Seedling diseases and small grains in a wet spring
I'm Ryan Miller, Crops Extension Educator. Earlier this morning, we recorded an episode of the Strategic Farming Field Notes program. Strategic Farming Field Notes is a weekly program addressing current crop production topics. A live webinar is hosted at 8 AM on Wednesdays throughout the cropping season. During the live webinar, participants can join in the discussion and get questions answered.
Ryan Miller:An audio recording of the live program is released following the webinar via podcast platforms. Thanks. And remember to tune in weekly for a discussion on current cropping and crop management topics.
Anthony Hanson:So again, welcome to Strategic Farming Field Notes. This is a program from the University of Minnesota Extension and they're brought to you by generous support from, the farm families we have throughout the state, especially through the Minnesota Soybean Research Promotion Council funding and also through the Minnesota Corn Research and Promotion Council. So we're glad you could join us for today's session. Like I mentioned, we'll talk about small grains and also crop diseases. I'm Anthony Hansen, an extension educator in Integrated Pest Management based out of Morris.
Anthony Hanson:And today, we're first gonna welcome, Jochum Wiersma. He is our small grain specialist. Later on, we'll have Dean Malvick to talk about our, crop pathology issues we potentially wanna keep an eye out for this year. Especially both of these, we'll be talking about what's been going on with our weather situation. And, yeah, it's been kind of an interesting year.
Anthony Hanson:So, Jochum, I think to lead off, I'll ask how has planting been going for small grains here? We've kinda had a disjointed season for a lot of folks. I know some were getting their grains really early in March, and now we've been dealing with rain. It's been cooler soils. So how are things looking overall in that picture?
Jochum Wiersma:Anyway, planting progress. Thanks, Anthony. So, yeah, the earliest stuff got seeded in Southern Minh in late March, and we've been kind of at this hop and skip every 2 weeks, getting a lot of done in a couple days. So even up north, all the way to the Canadian border, the first week, got seeded and barley got seeded in that week of April 8th through 13th. Then we had some weather delays.
Jochum Wiersma:The second batch was in that April 23rd, 24th, 25th. Then we were back out of the fields again, then May 10th in that area. So if overall, I think by now most of the wheat and barley has been seeded. Oats is mostly sourdough state. That's all in the ground.
Jochum Wiersma:Especially the second planting date, there's probably gonna be some drown out because we had some heavy thunderstorms run through and heavy rain. And so anywhere there was and it came basically within 2, 3 days after seeding. And what happens then if that seed is in the imbibition phase, you'll see that that seed has just swollen up, and then with the excess and standing water, most of that seed will rot. So there's gonna be some replanting, and there's gonna be low spots where we have very thin stands. But overall, I think stands are very, very good.
Jochum Wiersma:The crop progress, the earliest seeded is indeed, well in to tillering, and it's really time to look at your weed control programs, and actually start looking at tan spot, especially if you're wheat on wheat, which there aren't very many acres. On the winter cereals, the rye seems to be the winter rye seems to be ahead of most years and has reached heading week and a half ago in the south and is starting to head in Kirkston and in Roseau. Winter rye always surprises me. It goes from, basically just there and nice and lush and green to 2 feet tall in 3 days. It looks very good.
Jochum Wiersma:Again, only in the winter cereals too. Everything came through the winter very well, despite a very open winter. The only areas where you see problems with is where there were standing water. And so I think there too, it looks very, very good. I've not seen powdery mildew or tan spot diseases in the winter cereals yet.
Jochum Wiersma:It's relatively early, but I would start looking for some of that. And the risk for fusarium head blight on this earliest headed, rye is slim to none. It's just been too cool. So I if you would ask me right now, do I need to spray my rye to suppress fajam head blight, my answer would be no. Not in the immediate future because it's too cool.
Jochum Wiersma:So then if we move on to insects, Bruce Potter already reported English grain and Birch cherry oat aphids, I think, 3 weeks ago. I've not found them all the way north, but I haven't looked very hard. And so then we come to what are the fields look like right now? On the spring serials, there are fields that are yellowing. Now that can have several causes.
