Field Crop Webinar Series - Emergent Pests and Diseases

March 2, 2020

Dr. Chris DiFonzo addresses crop insect problems including corn earworm and other species.  Dr. Martin Chilvers focuses on the current status and 2019 research results with tar spot in corn.  This relatively new disease in Michigan, first documented in 2016 in Allegan County, has potential to reduce corn yield if not identified and treated.

Video Transcript

- [Jim] I want to introduce Dr. Christina DiFonzo, she'll be speaking second, I'll give her the first billing on the introduction. Chris started at MSU in 1996 as a field crop entomologist and pesticide education coordinator. She holds degrees from Mercyhurst College in Erie, Pennsylvania and the University of Minnesota. Her research and extension programs focus on insect problems in field crops, including corn, soybeans, dry beans, small grains and forage crops, sugar beets, and hemp. Chris also maintains the handy BT trait table for corn in the United States, she's kind of famous for that. In addition to teaching duties and training graduate students, she provides great leadership to the extension team across the state of Michigan in field crop insect work. And Chris will follow up after Dr. Martin Chilvers who will be kicking off tonight. Dr. Chilvers holds undergrad and graduate degrees from the University of Tasmania. His research and extension programs focus on fungal biology, epidemiology, fungal genetics, host/pathogen interactions, diseases of field and vegetable crops and nucleic methods of pathogen detection. Dr. Chilver's lab at MSU studies diseases of field crops, but more importantly the biology and genetics of fungal and oomycete organisms that cause disease. They utilize classic techniques, and also the latest technologies to improve disease management by understanding these organisms, the factors and host/pathogen interactions that drive disease. Dr. Chilvers worked closely with field extension staff to monitor disease issues across Michigan, and we're very thankful to have them both with us tonight, so... - [Marty] All right, thank you Jim. Good evening everybody. Okay, so let's get started. So we're here to talk about tar spot tonight. It's another one of those, unfortunately, emerging disease across the U.S. here. All right, so let's start talking about scouting for tar spot and how to identify it out in the field. So we'll talk about distribution in just a minute. And here's a few symptoms of tar spot, as the name suggests we're looking for what appears to be flecks of tar on that corn leave. One sort of helpful diagnostic feature is that there's lesions, there's black tar spot lesions, will be penetrating all the way through the leaf. So typically you'll see them on the top surface, flip the leaf over and very often they'll be going through to the bottom side of the leaf. Occasionally we may see symptoms such as fish eye, what we refer to as fish eye symptoms. So a little bit of dead leaf tissue around that tar spot lesion itself, okay, but that's the general sort of symptom we're looking for. There are a couple of look a likes, and I know last year we did have some fields sprayed because of these look a likes, so it is important to know how to identify it and certainly if you have any questions, you know, reach out to an extension agent or somebody else that you can, or get in touch with me to help you identify things. So last year one of the things that was sprayed was insect frass, or insect poop. So, you know, that occurs fairly, or it can occur fairly early in the season, and that's what happened last year in sort of early vegetative stages and the grower was particularly concerned about tar spot setting up in his field again because he'd had a problem in 2018, so they had, what they thought was tar spot, they ended up spraying and it turn out to be bug poop. So one easy way to differentiate that from tar spot is put a little bit of water on that, if it dissolves off the leaf then that's more than likely insect frass or bug poop, but tar spot will remain on that leaf, it's really, really hard to scrape it. It's pretty much embedded in that leaf. Later in the season I think one of the other things that could perhaps be confused with tar spot common rust lesions. So very late in the season, at the start of the season there's a, you're producing orang-ish spores, you rub your thumb over that, you'll pick up those orange spores on your thumb. Later in the season those, some of those lesions may turn into a sort of black-ish color as that rust fungus produces a second spore type. But to me, I think that's a couple of sort of major ones that might be confused with tar spot. Just quickly then, this is a close up microscope image of a tar spot lesion itself, right, so we're looking side-on to the corn leaf, so that the top of the corn leaf is across the top of the image here and the bottom is on the bottom. And you can see these tar spot structures, you know, being visible on the top side of the leaf and they're protruding through to the bottom side, right, and the fungus is producing this dark melanin pigments to help it sort of survive UV light. And inside of the, these fungal structures, a whole bunch of spores that are being produced by the fungus, and you can see them being exuded onto the top left surface there, where they'll either be rain splash dispersed or aerially dispersed on the wind. In terms of the life cycle of the tar spot fungus, it's pretty simple, as far as we know. So it, unfortunately, it appears that it can survive on infect corn debris, and we've got plenty of evidence for that now. There's a couple of studies that have come out to really document that, including here in Michigan where we collected samples and proved that it was still viable after overwintering, a whole winter of season. So basically we get spores being kicked up from that debris and infecting the corn plant, you get production of more of those tar spot like structures, which produce more spores. And one of the big issues is that once a spore lands on a leaf, it can only take, you know, up to about two or three weeks before we get another tar spot structure being formed, and then release of more spores. So we've got many opportunities for multiple cycles of the pathogen during the season. And then of course at the end of the season, those infected leaves will, you know, obviously fall to the ground and potentially, you know, survive. A lot of this corn leaf debris certainly does break down, but we only need a little bit of this to get, you know, get an epidemic started again. You know we talk about cultural management, unfortunately, again, because this thing is aerially dispersed, we can do everything great in terms of having a nice crop rotation, but it's not gonna protect us from the disease because the spores can blow in from surrounding fields. Potentially many miles away, we don't have good numbers on that yet, but it looks to be