kind of think of my target audience. And so Angie, I think, really hit a home run when she asked Sam and I to participate because part of Minnesota soybean production area is very similar to our SCN situation in Iowa. And then there's another part of the state of Minnesota that is very similar in the SCN situation to Sam. So I think we both have maybe tales to tell that will be applicable to the soybean farmers of Minnesota. So the situation in Iowa is that SCN has been around for a long, long time.
Greg Tykla:It was found in Winnebago County, Iowa in 1978. That's in Extreme North Central Iowa, and it's the same year and right across the state border from Fairbow County, Minnesota, where SCN was found the exact same year. So literally, Iowa and Southern Minnesota have been battling this pest pretty much on the same timeframe. And in the eighties and nineties, the the real effort was just to get farmers to know they should test for SCN. And if they found it, they could literally grow virtually any resistant soybean, and the problem was taken care of because the resistance was effective.
Greg Tykla:But over the nineties and the February and the twenty tens, there was a problem brewing underground, and brewing might be an appropriate verb considering it's St. Patrick's Day today. And that was that all the soybean varieties everybody grew had the same source of resistance. It's this weird thing called PI eighty eight thousand seven hundred and eighty eight. And so we managed SCN in Minnesota, Southern Minnesota and Iowa in the eighties and nineties and February by not really thinking about it, just growing a resistant soybean.
Greg Tykla:But as I speak with farmer audiences, I say to them, can you imagine what would happen if you used a single herbicide for twenty five years? Do do you think what would happen to the effectiveness? And, of course, people start to giggle because they know what I'm alluding to, and that is herbicide resistant weeds. It's the exact same force of nature that has happened with SCN. And in Southern Minnesota and throughout Iowa, now the SCN populations have become resistant to PI eighty eight thousand seven and eighty eight, and that's quite a battle now.
Greg Tykla:So we have to broaden our perspective and think about what other things we can do to manage SCN, and we have to be more active. We have to purposely think about managing SCN, which is hard because for thirty years we were on cruise control, and all we did was grow a resistant soybean. So I think I'm gonna stop there and let Sam frame things up from a North Dakota perspective.
Samuel Markell:Good morning everyone, and happy St. Patrick's Day. So when Greg and others, and those growers in Southern Minnesota and Northern Iowa were discovering SCN, North Dakota growers were discovering soybeans. And it was a pretty new crop, and we didn't have a lot of acres. So as you might imagine, we didn't have to worry about SCN.
Samuel Markell:Just as a reminder to everyone, SCN is invasive. It showed up in North America in the 50s and continued this march across the country. So early 2000s we had several million acres of soybeans and still expanding. We found SCN in Richland County. So this is the Far Southeastern corner.
Samuel Markell:So that's right across from Wilkin. And shortly after we found it in Cass County and that's right across from Clay where Moorhead is. And we had a confirmation in three counties in the state up until 2010. And then we started really looking at it more actively. The North Dakota Soybean Council got involved and now it looks like we've got it in 24 counties.
Samuel Markell:Now we have SCN really severe in a couple, but just an occurrence or two and a few others. So it's continuing to spread. And as you all know, as you get more north, your maturity groups change. And initially we didn't have a lot of SCN resistance at all. So there was a lot of susceptible varieties that were being grown and so our populations got pretty high.
Samuel Markell:And then often when you do get the resistance in the variety, there's other things that growers consider iron chlorosis or whatever else it is. And so it became a bit of a challenge a decade ago to select a variety, find a variety in maturity groups, it and start to use it. Nevertheless, we in the last couple of years have also started to see that eighty eight thousand seven eighty eight, this source of resistance that Greg talked about is starting to be overcome by the nematode. And it's still useful, it's just that the nematode is starting to be able to reproduce on it. Its efficacy over time is dropping.
Samuel Markell:And I would say that the situation in Northern Minnesota is very analogous to what I said and the situation in Southern is very analogous to what Greg has said. And I see Dean Malvik on here too, at least his name pop up. Greg and I both work with Dean, he's a pathologist, he can make comments as he wants, but I would assume that he would see and say the same thing.
Greg Tykla:And if I could drop one more Minnesota name also, I've, over the years, found that Bruce Potter is is has some real real life experience boots on the ground with SCN. So I can't see who's connected here, but he would be another local resource to turn to for firsthand real life experience with SCN.