Jochum Wiersma:One of them is being tan spot. And so check if you see tan if if it's indeed tan spot. Tan spot starts out in wheat as a small chocolate lesion, and that initial infection, that fungus actually produces a toxin to which the seedlings are very, very sensitive, and you'll get this yellowing, and it will be on the first leaves first. That in a way looks very, very similar to a nitrogen deficiency, which is a possibility right now because we've had wet fields, and you might get this temporary hangover of not having, you know, a little bit of demineralization, not a big root system yet, and this crop might be a little bit stressed for nitrogen. It's kinda hard to tell the difference if you're not used to looking for tan spot.
Jochum Wiersma:But if it truly is nitrogen, a little heat will do great to get the crop out of that slump. In the in the mid nineties during the wet years, Russ Severson, did some trials with basically 5 gallons of 28% over the top, kinda to get the crop out of that slump. And in those days, when he did the work over a couple years, you you had a 50 50
Jochum Wiersma:chance that it made a difference at the end of the season. The other one, because it's been relatively cool and this would pertain to very sandy soils, the mineralization really hasn't started up. And if you didn't use ammonium sulfate in your blend starter blend, you might see some sulfur deficiencies right now. The answer to that is indeed AMS. How do you tell the difference between sulfur and nitrogen deficiencies?
Jochum Wiersma:Sulfur isn't as mobile in the plant as nitrogen, so the new growth would be more yellow than the old growth. And finally, because we have aphids, we might already have seen transmission of barley yellow dwarf virus. That will give yellowing as well, but you would be able to find AFIX. And finally, yesterday, I was on a on a Zoom call with colleagues from NDSU, and there are massive flights, especially in, in Northeast North Dakota of aster leaf hoppers, which could transmit aster yellows. And that looks somewhat similar to barley yellow dwarf.
Jochum Wiersma:In both cases, if the virus is transmitted or the aster yellows has been transmitted, there's not much we can do. Unfortunately, for 8 unfortunately, we don't have a threshold for Ashley Hoppers in cereals, and so that's gonna be a little bit of an unknown right now.
Anthony Hanson:Jochum, I was gonna ask too both related to that, but then, with aphids too. What do we do for management, if at all, when it comes to you know, some folks wanna try to prevent transmission. Kinda what's the situation on how you are supposed to look at management for the aphids as well there?
Jochum Wiersma:Oh, you manage the aphid. You don't manage the BYDV. Because once they've landed and, you know, started probing plants, the the virus has been transmitted. And when, that early transmission occurs and it's, enough of the virus or, enough of the aphids or for the virus are those words that I will never be able to pronounce correctly. Those plants more than likely will stay very, very stunted.
Jochum Wiersma:Hence the the d in BYDV, stands for dwarf. So your management tactic truly is about managing the aphids, which the threshold is still 80% of the stems having 1 or more aphids, you pull the trigger. And that might coincide, this year with your herbicide program. If you do that, and you tank mix an insecticide and you also decide to add a fungicide to your herbicide mixture, If you're working with contact herbicides like, bromoxanil, expect expect some leaf burning.
Anthony Hanson:And that's a
Jochum Wiersma:It's kinda we
Anthony Hanson:talk about a lot, just mixtures and, yeah, I I just would like to remind folks, check the labels. Some things, you have different rates, different nozzles. Yeah. There's a lot more potential for issues sometimes when you throw everything in 1 batch.
Jochum Wiersma:When you throw everything in 1 batch, you're basically loading up on a lot of surfactant, then you're gonna see more crop injury. And then finally, because we've had 2 varied almost 3 very dry years, some of this yellowing is actually herbicide carryover even if and when you follow to re cropping recropping restrictions. Why? Well, herbicides need to be metabolized by the microbial in the soil, and they need water. And if you hadn't had water and we've had very dry falls, there is a potential for carryover on some of the herbicides.
Jochum Wiersma:Authority, outlook, any a couple of those that a lot of people use in beans. Might this year give us carryover issues.
Anthony Hanson:And So you'll come I got a question for you. So Bruce Potter has been doing some of the monitoring, black cutworm, 2 armyworm monitoring networks. And how are things been up there for armyworm? Kinda what's the concerns about that one when it comes to our small grains?