quite some distance based on the rate of spread that we've seen, and I'll show you some examples of that in a minute. So when can it infect? Well it can infect any green corn leaves, okay, so this is a photo of a volunteer corn plant in September, so this is a volunteer plant that's come up in a field that was heavily infected with tar spot, and you can see some tar spot lesions starting to develop. So basically, any time that environmental conditions are suitable, and the fungal pathogen is present. Most detections in the field initiate in July but then we don't really see rapid disease progression until August or September. So this is not a new disease, so it's been around for 116 odd years or so in Latin America. So Mexico down through Bolivia. So it's, you know, it's been described for a period of time. And we've learned a little bit about the fungus from the work that's been done in these countries. But I think they've got the resources that we have, and we definitely need to do a lot more work on this, they certainly don't have it figured out down there. So when we think of Mexico, we think, generally, of you know warm sunny beaches. The tar spot fungus does not like that, right, it likes actually cooler or more mild, moderate conditions. So when we think of Mexico it's really in their winter growing season where conditions are milder, or at high elevations where temperatures are cooler. So the folks at CIMMYT in Mexico, which is an international ag research organization, looked at some of the risk factors, and this is what they came up with. Looking at, you know, Latin America there, and where they're seeing tar spot. So these sort of moderate monthly temperatures of 63 to 72 Fahrenheit, lots of relative humidity, seven hours or more of leaf wetness per night, foggy days, you know, 10 to 20 foggy days per month, and about six inches of rainfall that really, per month, that really seems to be some important risk factors for this disease. So they took that information and mapped it on the U.S. And this is what they predict to be where tar spot is gonna be a major issue. It's pretty easy to make predictions, but it's very hard to get them right, but surprisingly, you know, these guys, it looks like they've hit the nail on the head so far with, in terms of what spread we've seen the last couple of years. So here's a map of where the tar spot fungus has been recorded in the U.S. to date. So we've had our first findings of this disease in Illinois and Indiana, back in 2015. We didn't detect it until the next year in 2016 in Allegan and it was very late in the season, I think it was October that I went out and saw it with a farmer's help. The next year in 2017 we knew we had a problem because we had a field that was severely infected here in Michigan, so we knew we were going to be dealing with something. Didn't really understand the extent of it, and how quickly it would spread. In 2018 you can see this rapid sort of spread from, you know, a few counties to, you know, a pretty big area surrounding Lake Michigan there, including west and southern Michigan, northern Indiana, Illinois, and southern Wisconsin. And in some of these areas, at least in the west side of Michigan in 2018 we were seeing losses up to about 50 bushels per acre in particular fields, so we knew we had something pretty, pretty significant that had developed. And then 2019 it was much much slower to develop, probably because of the lack of rainfall during the later part of July and August. It was fairly dry in 2019 compared to 2018 where we had far more regular rainfall. The other thing you'll notice here up on the right hand side of this image is tar spot occurrences in Florida, and to date they've really only occurred in the winter growing season, again because this fungus does prefer sort of more moderate temperatures. So that's, that's the sort of extent of the spread. You'll notice as well, you know, Iowa is pretty much lit up. We've got a few counties in Missouri that are not on this current map, but, so its range has increased. The other important thing I guess, this is, this column map represents some risk, or could be thought about as a risk map. The occurrence up in Huron county, I believe that was only one field where we had a confirmation, so there's not much of the disease presence up there, so going into 2020, yes we are at risk, but at a fairly low risk in Huron, you know, compared to Allegan county where it's gonna be present, or have the potential to be present in most fields. So, you know, think about it that way in terms of the amount of risk, and through the central part of the state, even on campus here in east Lansing, we've seen the amount of risk and amount of disease increase over the last couple of years. So one of the big problems is how rapidly this disease can take off. So what you're looking at here is a disease progress curve, so just mapping how quickly disease increases in severity over time, and essentially we're in this field August tenth in September 2018, or August 2018 rather, and we had very low levels of severity. So only one of two spots on the ear leaf. We came back two weeks later and we were up to about 10%, thereabouts, you know, 30, 40, spots on the ear leaf. And by the seventh of September, the whole field had shut down prematurely, so that's what I mean by it can really sort of get away on you very quickly. Disease was first noticed by that particular grower on July eighth. Just here and there in the field. Here's some more photos of that, August twenty forth, it had moved up onto the tassels, and you can see some pretty heavy symptomology there on a husk as well. And some aerial shots of that same field, so August twenty forth you can see some browned out areas where the tar spot fungus as moved to the top of the canopy. So in the course, you know, leaf death along the top there, and that same area that was heavily effected ended up lodging as well. Because this disease also effects stalk integrity, unfortunately. It can also impact silage, we had some questions about this when it first showed up, and so what we did here is just took a sample from this heavily effected area this sort of central part of the field, lower part, and then compared it to this other area of the field that had a little bit less disease. And you can see on the right hand side of that video, there's nothing left of that stalk integrity in this area that had very heavy disease pressure. So here they are up close. In the less affected area it still had tar spot, but the stalk still had goo integrity to them, and that severely affected area, there's just something left of the stalks, right, so the stalk integrity is completely gone. We took samples from both of those locations and just looked at what does this mean in terms of corn silage quality? Obviously the moisture is shot in that area that had had basically senesced and fallen over, right, it was very dry at 19% moisture