Samuel Markell:So, Brad, where do you see this going with 88,788 resistance? What you think is So, gonna
Greg Tykla:we are rapidly approaching a very tall, very sharp cliff that we're gonna fall off of. It's, I call it a slow moving train heading towards a cliff. It's not gonna get any better. It's a force of nature, kind of literally and figuratively, and more and more nematodes are going to develop the ability to reproduce on 88788, and eventually all resistant varieties are going to be susceptible, not because of the genetics of the variety, but because of the genetics of the nematode. And I think one of the the topics that we were we were told at the registration process was of great interest was we'll see companies develop more varieties with other sources of resistance.
Greg Tykla:Peking is the primary other source of resistance. And boy, I I've never been accused of being overly optimistic. I'm more of a realist. You know, there's nothing more Angie or Sam or Dean Malvik or Greg Tilke can do to convince the seed companies to develop more varieties with peaking resistance. It just if they haven't heard it from us, they're not listening.
Greg Tykla:So I've turned my approach in the last year or two to the farmers. It's like, hey, you guys and gals are the ones that are gonna suffer. You're the customers. You need to start to demand these varieties. It there's nothing, as I said, Angie or Dean or Bruce Potter or or Sam or I can do to convince these seed companies.
Greg Tykla:And obviously, the big distraction is herbicide tolerance. Everything that's new in the soybean world is herbicide tolerance. So I don't know how to prevent I don't know how to slow the train or stop the train from going over the cliff. But I'm my money's on mother nature, and there is no doubt this is gonna continue to get worse. It's part a cool but sad part of my job is I love biology, and this is biology at work.
Greg Tykla:There's nothing humans can do to stop this biology other than throw some different genetics against the nematode.
Samuel Markell:Greg, they should have cast you for Jurassic Park. I think they wasted their money on Jeff Goldblum. It could have gotten you much cheaper.
Greg Tykla:Well, I think my words are being taken seriously about equally as Jeff Goldblum's. I really hope by putting the the emphasis on the farmers, the customers, we need an outcry of customers saying, this has gotta stop. I don't that's my best last hope to to slow this problem down. And I agree. I wanna concur with Sam that we can't give up on 88,788.
Greg Tykla:We there's not enough new genetics in the world for us to stop growing 88,788, but we desperately need new things to space in a crop rotation program with eighty eight thousand seven hundred eighty eight.
Samuel Markell:Yeah, and you've had good success with that. Know, you have growers down there and I've talked to one of your growers, Ron Heck, about how he's been able to manage it sprinkling in different genetics, right?
Greg Tykla:Again, it's a force of nature. It'll work. If the farmers are able to do it, it will work.
Angie Peltier:So would you guys mention the SCN coalition and your roles in it and its goals?
Samuel Markell:Sure, we'd be happy to. So Thank the SCN coalition is something that started in 2015 and really got wings in 2018. And the whole concept here is that SCN is too big for one person, one university, one company to manage alone. I mean, really truly is. And over that three year, four year time period, there were a group, there were people, and Greg and I are co leaders of this along with some others, and we were going to the private sector.
Samuel Markell:We were talking to them, trying to figure out what they could do, what they were willing to do, going to universities, what could they do, and what they needed for success, and really what we did is unified the management messages. There's not a lot of new tools out for SCN. The tools are really not necessarily the issue, but actively managing and incorporating those tools is something that we need to do, at least initially. And then more peaking, we assume, will come and we'll be able to handle this. So right now there's eight agrochemical companies, there's two dozen universities, there's state and regional North Central Soybean Research Program, and nationals, so USB, soybean checkoff organizations that are engaged in this coalition.
Samuel Markell:And the coalition has enough funding to operate, and then the companies have been very generous with their in kind support. They've contributed money directly too, but the in kind support I think is actually more important because media machines that we don't have at the university. I mean, they have big advertising budgets, they're really good at marketing, and they do those things really well. And so they've worked with us to try to get that message out. And so just as an example of the last thing that the SCN coalition did is we put on a program called Let's Talk Toads.
Samuel Markell:And so this was in 2020, and we filmed mostly in the summer, a little bit into the fall in 2020. And I think Greg, if there's 24 videos initially, I think there might be 30 or 31 right now. We filmed in four different states where we were talking to growers, talking to people looking in the field, talking to like Craig's grower about how he managed SEM, or one of mine. And those videos in the first six weeks had over 900,000 views. And part of that was the advertising machine, helping us get that word out.
Samuel Markell:And each of those videos is two to three minutes long, and it talks about specific opponents of managing SCN. So a grower can visit that website, a la carte, just pick them. So the SEN coalition has tried to move the needle on getting producers as much information as they can, so they can make the best decisions for their farm. One size does not fit all, I mean, the growers in Iowa and the growers in North Dakota, in addition to having things like football rivalries, they might not do things the same way. Our soybeans don't look exactly the same, and we could rotate with different crops.