Jochum Wiersma:Angie, Bruce, you wanna jump into that one? And then Bruce also talk about updated thresholds for aphids from NDSU.
Bruce Potter:Well, last weekend, in Roseau County, we're working on a project up there with, for the grass seed production trapping using pheromone traps for, true army worm. We've got a network kind of through the, through the southern part of the state as well, but they had some huge flights come in over the weekend, and it just kinda nicked that northwest corner of the state. And I'm wondering if that might not be the same system that brought, brought aster leaf hoppers up in the in the northeast North Dakota. It's cut there those those army worms came from a different area and a whole different system that hit what hit most in Minnesota. And then on the on the thresholds, there there's an, they went through some data and kinda redid, did the thresholds, and I know North Dakota is using these now.
Bruce Potter:And they're and from vegetative through head emergence, they're looking at 4 aphids per stem. And then through anthesis, it's 4 to 7 aphids per stem. And from anthesis to milk, 8 to 12 per stem. And then from, mid dough to early dough, it's 12 acres per the per stem and then cut things off. What they what they did when they looked through that data is there was more yield loss, later than than they originally had had thought.
Bruce Potter:So but 80% is gonna be pretty close to yoga.
Jochum Wiersma:Yeah. Wait 4 days and you go from 1 8 foot per stem to, you know, 4 to 8 8 foots per stem. So
Anthony Hanson:Alright. Jochum, I have one last question for you before we move on to Dean. Another insect question, but grasshoppers, you've talked about those a lot each year, especially in our drought conditions. Do you wanna give people just a little reminder of what we've been dealing with in the past and what we're hopefully seeing this year with all this rain in the spring?
Jochum Wiersma:I hope they all drown. I'd I'd again, on at the NDSU conference call that I was part of the first reports of, grasshoppers emerging, had come into North Dakota State. As far as small grains, you know, nick them early and in the edges of the field when there's still little nymphs because that's gonna be by far the easiest way to take care of them. And the threshold off the top of my head, Bruce, correct me if I'm wrong, it's 6. Right?
Jochum Wiersma:Or is that armyworm? 4 to I can't remember. I have to look it up.
Anthony Hanson:We'll have a, crop news article posted too where we'll get the specials. Yes. And those are hard to recall offhand. I I can have you, Yoakum, jump in later if you want to just mention that on the air here. In the meantime, unless you think of anything else, I think we'll move over to Dean to talk about kind of our overall crop pathology that's going on here especially in a wet spring like this.
Anthony Hanson:So Dean I'm going to pose the same question. We've kind of had this disjointed planting season. Some seed has been in the ground for months now. What's kind of the stresses we're looking at on those versus, some that was planted maybe, let's say, around Mother's Day or so just about a week ago?
Dean Malvick:Good morning, everybody. Yeah. There's different ways to to think about this. Right? The crop is at there are lots of different levels of emergence or nonemergence and growth.
Dean Malvick:And so I'm, you know, I'm mainly working and thinking about corn and soybean diseases. So, you know, the longer the seed is in the ground, especially when it gets warmer, the soil gets warmer, you know, the higher the risk of direct rotting of the seed, you know, attacked to to that seed by multiple different soil organisms. So, you know, we don't see that a lot, I don't think, unless it's very, very wet. You know, most of our seed has has high high high vigor, high germination rates. It can grow and get out of the soil pretty fast when it's warm.
Dean Malvick:And if it's cold, you know, they often can sit there for a long time and still be viable for quite a long time, I think, as a lot of you see. The thing I think about here is, you know, with the wet conditions, it brings on a situation where we might see problems with seedling diseases that we don't see normally, or at least not on such a wide scale like we might be seeing, you know, now. That's not to say we'll have large scale problems. Right? Because even when we have ideal conditions, we always don't see a tremendous amount of disease, but I expect there'll be problems.
Dean Malvick:And, you know, back to, you know, the wet weather, you know, that's certainly one of the concerns. We know that's associated with greater risk of of diseases. And that that sort of leads into 2 different situations. 1 is the problems that are now, you know, affecting the seedling or the seed growth now. But, also, think about this is also setting up some infection and some situations for diseases that will occur later.