compared to about 52% in that less affected area. But unfortunately, you know, the fungus is probably using a lot of the corn sugars and leaving behind a lot of the non-digestible components you don't necessarily want to, you know, increase in the ration to your cattle. So it's increasing the non-digestible component of the feed and potentially lowering the energy score of that feed, so it's effecting the feed quality. One piece of good news is that there's no associated mycotoxins with this particular disease, so we don't need to be worried about mycotoxins like we would be if it was infected with something like gibberella ear rot where we're also have that concern of mycotoxins. So how do we go about controlling this disease, right? So, like with all other diseases, we really want to try and start with selecting a good hybrid that's got a good resistance package, right, that's really gonna be sort of fundamental to controlling this disease. We'll talk about some other components too. Here's a nice image that was provided to me to sort of show you some differences, pre stock differences between hybrids there. We did do some ratings of the Allegan performance trial site over the last couple of years now. So the amount of tar spot severity, how severely infected they are is shown in the blue bars, and the orange bars are just showing you how much, how green the canopy was, right? So we've got some varieties with very little tar spot that look nice and green, others with a lot of tar spot there that there's not much greenness left of the canopy, right, so it's prematurely killing that canopy. So two messages from this. Unfortunately there's no variety that has immunity to this disease. There are some varieties that have better partial resistance or you might potentially call it tolerance to disease. There are certainly other varieties that are a lot more susceptible. So at this point in time we want to really identify those that are very susceptible, try not to plant those in areas of high risk and really try and select material that's more resistant to the disease. It does take a while to develop new hybrids, right, but thankfully there is differences in the varieties that are out there now. So it's important to go talk to your seed dealer and figure out what they know in terms of trying to select varieties that have pretty good resistance to tar spot. We looked at a couple other ergonomic practices. One of those was nitrogen fertility. So we looked at 80 pounds of nitrogen, 160 and 240 as a side dress of urea to see if that might effect tar spot. Here's the amount of disease that we saw. The susceptible variety here on the right had more disease than the more partially resistance or tolerant variety. But we no real trend in terms of the amount of nitrogen and how that drove disease. So at this point in time, don't change fertility practices, do what you should be doing for good corn production. We also looked at planting population. So typically if we're thinking about other diseases like white mold in soybean, a high plant population that might potentially drive disease, right? So we went from 46000 plants per acre down to 28000 plants per acre. The results were somewhat surprising. In the low plant population, we actually saw more disease recorded on the leaves of those plants compared to that high plant population. We don't fully understand exactly what's driving this at this point in time, right. And I think the real message here is don't change plant population either, yet. We're gonna investigate this more this coming season. It might be something to do with air movement, rain splash, we're not sure exactly, or even lice. It certainly makes sense with other observations, when we walk into a field and there's some planting skips, we very often see a little bit heavier disease in those areas where the canopy is opened up. So it tracks with what we've seen, and again the most important thing to do is to try and identify a more resistant variety and try and avoid those varieties that are more susceptible to disease. So, in terms of cultural management practices, you will potentially be at slightly higher risk if you're corn on corn, and you're no-tilling because you will have corn debris in that field, obviously, to potentially initiate that infection a little bit earlier. But having said that, just because you're rotating fields or you're burning all of that stubble, or you're mobile plowing, does not mean you escape risk of that disease. And in that very first example I showed you, those photos of disease, that was under a two year rotation, right, and we saw a 50 bushel loss there. So unfortunately, you know, plowing, rotation, don't eliminate risk. We've even seen virgin corn fields develop very significant tar spot because again this fungus can blow in from outside, okay? Irrigation is a very very strong driver of this disease, and for those people that are listening that might be dry land producers that's fine but listen to what I'm saying 'cause this is still important if we get a lot of rainfall events, right, simulating irrigation. Here's a planting map, right, of different hybrids that are out there, and what I'm trying to emphasize here is the dry corners compared to where we've irrigated. So again this is 2018 where we had a lot of precip during the season, and where the pivot was run, we saw an additional, you know, 40, 50 bushel lost just due to irrigation, right, you can see the effect on either side. They're much smaller ears where we're, where we ran the irrigation compared to those dry corners, okay? And that's, that's the same hybrid. You can see from the planting map there's that strip of green other variety perhaps is more resistant or it's just a later day maturity hybrid, I'm not too sure and it doesn't really matter. But what was driving this was the irrigation. Again in 2018 we had a lot of precip, right, so you can see that in those blue bars. And precip, natural precip that was occurring and the irrigation was only run a couple of times to run that, or to drive that 50 bushel loss. So again, you know, irrigation can really play a role here and we want to be mindful of that. Here's another example in 2019. And it's very obvious where the irrigation is run, right, you can see it to the line. So yes we lost disease, or lost yield, sorry, to disease, but 2019 was very different to 2018. It was a lot drier during mid July and August, and so we really needed to keep that irrigation running, even though we're driving disease, right? So apparently Dan was telling me that under the pivot there we were seeing about 225 bushels per acres. The dry corners were down to about 185, so obviously, even though we're driving disease here with the pivot, we needed to water those plants for normal plant growth. And just another point here, when we switch over to talk about fungicides, this whole field had an application of Headline, Headline Amp at silking, right, so, a