Samuel Markell:Dry edible beans are susceptible to SCN, so we have to be aware of that. So anyway, thesncoalition.com is where all this information is housed.
Angie Peltier:So we did put that in the chat for folks. Go ahead and visit the SCN coalition website like Sam said there's tons of resources there. You mentioned dry edible beans Sam as being another host of SCN. Steve Olson here asks the question, what other crops can be a host to SCN?
Samuel Markell:Yeah, so drivable beans are the primary one we're concerned about. So, and it's not quite equal across the board. Drivable beans have a couple different centers of origins, their genetics are kind of different. So what we tend to see is that the SCN, the nematode really likes kidneys. The reproduction on a kidney bean is essentially the same as a susceptible soybean.
Samuel Markell:So kidneys are probably at the greatest risk. The Pintos and navies and blacks would be probably a moderately susceptible, maybe even a moderately resistant soybean. That would be kind of the level. So they're all sensitive, but there is a difference in market classes and kidneys, growers that grow kidneys and you have more Minnesota kidney growers than North Dakota kidney growers, really need to be aware of this. Greg, do you want to talk about other hosts?
Greg Tykla:Well, I would just add, yeah, to that. I that the national leader on SCN reproduction on non soybean host is a colleague of Sam's named Berlin Nelson. So if, anybody wants to hop on the Internet and look for the research Sam has been describing, just look for Berlyn Nelson beans SCN. I believe he also found that black beans are a really good host for SCN, although I wouldn't stake my wife on it. I'm pretty sure there was two main classes that were really good and others that were kinda moderate or, not so good host.
Greg Tykla:And the only other thing I would add to that is most peas, and when I think of Minnesota, I think of Lassure and Lassure peas in Southern Minnesota. Back in the days of Ward Steenstra in the nineteen eighties and nineties, he worked on SCN and peas aren't the best host. They're kind of a moderately good or moderately not so good host. But they are somewhat of a host. They'll allow some reproduction.
Greg Tykla:The real cautions are the one Sam alluded to, the edible beans in the kidney class and I think maybe the black bean class.
Samuel Markell:I I I think it's actually maybe the Pintos that is a little bit more Oh, okay.
Greg Tykla:I knew there was two.
Samuel Markell:Yep. Pintos are a little bit more sensitive. Yeah.
Greg Tykla:And Berlyn Nelson not only showed reproduction at very high levels, he documented pretty high levels of yield loss as well. So it definitely needs to be managed if you're growing these edible beans.
Angie Peltier:Thank you. So an anonymous attendee asks, essentially says herbicide resistant traits have been stated as a deterrent to incorporating the other SCN background. I think they probably mean Peking. What is so hard about incorporating the other background?
Greg Tykla:I'll take a whack at this. I'm not a plant breeder. And I see in the attendees at least one person I know Dennis, who's a plant breeder. And so please forgive me if I oversimplify things. But my perception is that when seed companies make new varieties, they don't start back with breeding lines.
Greg Tykla:They start with among their best already existing varieties. So what's the situation with most seed companies existing varieties? What do they have for SCN resistance? They have Peking. So for a seed company to develop new herbicide resistant varieties with the Peking resistance, my perception is it's gonna be a lot more effort.
Greg Tykla:Unless they're lucky enough to have a good pea king resistant variety that they can then branch out into new herbicide resistance. So the problem of almost everything having PI eighty eight thousand seven and eighty eight resistance is plaguing the breeding community is my perception, as well as the farming community.
Samuel Markell:Yeah. You would assume too that if 97, 95, 90, whatever it is, of all the varieties have 88,788, that probably the best yielding ones the company wants to breed into just by odds, know, nine out of 10 varieties are more likely to get your best one there. They're going to use those first intentionally, not necessarily because resistance, but intentionally because that's what they have in their yield profile, right? I mean, I would assume that's the case. Even though there's not necessarily a yield drag though for P King, right, Craig?
Greg Tykla:Well, that's an interesting question, Sam. There is a there's a yield drag for PI eighty eight thousand seven and eighty eight now. The yield drag for Peking was because of the plants genetics. If you had no nematodes, Peking almost always is going to yield a little less than varieties with eighty eight seven, eight, eight. But there's a new yield drag in the neighborhood these days, and it's called SCN.
Greg Tykla:So now we see Peking varieties among the best and often better than the eight, eight, seven, eight, eight varieties. It's because of what I mentioned earlier, You can't just ignore the genetics of the nematode. We ignored the genetics of the nematode for thirty years, and we benefited from it. Don't get me wrong. We thrive with PI eight eight seven eight eight.