Dean Malvick:And, for example, SDS, that syndrome on soybean. You know, it's pretty widely, thought, and there's a fair amount of data to say that a lot of the infection occurs in the very early stages of seedling growth, maybe even before emergence when the radical is just, you know, an instituting just long even maybe. And that infection ultimately leads to further development of SDS throughout the season. And if we miss this early season infection of SDS and other diseases, we may not have just a problem later. Whereas this year, we might have more infection now and see more problems later.
Dean Malvick:But that doesn't mean that we automatically will. It still depends on the weather that we have, you know, in June July. So now to back up to the seedling and seedling disease issue that we might be experiencing now. Now this is a really good time to scout fields to see what is happening. Looking at different levels of of of height, discoloration, missing plants.
Dean Malvick:Right? All those things. And that's not only disease we know that causes those problems, but that's one of them. And, again, we have optimal conditions that we can see situations that we may not often see. You know, given for example that we are so widely using seed treatments with many different active ingredients, this would be a good time to find out how well they're working.
Dean Malvick:If they're not working adequately, maybe look at what that treatment is and see what it has or what it doesn't have and see what might be optimal for another year because this will help us understand what key problems might be in different fields in different areas. And so I guess I'll I'll kinda stop there, but, Anthony, you can go on.
Anthony Hanson:Yeah. I'm just wondering what other what are our key seedling diseases in our corn and soybean? A lot of folks, you know, sometimes, especially in our drier years, we've had either we've forgotten about them a little bit or some haven't really looked into them as much.
Dean Malvick:Yeah. That's that's a good question. I I would say, you know, often we think of the big four, which would be pythium and phytophthora, which are oomycetes, and then rhizoctonia and pudestarium. Now those aren't the only ones, but if we didn't have those, I suspect we have very few problems in most fields. And so the are the oomyces.
Dean Malvick:Again, the the pathogens that really love very wet soils typically. And so that's favorable now, of course, in many fields. Rhizoctonia, it likes warm moist soil. It doesn't need saturated soil. Doesn't necessarily like saturated soil.
Dean Malvick:It likes warm moist soil. So in those years when we have delayed planting and wet soils, warm soils, where we have a bigger problem with rhizoctonia. And fusarium, there are multiple species that infect both corn and soybeans. Now I mentioned these baby 4, all of them, or some variation of them, it can cross between corn and soybeans. Phytophthora does not.
Dean Malvick:That only affects our main Phytophthora, soji, that affects soybean, only infect soybean so far as we know. So those would be the main ones. And all of them could be active now with with us being at this time of the year with these soil temperatures and with that level of moisture.
Anthony Hanson:So you mentioned, scouting earlier. For a lot of these diseases, you can pick out, which ones are kinda different in the setup. But how many of these are we just going out and scouting and making replant decisions and hopefully having a good crop if we have issues there versus, primarily just relying on seed treatments or other methods? Kinda where does that stack up in terms of what, I guess, tactics are recommended based on our key diseases there?
Dean Malvick:Mhmm. Well, you know, all of them can kill cedar seedlings at at this stage when they're emerging or soon after. And oftentimes, they don't, and they may cause something later on. You know, if the plants are surviving, we basically would typically rely on them pulling through, I guess, we could say. You know, if they're being killed, we'd lose large parts of the stand.
Dean Malvick:That, of course, is when we think about, you know, replanting. Hopefully, we don't see much of that, but, you know, certainly, it is is a concern. It could happen here and there. Does that answer your question? Were you thinking about it, Anthony?
Anthony Hanson:Yeah. Yeah. Just kinda wanted to cover a little bit, because some folks might be wondering, are they looking at replant decisions versus, yeah, maybe the crops will pull through there a bit. I should note too just, Dave Nicolai mentioned earlier just we've had obviously some heavy rain yesterday, and I did mention that at the top of the session here. But, yeah, 2 inches around Saint Paul campus, 3 at Rosemont.