single fungicide will not, you know, eliminate this disease. It's not a, you know, not a silver bullet. It'll certainly help suppressing the amount of disease that develops but there is no silver bullet. And just in terms of irrigation management, we want try and avoid frequent, light irrigation events. The more you wet that canopy, the more likely you are to really, really drive disease. The other sort of anecdotal information we have here as well is running the pivot at night to maintain a leaf wetness for a longer period of time will potentially, you know, drive disease favorable conditions. So, if it is possible, it'd be better to irrigate, perhaps starting very early in the morning when we might have dew set in, and then, you know, through to the day time, and allow that canopy to dry off. The other thing to mention here if we are irrigating the potential of chemigating. So the corn canopy only holds about seven one hundredths of an inch of water, right, so it's not much water. If we're gonna but chemistry fungicides through the pivot, we want to run that pivot pretty quickly, about one tenth of an inch, putting down, to get that chemistry up into the foliage and not wash it into the soil. We want to also make sure we got our back flow prevention valve to prevent any chemistry contaminating ground water. And we want to make sure we've got uniform coverage too when we're running that pivot for chemigation. We don't have much data on that, we're hoping to set up some trials this coming season to look at that grower set up. Something else if you're irrigating, you know, we might want to think about dorp nozzles to try and reduce leaf wetness. Obviously that wouldn't, then, be a good fit for chemigate because if we're gonna chemigate we want that product all across the foliage, but it could be an option to try and reduce the amount of leaf wetness and I think that would help to reduce the amount of, obviously, leaf wetness and reduce the amount of disease driven by that leaf wetness. I'll switch over now and talk about fungicides here. This is an aerial image of the variety and fungicide trial we set up Allegan last year. There are a number of fungicides now that are labeled and others that have emergency exemptions, and this list is being updated pretty regularly. So we planted this trial June third, out in Allegan, we put our fungicides on for this one trial at R1 on the August seventh date. Disease, you know, for the trial purposes, unfortunately disease was pretty slow to get going, so we didn't see any disease until a day after spring, right, we saw one lesion in this 10 acre field that we were able to find. Most of our ratings took place in late September and early October when disease really started to kick up. But even with disease being so late, we had plenty of reports this last season of it effecting stalk integrity. So that's something else to keep in mind as the disease sort of spreads across the state. So here's some ratings. This is one month post fungicide application. So our untreated check is here on the very left hand side, right. A couple things I want to point out, the scale for the amount of disease actually goes up to 100. So we're not even hitting point one, right, so it's a very, very low amount of disease. But what we can say is yes, those fungicides are able to reduce that amount of disease, right, one month after application. We look at this same data set two month after application and we're not seeing much, those, you know, as many significant differences, right? Because those fungicides are starting to wear off, the fungus is starting to infect those corn leaves now, so just something to keep in mind. This particular trial, unfortunately, we lost under two foot of snow. We had another trial in there, so here's another trial that we looked at with some different products. And this is looking at the area, or the disease progress of the entire season. So some significant differences there, and then we'll flick over to yield here. So this is our yield data, and so some significant differences there in terms of yield, okay? This is just one, one trial. I wouldn't place a whole lot of weight on these particular results, we like to look at a number of different trials. And we are coming up with a fungicide efficacy chart together with other universities where we're comparing all these different trial data sets together, and I think that's really important to do. But the point is here that, you know, mixed mode action fungicide can really be helpful in reducing the amount of disease. I think the more important thing is the actually timing of that fungicide. So this is a trial that we set up to figure out the best timing of that fungicide. So we just used Trivapro, 'cause at the time it was the only thing that was labeled, and we looked at V6, V8, V10, VT, or an R2, or combination applications of V6 plus VT. And here's the results from that and again this is the total disease of the whole season for six different locations combined. So it was Wisconsin and Illinois, Indiana together with that Michigan location. So you see the non-treated, really no different to our V6 application, right, so this indicates to us that V6 is just gonna be really too early for most tar spot management applications. We had some with a model that we're trying to develop there. That model triggered at about the V6 to V8 growth stages, that's really showing no different. V8 you're starting to see a little bit of reduction in disease, not significantly different. But at V10 we start to see some reduction in disease, right. But the best timings in 2019 were for VT to the R2, okay, so, I think that's probably gonna be most of the timings going forward for the optimals for the applications. Somewhere in that VT, R1, through to R3, maybe a little bit later, okay. Again, if you're looking for fungicide efficacy data, this cropprotectionnetwork.org, we're gonna put some new PDFs up there, and we have some other information on tar spot up there as well, including the impact on variety and yield loses back in 2018. I did want to share this slide set that Jason Roth from Winfield was kind enough to share with me. Typically, you know, I wouldn't think that an R5 application would be, you know, would see a return on investment, right? I do want to point out that this is very particular to last year, and the disease conditions that developed in that particular field, right, I can't stress that enough. But it's a very interesting data set nonetheless. And I think really what this speaks to is when tar spot was developing in the field. And I think that's gonna be really important if we're trying to optimize that fungicide timing. We really want to get in just as the epidemic is starting to get going. Not too early and obviously not too late, right? So this is a field that was an irrigated field down in Niles, MI. They had sprayed the entire field with Trivapro at the R1 growth stage, and again, like our particular study, it might have helped a little bit, but it's probably just too early, okay. 