Greg Tykla:But now, very few fields don't have SCN, so the yield drag of Peking is irrelevant. The yield drag on eight eight seven eight eight because of nematode reproduction is is the thing that's affecting most farmers. So good question. And if I can transition to another question offered up, somebody asked about Dean actually, Dean Malvik asked about transgenic soybean resistance. And so I have a little bit of experience with that.
Greg Tykla:Personally, there is one company BASF that has received approval from the US EPA to proceed to bring a transgenic SCN resistant source to the market. And all I can say is mainly because I can't remember data off the top of my head, we've tested it in the field and it looks promising. And they're testing it in many more geographies. And, I think you'll see it over the next two, three, four years, continue to develop. I think we're literally two, three, four years away from a farmer being able to buy it.
Greg Tykla:But there is, at least that company and I can mention that company because they publicly had to get approval from EPA to, continue to work on bringing transgenic SCN resistance to market.
Angie Peltier:And so that transgenic SCN resistance is that effective against all of the strains or HG types of SCN that are in your fields down in Iowa?
Greg Tykla:That's a good question Angie. We're actually working to study how to answer that question in a little different way. We're working to see if it shifts the HG types when you grow the same transgenic resistance over time. Knowing how that transgenic resistance works, I don't think it'll be a problem. I think it will work on all HG types because it's a BT type of resistance, and that's completely different than the normal soybean resistance genetics.
Greg Tykla:So, it would be a really weird, quirky twist of nature if it actually shifted things or worked better on certain HG types than others. It should be agnostic. It should it should affect all HG types the same, but we're actually doing experiments to to kind of verify that that's the truth.
Angie Peltier:So we've had several questions come in from Dennis, from Clyde, anonymous attendees. They're wondering about seed treatments and I wonder about seed treatments too. Know with SCN you can
Samuel Markell:have
Angie Peltier:multiple generations per growing season and you know our roots keep growing into areas that might not have any of the seed treatment active ingredient in it. What are your thoughts about seed treatments biological or otherwise and SCN management?
Samuel Markell:So, yeah, sure. So when I talk to growers about seed treatments, the very first thing I try to emphasize is that unlike some of the fungicides and herbicides that we work with, seed treatments for nematodes are all over the place in how they work. There's biologicals, biological parasites, there's a fungicide or two, there's neurotoxin I think, there's one that tries to get the natural immunity up on the plant. There's very broad range of how they work or they're supposed to work, so it's a little difficult to say they're good or they're not, so keep that in mind. I don't have a ton of data here in North Dakota on seed treatments.
Samuel Markell:We've tried to evaluate them. The thing that you mentioned, Angie, about the cycles, so I'm assuming that SCN can go to two or three cycles in my region a year, so if a seed treatment's effective, probably two to four weeks, like you might expect a normal seed treatment to work, maybe it does some good on that first cycle, but might not control reproduction over the life of the soybean. And Greg, you have four cycles maybe? I don't know enough about Iowa maybe.
Greg Tykla:Yeah, four to five.
Samuel Markell:Yeah, four to five. Yeah, so there's a lot. I have limited efficacy, and I will say, I'm going to turn it over to Greg here in a minute, but I will say we're also, for point of thought, we're also trying to evaluate some of these undry edible beans, because we're concerned about that. And we don't have the genetic resistance that we do in soybeans. Greg, do you want to talk about some of your work?
Greg Tykla:Yeah, it's hit or miss is is how I could succinctly describe it. There are times when we'll see a yield benefit and when there is a yield significant yield difference it is significant enough that it'll more than pay for the product even with like $9 beans and now with beans in the teens, it definitely will. Our our problem, at least in our my personal experiments is that the rate of positive yield effects, if we do 10 experiments, it'll be like three or four out of 10 experiments that have that positive yield effect. I'm,
Samuel Markell:for the
Greg Tykla:life of me, can't figure out why it's not more consistent. So I jokingly say that seed treatments in general, and of course, Sam explained, they're so diverse, it'd be silly to say seed treatments in general, but here I am saying it. In general, when they work, they work, and they're economical, and when they don't work, they don't. And and the final thing, I know that's pretty profound, The final thing I'll say is, we have not hardly ever seen at the end of the season, a difference in nematode numbers. But they can provide early season protection, and that can translate into yield increases.
Greg Tykla:And virtually all the time in our hands, when there's a yield increase, it more than pays for the product.
Samuel Markell:Yeah, a couple more things to maybe consider about seed treatments. So, we have areas in North Dakota that we seed 20 to 50,000 eggs per 100 cc's and growers still want to try to put some soybeans in there. Maybe that's, maybe spot, if you're going to do it, maybe that's a good place to do it. But I wouldn't expect great success. You can overwhelm any of these management tools, including the resistance.