Anthony Hanson:And out here in West Central Minnesota, I've had reports between 2, 3, and I think some initial glances I've seen 4 inches. I haven't seen if that's verified or not yet, but we've had quite a range here. So this is kind of the other side. It's both diseases, but then overall crop health. If you're getting 4 inches rain and you have heavier soil, what are we looking forward to in terms of kind of just longer term outlook on some of our crops here in terms of issues that we could be running into with heavy rain like
Dean Malvick:that? Yeah. That's that's a good question. You know, obviously, simply drowning, you know, lack of oxygen in the root system is is a perfectly as Bruce Potter liked to say, drowning is a perfectly good way for plants to die. So we can't always, you know, blame it on something else.
Dean Malvick:And so that's obviously a problem that occurs at times. Plants can tolerate some. There there's a limit. And, you know, for I I I don't remember what those numbers are, but, you know, for a few hours or or a day, probably they'll be fine. But if they're sitting underwater for longer, especially as the temperatures get warmer, you know, the likelihood of survival and the likelihood of, you know, good growth later on decreases.
Dean Malvick:So I guess we just have to watch it. I don't know how widespread we've had enough rain to cause significant flooding. Haven't heard about much yet, but certainly that is a a concern given how much rain we've had.
Anthony Hanson:Alright. I got 2 questions, people have asked here more from our, extension audience. One, I heard you have a Phytophthora survey that you're working on, and then the stall was wondering about, hail. If we've had some hail, is that going to introduce disease issues in these early emerge seedlings?
Dean Malvick:Okay. As far as the second question, kale, I think there's very little association that's been shown between, you know, seedling diseases and hail. Most of those seedling diseases infect through the roots or maybe the very, very low or stem, but mostly the roots. And so they don't need wounding, and they're very effective at infecting all by themselves without without a wound. So the second question was about phytophthora phytophthora survey.
Dean Malvick:Yeah. Doctor Megan McKehey in the department of plant pathology is is leading that effort, and I'm working with her on this survey trying to figure out which types or races or fat pathotypes. We call them now of phytophthora occurring at Minnesota. You know, you've heard us I think many of you heard us talk about this before. And if you look at your soybean, you know, variety trait package, you can see different genes in there called RPS genes that are effective against different types or pathotypes of phytophthora.
Dean Malvick:We're seeing more and more of those breakdown. One of the more widely used ones has been called 1 RPS one k. That's the gene that controls, you know, major resistance to Phytophthora. In many fields, that's no longer working very well. So we're trying to get a handle on how widespread the populations are of this pathogen that can overcome that gene and other genes, which can help us, you know, tailor planting and and maybe help even direct breeding efforts in the future to know what the the problems are that we have to confront.
Dean Malvick:So if there are problem fields, fields that you think there are, you know, we'd like to get soil samples. And for more information on that, contact me or doctor McKehey in the department of plant pathology.
Anthony Hanson:Alright. We'll be wrapping up pretty soon. So I have 2 questions that came in for you, unless any more come in in the meantime. So the first one, this is dealing more with cover crops, and we'll talk a lot about this both for insects and diseases. So let's, talk about the disease side of things.
Anthony Hanson:Is this helping break any disease cycles, folks that are working with cover crops? Or flipping the question around, are we worried about increases in any disease concerns in some of these cover crop situations? Anything to keep an eye out for in general, but then also this year, especially when we're looking at these wet conditions?
Dean Malvick:Yeah. That's that's a that's a very good question. Unfortunately, there's not a simple direct answer to that one. And it's complicated for a couple of reasons. It it can work both ways.
Dean Malvick:I know there was a study done in Iowa, I believe, that showed that some cut crops could increase the populations of Pythium in the soil, which could then lead to greater risk for infection of on roots of other crops. Now that second link there wasn't really shown, but it suggests that, you know, the possibility is there. And certainly, some of them are host to some of these pathogens and can propagate them and increase their population. On the other hand, we know the opposite effect can happen too. Some of these cover crops can increase antagonistic organisms in the soil that can reduce the activity and the infection by plant pathogens.