'Cause they didn't see disease, really, until about the R5 growth stage. And I want to be careful here as well, we're talking that very early dents, right, we were just seeing some kernels start to dent, and we'll touch on that at the end here in terms of dry matter accumulation in kernels. So tar spot was detected on the seventeenth and it was sprayed August twentieth with fungicide. Jason set up a trial by hand here, and he sprayed strips so that we could use a combine head to collect data. Unfortunately the fungicides themselves are not replicated so we can't compare between fungicides, but what we can do is look at it in terms of a fungicide versus no fungicide right because we have for replicates of that particular treatment. So this is what the trial area looked like two weeks after application, and you can see in the natural color images there, you can see where no fungicides went on, except for the R1 application of course, right, so the R5 application in the middle there, nice green band compared to where we didn't have fungicide and in that NDVI imagery it really starts to pop out even more easily to the eye, right? And then four weeks after application, again you can see that, those, you know, very obvious strips really sort of standing out. So keeping that corn canopy alive for a little bit longer post fungicide application. And at harvest, it was also visible at that point in time. So you can see the area that sprayed compared to the non sprayed area. At least at the R5 growth stage. They did feel that there was a little bit of difference in lodging too, a little bit more lodging where they didn't put that chemistry on at the R5, compared to R5, so, could be something else, but we don't have data on that. But they did collect yield data. So on average what they were seeing is around about 220 bushels where they did not spray that second application of that R5 growth stage, right. Where they did put those fungicides on at the R5 growth stage, they were averaging about 240 bushels. Looks like there's a bit of a disease gradient in the field, so it may be a little bit heavier disease pressure on the left hand side of the field compared to the right hand side, but on average it looks like they're pick up about 20 bushel yield bump, or yield protection which is obviously pretty significant. So, looking a this a little bit more carefully in terms of dry matter accumulation, it does make some sense, right, because at the R5 growth stage, at the very beginning of dent, you've only accumulated 45% of that dry matter into those kernels. So you've still got a lot of cry matter to accumulate. I would say, I guess, once we were at the half milk line, when we've already accumulated 90%, we're definitely way beyond what is likely to be a return on investment, right, because it's really getting way too late then. And we might run into pre-harvest intervals too so also something else to be very mindful of, if you are gonna do anything like this. You don't want to get too close to harvest time. But anyway it just goes to show that, you know, if the fungicides are applied at the right time to manage disease, that can be really beneficial. So, this year we're thinking about setting up some trials where we try and really develop some spray thresholds. There are some disease models that we're working on as well that will be like app based, similar to Sporecast for white mold, but we're thinking about some rules of thumb that we might go out and implement. And so these, this is something that we're gonna test this particular season. So, I think, if we have less than, you know, one in, if we have one in 1000 plants with any symptoms on them, I think that's a little bit too early to spray for tar spot, right? I think we might want to wait and watch, potentially. Again, factoring other things in. Can we actually get across those acres at some point in time or who could we have to make use of the aircraft in the area at that particular time, so something to think about. But I think in general, once be get up to about 50% of plants with some symptoms on them, then I think that might be sort of a very good indication that it's time to spray. And be mindful that this, this threshold can be reached very very quickly, right, this disease can aggress quickly. We certainly don't want to wait until the crop is heavily diseased, 'cause then, yeah, it's really gonna be too late and you're not gonna protect that photosynthetic area. But this is something I'm gonna try out this particular season, see if we can come up with a better rule of thumb, compared to just going out and spraying it at a sort of standard time, I wonder about that R1 growth stage. So that's what we're gonna try out going forward this season. Just to recap really quickly then, scout, scout, scout, that's really important to know what's going on, be in touch with your network to see what's going on in your area this coming season. Fungicide based on that scouting, most likely between R1, R3, maybe R4, and maybe in some cases R5, right, I think that's gonna be the exception, that's the rule. Most mixed mode action products will suppress disease for a few weeks, and then disease will begin to keep marching on, right, so remember they're not silver bullets. And don't forget that heavy disease severity will impact stalk integrity, so that might be something to consider in terms of harvesting. You might want to pay a little bit for drying rather than trying to pick that up. So that's all the slides that I have here for tonight and I'd be very happy to take questions. Yeah. - [Jim] Any questions for Marty? If not I have one for you. - [Marty] Sure. - [Jim] You showed a slide that listed several corn hybrids and how much green they were and how much tar spot there was, and at the bottom of that slide I think the relative maturity was noted. And just to, you know, I was looking at that and it appeared to me that the shorter season, shorter relative maturity hybrids, seemed to fair worse. - [Marty] Yup, that's a good observation, right. So I think, Jim, what might be happening there, I put that slide up, so yeah, certainly in this particular disease, right, so remember this is, well, I need to explain to you that this is one point in time that we went in and rated this variety trial for disease. So I think what is happening here, you can certainly see some of the earlier day maturity hybrids on the far right hand side here with more tar spots, so I agree with you, but I think what might be happening is because they are earlier day, I think they're just starting to shut down in general compared to the later day maturity hybrids. So I don't think it's anything to do with differences in resistance between early and late day maturity, and I'll show you an example of why I think that's the case. So, we actually have some data