Samuel Markell:Another thing is that as far as I know, and Greg correct me if I'm wrong, I think all the companies want their products on resistant beans. I mean, nobody's selling these things as a silver bullet that you can put on a susceptible. It is an add on, it is a very potentially useful add on, but it is an add on. And then there's another thing too, and I see Dean Melvik's name here, and he would be the authority on this, but some of the seed treatments that are being used for SCN also have an effect on sudden death syndrome, and if you have both of those, it would stand to reason that your odds of getting your money back are higher. And Dean has some of the best data on sudden death that I've ever seen, so he's doing work in Southern Minnesota.
Samuel Markell:And I see his name, although that doesn't necessarily mean he's there. It is St. Patrick's Day, right? It's a little early, but you know. But if he wants to chime in, go ahead.
Samuel Markell:But I will say, I give a nod to Dean here, that his data is available. I'm sure it's on the website somewhere, but it's really solid data on SDS, and so he's looking at SDS and clearly they have SCN in those trials. If you have both of them, that is another additional thing to consider. Some of those products, the way they're packaged anyways, can have some effect on both.
Angie Peltier:So as a follow-up to that question, an anonymous attendee asks why is there a an SDS rate and an SCN rate for for some of the nematicidal seed treatments?
Greg Tykla:That's an interesting question and I think they're probably alluding to Alevo. I don't know about Saltro but for Alevo the SCN rate is half of the SDS rate. And I don't know I have always taken pride that SCN is the big bully of the pathogen neighborhood. So it's being counterintuitive that its rate is lower than the SDS rate. But I don't I don't understand any of the biology behind those two different rates.
Greg Tykla:But it is true, at least for Alevo and perhaps Saltro, that there's two different rates, one for SDS and another for SCN.
Samuel Markell:I would assume, and this is an assumption, so it's a little dangerous, but usually when the companies, especially the larger agrochemical companies, developing these products, they've got a ton of internal data, and then they usually put the stuff out in different trials strategically located. So I'm assuming that that had that data they saw was what allowed what made them develop that rate. And there is a potential that market maybe, know, was in that thinking as well, but I'm I'm assuming without seeing the internal data, that they have internal data to support that. I know what I've been involved in several different product launches and developmental rate responses and things like that in my time, particularly on the minor crops I work with, sunflowers, edible beans, and they take that data very seriously.
Greg Tykla:Angie, do I see one last question that maybe people more than one individual are interested in, it's about cover crops. Do we have time for me to give a short answer to that?
Angie Peltier:So we have reached 09:00 so for those that need to leave we thank you and ask you to fill out the survey as you leave but everyone else is welcome to stick around and we'll keep going. So please go ahead, Greg. Thank you.
Greg Tykla:Okay. Yeah. So Liz Stahl asked a question that I get it's probably the most common question I get asked over the course of a year, and that is cover crops and SCN. They're in my opinion, unfortunately, the whole discussion about cover crops and SCN got off to a rocky start, because there was an individual in another Midwestern state that begins with the letter I that did some demonstrations that showed a little bit of promise on suppression of SCN numbers with cover crops. But unfortunately, that person was extremely he was an evangelist for cover crops.
Greg Tykla:And so he was extremely aggressive in showing that limited data across the entire cover crop community as how cover crops can control SCN. And for years, I would I would start to laugh because I would get an email that would say cover crop SCN question, And invariably, I know they were gonna show me this particular PowerPoint slide that has made it as far as I know around the globe. And I don't I don't doubt that that individual's data were accurate, but there was no materials and methods. It was never repeated. It was not ever published.
Greg Tykla:And that's quite frankly, not how science works. So because of that, a bunch of university folks have started to do experiments. And the answer, and these are really controlled published experiments, the answer is mixed. They're, even the best, probably the best paper is out of the University of Illinois, And they did four years of research at three or four different sites with different experimental designs. And they found two or three cover crops.
Greg Tykla:It's usually the grasses, rye grass, annual rye, or cereal rye, that will have an effect, the suppressive effect on SCN numbers. But the positivity rate, again, it almost sounds like my seed treatment experience. It's twenty five to thirty three percent of their experiments that they detect a difference in SCN numbers. So if you're a scientist, and you get asked this question, like me, I'll say that it could provide some benefit, especially annual rye and cereal rye, but it's about 25 to 35% of the time, you are not guaranteed that you're going to get an SCN benefit. So you shouldn't put all your SCN eggs in one basket, that that's your management program to grow cover crops.