Dean Malvick:And so those are 2 kinda general general things, but it also really depends on the disease, the cover crop, and the crop we're thinking about because, you you know, obviously, there isn't just one single cover crop. It depends on which one it is and how it will affect, you know, pathogens or antagonists of pathogens. So, unfortunately, there's no simple answer. I don't think there's a lot of evidence to say it's bad. There's some evidence, like I said, to say that it it might increase the risk under some situations, and I don't think we've seen a lot of increased problems because of it, but we have seen some decreased problems with disease.
Anthony Hanson:There's a follow-up in that question, I guess. So one thing they're asking about is if you have a thick mat of rye you're planting into with soybeans, is there an increased risk for white mold? And we'll talk about that probably later on in a later session when we get to later season diseases. But for planting right now, is that, I suppose, 1, you could address just, what aspects you might have for different crops and risk with that. But then is that environment from the rye, is that contributing to anything early on, or are things broken down largely to some degree by the point we see white mold?
Dean Malvick:Yeah. So if you think about, you know, what what spurs on white mold? So it's wet conditions typically and wet soil, you know, typically in July when the soybeans are are flowering and canopy is filling. Right? And so there is there are these sclerotia, the parts of the white mold fungus in the soil that look like rat droppings.
Dean Malvick:You know, if they're near with something about an inch of the surface, they germinate and they produce this little mushroom like structure that grows up onto the soil surface, and that releases spores. Okay. If you have enough of a a plant residue mat there, it's there is some potential to disrupt that process and even the process of dispersal of the spores. If it's matted very tightly against the surface and you can see a lot of soil, I don't expect it would have much effect. But if it was covering up most of the soil with a significant level of of residue, you know, it might suppress it.
Dean Malvick:But I that's I'm I'm kinda speculating. I've not seen a lot of evidence either way, but there is some potential. But I think we need a fair amount of residue to have a really strong effect.
Anthony Hanson:Great. Well, Vicky, Dean.
Jochum Wiersma:Anthony, can I add a couple things?
Anthony Hanson:Yeah. Go ahead, Joakim.
Jochum Wiersma:K. So, Dean, and others, in cereals, underseeding with clovers has been shown to disrupt residue borne diseases, indeed, the way you described it where the the the dispersal splain splash dispersal is disrupted because you have an undergrowth, in that canopy. As far as cereals and cover crops, of course, rye is the darling of the cover crop industry and is perfectly capable of closing the green bridge for a number of our, diseases, including, weed streak, mosaic virus. And so early seeding your cover crops in the previous fall sets you up for problems the next spring to adjacent wheat fields or etcetera. Because they'll migrate the moment you do the termination of the rye.
Jochum Wiersma:The other thing is rye is very green early on, and as history has already proven, armyworms are simple creatures. They the first green thing they see, they land in. And once the rye is terminated, those armyworms are still hungry, and they'll start nibbling on corn. Or in the worst case, Anthony, I believe you found some fields where they actually started eating soybeans, which is not their normal diet.
Anthony Hanson:That was a total loss in some of those fields too. And before I forget, Yokum, Bruce mentioned, in a text here that those grasshopper thresholds, we're looking at 50 to 75 nimps on the field margins or 30 to 45 within the field, and that's for early on in the season here. So, it'll take quite a few grasshoppers to get, to those levels at least there. I think with that, it's about time for us to wrap up. So 2 things I wanna plug here.
Anthony Hanson:1st, if you are interested in submitting any disease pictures to us in Extension, look up the digital crop doc, and, we'll have a link for that and some other literature too. And, also, if you do wanna send in these samples, we do have the plant disease clinic on the Saint Paul campus. That's a good resource, if you wanna find out what's in your fields, not just for plants themselves, you can get tested for soybean cyst nematode and other, potential pathogens there. So with that, thank you again, Jochim and Dean, for joining us today here to kind of chat about what's going on and kind of this wet weather condition here we're definitely looking at after especially yesterday for most of the state. And with that again I'd like to thank all of you for attending University of Minnesota Extension Field Notes Program.
Anthony Hanson:We want to thank our sponsors again Minnesota Soybean Research Promotion Council and the Minnesota Corn Research Promotion Council.