to show that the opposite is potentially true, right? So this is data from Wisconsin, Michigan, Indiana and Illinois, so a larger data set, and we split the early day on the right, on the left, sorry, compared to the light day on the right hand side. And we'll actually see a slightly steeper curve or line on the right hand side where we've got that longer day maturity hybrids, right? So we're at about .8, so losing about .8 bushels per every 1% increase, whereas the shorter day are only about .48, so about .5 of a bushel for every 1% increase. So, I don't think it holds true, we've got a longer window that we've got to maintain green leaf area for longer day hybrids, right, so that's probably why we see a steeper curve. What it comes down to, again, is picking a hybrid with good resistance to disease, and there's obviously a pretty big spread of diseases susceptibility for those early versus, you know, early and late, right, so that's, that what it comes back to. Identifying good resistant material. - [Jim] Okay, thank you Marty. There's another question from Steve, application of fungicide produces a yield bump compared to non treatment, but does the added 20 bushels pay for the added cost of the fungicide? - [Marty] Right, well, I mean that's gonna depend on how much you can purchase your fungicide for and get it applied, right? So I think that's really the key there. - [Jim] Okay-- - [Marty] I'd say in general we're probably, you're paying there, so, what, we say 350 corn, you make, assume it's gonna cost you 35 bucks to make the application and cleaning chemistry, it's probably on the cheap side. So 10 bushels would pay, right, under that math. So, just need to figure it out for your application costs and chemistry. - [Chris] I didn't really know what to talk about today. The word emergent made me think of coronovirus, but we won't talk about that, and I wanted to talk about some new things or things that might be on the horizon. I don't have anything totally knew like Marty does as far as disease, most of what I have is just old stuff, and, or old, older insects, and maybe like a status update of where I think they're gonna go in the next season. So everybody always asks me at this time of the year how are the insects fairing with the overwintering? And I think sometimes we overestimate what cold does to insects that are used to overwintering here. Most of the time they are just fine. So I've kind of put this little diagram together to show you where certain insects overwinter. Things like grubs, wireworms, western bean cutworm, and then the eggs of corn rootworm are all under the ground, and they're kind of like safely sleeping there without really any problems. Most of the time something like grubs will go down even sometimes eight to 12 inches. So they, they're really not effected by the, by the cold temperatures at all, and they often time have, almost like an antifreeze in place of their insect blood in order to not freeze at all. There's a few kinds of critters that actually will overwinter in residue. So something like corn borer, right now, is overwintering as larvae in corn stalks. Seed corn maggots, the actual flies, will be in the field. Slugs, as adults and eggs, will be there as well, and that's not typical of a lot of insects, but they will be right there in the field. They are above ground essentially, or just below ground, so perhaps if it's particularly cold they may be diminished. A lot of our insects are kind of on the field edges. Things like cereal leaf beetles, spider mite, tarnished plant bug, the eggs of the soybean aphid are in the treeline. Perhaps they're a little bit more exposed at that point, but again, these insects make their own antifreeze. And they're capable of overwintering here or they wouldn't already be here. For example, just something I remember off the top of my head, there's a super cooling point for the eggs of soybean aphid, and it's something like minus 20 degrees or minus 30. So unless you have an extremely cold winter where things are very exposed, I don't think we see a lot of just outright death of the insects that we have. This is a map of, showing January, and it's the temperature departure from our average and we were quite warm in January, you will remember that, we've been warm for part of February too, and that's probably, you know, our new normal, with the warming of the climate is just to be a little bit warmer. We didn't have much snow, snow is a good protector for overwintering critters, but it was warm. So the impact on survival, again, will their survival be, will the overwintering death be higher or will we have more death of the insects that are overwintering? Probably not. Our insects can handle cold, cold winters. Sometimes, being too warm though can have the opposite effect than what you really think. So insects that are overwintering sort of wake up in the spring when it gets to be 45 or 50, and they have fat reserves in their body, and they're gonna utilize those fat reserves until host plants come out. And if it's too warm and they kind of wake up too early and maybe they've been warm for too long, sometimes they can use up their fat reserves and actually perhaps survival can be lower when it's warmer coming out of the winter. We see this with honey bees often times. Bees will make it through the winter and then it'll be March and they're kind of alive and ready to go, and then you get a little bit of a cold snap, and all the sudden you'll lose your colony in March or early April where they made it all through the winter, and it's because they kind of run out of food or they run out of stores. So I don't expect anything dramatic from the insects that live here whether too much survival or not enough. I don't expect much of that at all. The one thing that we do see sometimes though is that, you know, a lot of our pest insects don't even overwinter in Michigan. So examples of that would be like true armyworm and black cutworm, potato leaf hopper, corn earworm and a lot of our grain aphids. And they are sitting in those southern states. They're, they either are kind of in a quiet state, or, you know, crops are getting planted, you know, in February in a lot of these places like Texas, so they're already finding stuff to develop on, and they will increase and then be moved north on winds in the spring. The one thing about a warmer winter, or a warming climate, is that this line where they overwinter, is probably moving north. So instead of being in Georgia to Texas, if you could overwinter in Tennessee or Kentucky, or Virginia, then you have a much shorter distance in order to get to Michigan. So maybe by having a warmer winter, the impact may be more on our migrating pests that are closer to us right now and they may arrive earlier or in higher numbers. So rather than something like corn borer, we may think about something like earworm that has come a little bit earlier in the last few years. As