Greg Tykla:But there's still the evangelicals out there, and I apologize if I offend you, but that are just proclaiming it. So when I put out my own research data that shows mixed results with cover crops, invariably, I'll get a couple people that send me I call them nasty grams and saying why don't I make cover crops part of the standard management recommendation and the fact is, because you can't rely on it, it could be very helpful, or it could be compute completely no effect on SCN. So my final word on that is if you want to grow cover crops, you should be doing it for conservation purposes, and not for SCN management purposes. But it's not like it's completely useless, it's just not predictable on SCN.
Angie Peltier:Thank you. So not every soybean variety that's advertised in seed catalogs as being SCN resistant performs equally well. Do we know whether seed companies simply use molecular markers or their knowledge about the lineage of their varieties to predict SCN resistance or do they also conduct bioassays? And how would you guys recommend that producers try to improve their chances of selecting highly resistant varieties?
Greg Tykla:Sam, would you go first?
Samuel Markell:Sure, that's a great question and it's something that we think about. And I don't pretend to be a geneticist or a breeder, but SCN resistance is conferred by a source. So P88788 is a source of resistance. What that means is that it has, it's like a wild relative, This nasty looking sort of soybean looking thing that breeders started to try to breed into a soybean and the resistance was conferred by maybe multiple genes, multiple copy numbers of those genes. It's really complicated.
Samuel Markell:So like if you're looking at Phytophthora, for example, in soybeans, you're looking for a one k or 3c or whatever gene, it's a gene, it's a single gene, I see it's not that way. So when the breeders will breed these things in, little genes or copy numbers might not be accounted for. So what you do is you get a range of this resistance effect in the variety itself. So how they're breeding, I'm not entirely sure. I do know that there's some molecular tools being used.
Samuel Markell:I'd be shocked if they're using markers for every known thing and copy number. That would be a shocking thing to me. And then if you don't evaluate some of these things in the field, under decent disease pressure, you might not actually know the field effect. And so in my world, that's describing essentially white mold. So we have a lot of white mold up here, and we have a lot of white mold in every broadleaf crop we grow.
Samuel Markell:Seed catalogs will often say how resistant data is for white mold. When we found in some of the trials and evaluations that we've done under high disease pressure, that sometimes that's right and sometimes it's not. And it's just the ability of a company to be able to screen a high disease pressure consistently. And I don't know about you, but it seems like soybean varieties, the second they're out, they get replaced and disappear. I don't know what their lifespan is.
Samuel Markell:Some of that data just in general on those evaluations of the complex genetics, like white mold or SCN, it's not as reliable. I don't know Greg, if I hit that the way you'd want to hit that, but please add on if you
Greg Tykla:I don't have much to add. I'm gonna show my ignorance. The University of Minnesota, Jim Orff's breeding program, and Jim's now retired, so I'm about to say I don't know the current situation, but he used to work with perhaps Dean or Senyu Chen and or Seth to get some SCN data on variety. So there was a variety trial program there, and and for a while they were collecting SCN data on those varieties. I don't know the current status of that.
Greg Tykla:Now I have a dedicated effort, about 60% of my research effort is a giant variety trial that's been going on for twenty five or thirty years. And so we do three locations across Northern Iowa, three Central, three Southern, and plant dozens and dozens and dozens of cyst resistant beans to try and generate kind of some of the information that Angie was asking, how does one get this information? But sadly, I mean, it takes a huge amount of effort and so not many states can reproduce that amount of effort. Going back to the first part of Angie's question, there are some really good seed companies that are very conscientious about either doing greenhouse testing or some type of validation to make sure when they call something resistant, it's resistant. When you do only molecular markers, there's the potential for it not to be, it's just verifying genes are there, but not in necessarily a high copy number, which affects how potent the resistance is.
Greg Tykla:So that's a little less useful if they're selecting based on just, the markers. And then I think there are many C companies that buy their genetics from a couple providers, and they're taking the word of those couple providers. And so the veracity of their claims that their varieties are resistant is kind of based on what they're being told when companies try and get them to license their variety. So I don't think anybody's purposely calling a susceptible variety resistant, but I think many seed companies, the smaller ones, they're having to trust what their seed provider told them about the variety.
Samuel Markell:Greg, you've got like the world's best data set on varieties down there, and Angie and I would like to add some maturity group zero beans to your trials. Could you could you make that happen for us?
Greg Tykla:Sure. We'll have to talk about economics of
Anthony Hanson:that.
Greg Tykla:Yeah, I really wished I could expand it or find funding for a similar crew in Southern Minnesota and North Dakota, South Dakota to do that. It's it's no trivial task to do it. And I certainly understand and sympathize that for for farmers that are in states where they just aren't interested in the varieties we're evaluating. So it's got to be frustrating.