far as looking ahead to 2020, what could we see, some of the climate models show it's going to be warmer and we're going to have higher precipitation in the spring. Kind of sounds a little bit like last season. If we have a wet start, then you think about things like slugs that like kind of a warm, moist sort of soil. They do better in that. Some of the other kind of soil insects, when seed sits in that wet soil for a while, and then they have the opportunity to come over and begin to feed. The other thing that I'm thinking about, not so much the wet, wet per se, but weed control, because there's been a lot of issues with weed problems in the last year, and there are a number of insects that actually take advantage of that. So one that I can think right off the bat is Asiatic garden beetle. If you aren't in the southern tier of counties then you may not even have seen this insect or know what it is. But Asiatic garden beetle is this little chestnut-y shaped beetle, it's a little smaller than Japanese beetle, and the adults are gonna come out in late June and early July. They're nocturnal, so you don't see them during the day, they will fly around at night. They will lay eggs under a dense canopy like potato or soybean and they also seem to like a lot of the weed species that are becoming very common in our field, like marestail and giant ragweed. They particularly will shelter under those during the day, and as they lay eggs and these grubs grow and feed, and right now they're, in the fall and the winter they are overwintering, we know now that they overwinter as their last stage which is the third stage. We also know that a lot of second stage overwinter. So when these guys come out in the spring, they're hungry. They've got another whole stage to go to finish development, and when they come out in the spring and pupate, right before that happens, then they begin to feed. And they, the, it's odd because adults will not eat corn, but the larvae love corn. So I've shown a picture here that shows everything that they can do, we have a plant that does not look effected, we have a plant that has been, probably, fed on, root pruned so heavily that it is now small and we have gaps in the row. And if you can see close on your screen, you'll notice what look like holes all over in the soil surface, and those are the emergence holes of the adults. So they cause stand loss, uneven growth and nutrient deficiencies. And they're particularly in areas with greater than 80% sand, either fields of parts of fields, which is why we see them in southern Michigan, norther Ohio, northern Indiana. But they have this connection to weeds. These are some pictures that are taken in the past. The one on the upper left is one that Bruce McKeller took a few years ago that shows a marestail plant that have been completely defoliated, unfortunately not enough to kill it. And when you pull, when he pulled that up, if you look underneath, it's loaded with adults that are hiding out. This other pictures to the right are ones that I took last year. It shows marestail that's been defoliated on the edges of a field, and it also has queen Anne's lace, it turns out that they love that, and then down at, under the roots of these plants, we actually found pupae, which is showing you that larvae actually were developing on those plants. So there is a link with weeds and these insects. And of course, last year was like a weed extravaganza, a lot of prevented planting acres were not managed, and they look like that they were growing a crop and it was marestail essentially. And when you went out and looked at some of these fields and pulled up plants, there was Asiatic garden beetle underneath. So the risk factor here is that this is in the southern tier of counties, like maybe the first and second tier, for the most part, these prevented planting areas, especially southeast Michigan had a high amount where there was poor weed control. Marestail is a delight for this insect, giant ragweed is also preferred, and other weeds as well. Sandy fields, and if people have had a history of Asiatic garden beetle. So it's just something to look out for for the summer. Now, we've been trying to work on this insect for a few years, it's difficult to work on and a lot of other groups won't work on it, but MSU and Ohio State have actually teamed up and we did have a strip trial last year in Dundee. It wasn't in a super infested field. I would say it was moderately infested. And we had Counter, which is the old Legato phosphate, Aztec which is a pyrethroid, has a pyrethroid component, Ampex is a liquid neonicotinoid that is about to get registered, not quite yet, and then a control, and those were applied by the grower. Wherever we had insecticide, we actually found dead grubs which is the first time that we've ever seen that with this insect. We were able to follow adults by putting these, in these little cup traps with water in the bottom and the adults kind of bumble in. And we not only have Asiatic garden beetle, but this first dark bar that doesn't have anything one it, this is strigoderma which is the false Japanese beetle. Looks like Japanese beetle, very close, but it's browner. And this comes out in a mass emergence in July just for one week, and then it was followed by Asiatic garden beetle. They often co-infest the same fields. So we have these beetles coming out pretty heavily in early and mid July and Asiatic garden beetle, compared to the control, this Ampex product decreased adult emergence by quite a bit, as did Aztec and counter, and also the strigoderma, and here's an actual picture of it, that was also diminished by Counter and Ampex. Yeah, this was just a strip trial with only one long, untreated strip in the field. We're looking for field sites, especially in southeast Michigan, so if you're a grower or you work with growers who have had odd problems, they have sandy fields, and they have uneven and odd stands, we're looking for those kinds of fields to do more work in this year. And again, the link with weeds is the key here for this year because this Asiatic garden beetle is particularly fond of weedy areas, weedy margins, weedy stands. There's a couple other insects that also we think of when we think about weeds. Black cutworm and armyworm, both are migrating up here in the spring to the, say like May we start yo get them, April for black cutworm maybe a little bit later for true armyworm, and they like weedy stands. So places where we've had low growing weeds that were not controlled, organic fields, places like that. Those kind of stands then have egg laying, and then when you apply Round-up or do weed control, then these insects move on to your corn. True armyworm also likes to get into wheat, and that's not weedy it's just that there's a lot of biomass there. So these are the things that we can't predict what's gonna happen now, we don't know what the populations are gonna be, but if you have weedy