Angie Peltier:Okay, here's a good one. So Dave asks for comments from you two about the need for producers to not give up on in season SCN soil sampling or fall sampling is there a benefit to doing that still?
Greg Tykla:Yeah, hi. This Dave Key?
Angie Peltier:This is Dave Nikolai.
Greg Tykla:Oh, okay. Oh, okay. Same kind of guy. Like, yeah, so I have a tattoo that says take the test, beat the pest. And take the test means soil sampling, and I haven't had that tattoo removed.
Greg Tykla:So in fact, with the new that was the the the low the slogan of the first SCN coalition in the nineteen nineties, and it's the current logo or slogan as well, except the current SCN coalition is take the test, beat the pest, know your number. So even more emphasis on soil testing. So absolutely, you need to sample. I wouldn't necessarily get too excited about in season sampling, but fall sampling. It's just like testing your blood pressure.
Greg Tykla:SCN is a chronic health problem for soybeans like high blood pressure is, and testing will tell you if you're on the right track for managing it or not. It's part of the coalition's effort to get farmers and those who advise farmers to be more active in managing SCN. So that's an excellent question, excellent point to bring up.
Samuel Markell:Yeah, we have the North Dakota Soybean Council is very progressive in trying to help people test, and for two reasons, and actually Angie conducted this in Northern Minnesota for a period of time as well. But there's two messages that we give to the growers. The growers outside the Southeastern part of the state, the message is to take the test to just see if you've got it. We're like Iowa, maybe without quite the yields in early 90s, late 80s, whatever that was. But in the Southeast, testing is one of the few ways that you can actually see if your management tools are working.
Samuel Markell:I mean, you've got a resistant soybean in that ground, and it's just the numbers are going sky high in that season, something's not working. It means that maybe the variety is not the best, maybe the nematode is changing, and you need to switch to piquing. I mean, but don't know of another way you could really determine that unless you're looking at the looking at the egg counts in the soil sample.
Greg Tykla:Excuse me. That's excellent point, Sam. Yeah, so again, for if you're in the frontier where SCN spreading and into fields for just a few years, testing is important. And if you're an old timer that's been battling this for decades, soil testing is important.
Angie Peltier:I think the last question that we'll take unless we get any more is something that we think about also when it comes to herbicide resistant weeds. So you know as weed seeds spread as SCN spreads we're not necessarily inheriting naive populations of SCN. They most likely will have been exposed to that PI eighty eight thousand seven eighty eight source of resistance for years and years and years. So if somebody let's say in Northwestern Minnesota knows that they have SCN in their field. They've for several years now have been planting that PI88788 source of resistance and don't feel that it's been very effective.
Angie Peltier:They've been monitoring their population densities and have noticed that they've been increasing significantly over time. Is there any advantage if there is no peaking source of resistance in their maturity groups to continuing to use that PI 88,788 source of resistance or is this something that that, you know, they should just throw out?
Greg Tykla:A Sam question, yeah.
Samuel Markell:Yeah, so the first part of that is absolutely true. So got SCN from somewhere, and those growers in Iowa, they exposed the SCN to eighty eight thousand seven eighty eight for a long, long time before they set it up our way, right? So we do know that some of that effectiveness is fading in North Dakota. Now, wouldn't assume that it necessarily is as significant as in Iowa, but that is happening, we're seeing that. But with eight eighty seven, eight eighty eight resistance and the nematode changing, it's different than some of the other things where it's like a light switch, it's on or off.
Samuel Markell:So sometimes when you have a pathogen, pick your pathogen, pick your weed, whatever, it adapts to that, there's maybe a single gene mutation or something where all of a sudden that fungicide, for example, that used to be so good, no longer works at all. And we see that with multiple, there's multiple examples in North Dakota, you only have to look at sugar beets, or maybe frog eyed leaf spot in soybeans in Southern Minnesota. That seems not that way. So remember that idea that there's lots of little genes, and copy numbers, and things like that. That nematode has to adapt to a lot of different things sometimes.
Samuel Markell:It's not going to be all at once. And so lots of times the nematode is starting to reproduce on the soybeans, it's increasing gradually, right? And so the essence of that is that there's still usually some effect from eighty eight thousand seven and '88. You usually see a resistant soybean turn into a susceptible in the season, actually, don't think I've ever seen that, Craig. But you just have to be a little careful.
Samuel Markell:And then the other concept here is that if you're gonna rotate a variety with 88,788, you may in fact be rotating around those genes a little bit, because they're not all the same. So even if you don't have Peking, if you're diligent about rotating your genetics and trying to find something a little different, you may be rotating that resistance against SCN. And there will be more effective varieties than others, even if the nematode's changing a bit.
Greg Tykla:You bring up in my mind something to mention also, I'm sorry I'm going to geek out on the biology, but people might find it interesting that because SCN requires mating of males and females, there's a lot of genetic mixing. So any female's eggs that are produced on a resistant soybean, they're not a 100% able to reproduce on a resistant soybean, and that's part of the reason why of what Sam just decided or just explained. So the genetics are really complicated. Males and females mate, and it's actually good for us that not every female that's on a resistant root is going to produce eggs that can reproduce on a resistant root. If that were the case, things would go to heck in a handbasket a lot quicker, kind of like Sam described with some of the fungicides and fungal diseases.
Greg Tykla:So it's a slow process for the nematode to overcome resistance for that reason as well.
Angie Peltier:As we wrap up here, gentlemen, is there anything else that you'd like to leave our attendees with this morning?
Samuel Markell:It seems like there's a question about rotation away from soybeans. Can I maybe
Angie Peltier:Oh, sure?
Samuel Markell:Address that. Greg, you can correct me if I'm wrong. Your rotation scheme, which would be similar to Southern Minnesota, is a little different than ours. But in general, if you rotate away from soybeans, you would expect some population drop that first year and maybe an additional drop that second year. But at some point you get into the land of diminishing returns.
Samuel Markell:So we tend to see that in North Dakota. Have, we lead the nation in like 10 or 12 crops or something. And so there's a lot of diversity in crop rotation. And we can effectively knock down those numbers by spreading that rotation out a little bit. But you can't get rid of SCN, so there's really not a lot of benefit to getting away from soybean for five or six years or something.
Samuel Markell:SCN won't go away. Once you have it, you own it. And even if you could rotate away and get rid of it, you'd to keep your neighbors wind and flood water and all that stuff off the field and we know that just doesn't happen. So yeah, there's benefit to rotating and there's benefit to rotating extra year out of soybeans. Greg, is that what you see in Iowa as well?
Greg Tykla:I only see two rotations in Iowa, corn bean and bean corn. So I can't speak to rotation very well. Actually, that's not true. I also see corn, corn, corn, corn, corn. So yeah, I'll defer to you, but we see a drop in one year of corn and in experiments, a little more of a drop in two years of corn, but it'll continue to drop, but it's slower every every year after two or three years of non host.
Greg Tykla:But it depends on how bad it is to start with. If you're, you're really in a world of hurt to begin with, you might have to go away from soybeans for for many years.
Angie Peltier:There are people in Norman County which is north of where Sam is in Fargo in Minnesota that are not able to grow soybeans. Their population densities are so high. And so it's becoming a much larger issue. And so we really thank you both for your time this morning and for your willingness to share, your thoughts and data with us. And any last words before we leave here today?
Samuel Markell:Well, I really appreciate everyone taking the time to talk to us this morning. And there's a lot of information at thescenecoalition.com. It's worth taking a look at some of those videos. Can hear from growers in different spots in the country about what they're doing, what's successful and what's not.
Greg Tykla:I'd like to end with a couple thank yous. One, on the heels of Sam mentioning the SCN coalition, it wouldn't exist if it weren't for the soybean checkoff, And so all the soybean farmers that are connected to pay into the checkoff, thank you. Probably most, almost all SCN research done by universities wouldn't exist if it weren't for the soybean checkoff. So thank you, thank you, thank you so much for supporting our work. Then final thank you for Angie inviting us to have an opportunity to speak with and share information with so many people that joined up today.
Samuel Markell:Yeah, thank you everyone and happy St. Patrick's Day.
Angie Peltier:On that note, we wanted to thank our panelists today, Drs. Sam Markel and Greg Tilka. Thank you gentlemen both. Thank you all for attending this strategic farming program today. Thank you also to our sponsors, the Minnesota Soybean Research, and Promotion Council and the Minnesota Corn Research and Promotion Council.
Anthony Hanson:Well, that was a fun conversation and goes to show just how enthused some scientists get when we get together in a bunch talking about some of our favorite subjects. This concludes the bonus episodes that we have related strategic farming for now. We'll be getting back to more regular podcast episodes coming up in April, May, and then we'll be looking at more of our typical growing season episodes as well. So we'll be covering a few more such as small grains coming up in a little bit. Hopefully, folks are not getting rained out too much.
Anthony Hanson:It's been getting pretty wet here in West Central Minnesota. We definitely need it though for when it comes to our pastures, but it's definitely slowed down field work a little bit. So we'll be waiting to see if it dries out a little bit. I hope field work goes well for everyone else out there. Till then, we'll see you next time.