fields, these are another couple of insects to actually think about. Some of the Bt corns, depending on the type of Bt corn will control those two insects, and again, good weed control is really the cultural way of not having these two insects. And you try to do good weed control two to three weeks prior to crop emergence so that, if there are insects out there, they're essentially gonna starve before the crop comes up. And there's a number of insecticides, once you do have these insects. Pyrethroids do a good job if they can be sprayed, and there are decent thresholds. So, again, we never know if we're gonna have these insects, and sometimes they can be very patchy, but with our weed control problems coming over from 2019 these could be a problem. Another thing we haven't talked about in awhile but I thought I would mention is the soybean aphid. We haven't had an appreciable outbreak since really 2005 was the last large one, and then we kind of started one in 2007 that petered out, and they do have pyrethroid resistance in the western part of the corn belt where they spray for no reason. So, just as a reminder, you don't need to spray for soybean aphid, it's a losing game. Biological control is very plentiful now. If we do get something odd that begins to happen, we have a very good threshold of 250 aphids per plant, which is essentially like the top of the plant is covered by large, green, happy looking aphids, that would be threshold. I wouldn't add insecticides, if you're going over the field for another reason, that's just a waste of money, and that's what happened in Minnesota and Iowa and places where they sprayed their way into resistance essentially. And the one thing that we do encourage is that you have good fertility. Put pot ash on the field, because the low potassium areas or low potassium fields, again, mostly sandy areas, seem to be, to get a lot more aphids. And if you do spray, if you have an outbreak, don't shave rates, don't mix up odd cocktails, don't throw a bunch of junk in the tank, just spray them with a full rate of the product that you're gonna use, and kill them. That's the best way to handle aphids, but for the most part we have had some awesome bio-control for the last 10 years essentially. Another emerging issue, also related to resistance, is European corn borer. So this is some data from the corn borer outbreak, I guess you would say, that was found in Nova Scotia. The purple line is a lab colony that is exposed to Cry1F, which is the Herculex toxin, and those all die. And the bottom line on the bottom that's green, these are populations in Nova Scotia that were found that can be exposed to essentially a lot of the Cry1F toxin and they don't die. So this is the first resistant population of corn borer to a Bt toxin. This is an odd kind of situation in this Nova Scotia area, they were planting single trait hybrids of just Herculex 1, and I don't think we have any place in Michigan where we plant single trait still, maybe in the UP, maybe in northern Michigan, I hope not, because the single trait hybrids should have been flushed out of the system and replaced by pyramids for resistance management. So I hope that none of you are planting single trait hybrids or do not, that you don't have access to them, and, 'cause the resistance risk is apparently high. And I think the last thing I just want to mention, again, with resistance, is these ear, these ear feeding caterpillars are coming back. More non-Bt corn is being planted so we're more corn borer, and we have that first taste of resistance. Western bean cutworm is resistant to Cry1F, and Vip is the only toxin left for that pest. And earworm, which has not really been a pest of field corn, seems to be arriving earlier from the south and it is resistant to a lot of things from the south. It's bringing its resistance with it. So the last two years, I've had more calls about corn earworm. So just a cautionary thing about, when you're scouting for tar spot for Marty, you know, be on the look out for more of these ear-feeding pests, and if something doesn't look right, you know, give us a call. And I'll just leave this up here for a bit. This is my email and phone number if you have locations for Asiatic garden beetle, and if you ever have questions about the Bts, we, I do keep the handy trait table and publish that, and it's always on this Texas website where you can get it for free and copy it for meetings or clients or whatever. I mean, I can't keep it, keep track of these traits, so I think it's important that we all are able to keep track of it. That's kind of, I tried to go fast 'cause I knew we were getting close to eight, but I will stop sharing now and see if there are, I see there might be a question there. So the question I'm getting are what bio-controls are most effective? And I'm assuming you mean what bio-controls for aphids. The most, the bio-control that seems to work the best out in nature are the little parasitic wasps. When soybean aphids come out and colonize soybean, even when it's really early in the season, the first ones that we see, the difference from the early, like 2001 and 2003 soybean aphids and now is that parasitic wasps are now in the system. And they're almost, they almost act like a disease. They multiply very very quickly, and they wipe the aphid infestations out very fast, and then what's left gets cleaned up by the Asiatic, not the, multi-colored Asiatic, multi-colored Asiatic lady beetle, there we go, multi-colored Asian lady beetle, and some of the other native lady beetles, and a whole host of other predator type things. So we have, I think that the wasps come in first and do a great job, and then it's cleaned up by a whole bunch of predators. What preventative measures can be taken against black cutworm or armyworm when you're planting into green cover crops? So the trick with the green cover crop, oh, if you're gonna plant green, usually we tell people to try to kill the green before the, you know, if, boy that's a tough one. Normally we would say kill the cover crop before you plant so that you, and work that in, and part of that is for seed corn maggot too, because you can get issues with seed corn maggot. Where I've seen the worst problems have been with rye. So when people planted into rye and the rye wasn't really killed and you can get armyworm. Now again, black cutworm, this would be probably more of an armyworm issue, they're being blown up from the south, so you might plant into the cover crop and see nothing, if they don't arrive. If I was doing that, I might invest in some bucket traps, and actually trap, in my area, to see what the population is doing. And if I get a huge influx of them, then I'd go out and I'd scout my corn as it's emerging and just make sure that I'm, that I need, that I do, or that I have to or don't have to apply an insecticide, and then you can just do a quick spray.

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