Entomology, Integrated Pest Management, Plant Pathology, Weed Science

Episode 16: Integrated Pest Management Discussion

Join Emily as she talks to Jeff, Nevin, and Bob about how IPM influences their disciplines of study.

This transcript has been edited for clarity. 

0:19 Emily: Hi everyone and welcome to Farm Sci-Ed,
the show where we go into the science and education behind farming. I’m Emily Stine, and today we’re talking to Jeff, Nevin, and Bob about IPM and how it interacts between their disciplines.

0:45 This will be a two-part episode, so stay tuned for the next one after this. So Jeff, Nevin and Bob, can you explain the – the core tenets of IPM and how that works within your disciplines and as a whole?

0:57 Jeff: So thinking about integrated pest management and a brief overview from an entomological perspective, that’s that’s where the original idea of integrated pest management originated was. As we talked about in previous episodes, some of the early work in the late 40s and early 50s by entomologists in California were looking at, trying to find ways to integrate ecological aspects of insect pests, biological aspects of insect pests, and their management together into more of a unified principle, which then eventually evolved into developing economic decisions into those those basic principles of IPM as well that they developed over time. And so as a discipline, generally we use insect numbers as a proxy measure to determine the injury potential of a given crop to a particular insect species, and then we use those numbers to make a decision as to whether or not we should be concerned about resulting injury – that it would be economically damaging or not. As we talked about before, if it’s going to reach an economic injury level, or or exceed it and then use those economic parameters that are incorporating insect numbers to make recommendations for producers or land managers.

2:28 Bob: Well a lot of it I think is your your definition of integrated pest management, but for me it’s where you’re using multiple sources of – like for example – to manage a disease, you’re not the uh you’re not just just sticking with one particular one, depending on one, you’re looking at an integration of multiple different isolates, or multiple different forms of management. One of – one of the examples I guess, would be the combination of genetic resistance and fungicides. Say in in a cercospora leaf spot so that’s that’s one, one particular uh example of that so it’s it’s integration of several different methods of management for a disease.

3:18 Nevin: So uh in weed, weed management you can’t really – you can like in rangeland situations, or or natural areas or when you have an invasive pest, like you can scout for those, but in an agronomic field you can’t really scout for weeds. um They’re going to emerge as soon as the crop emerges, and you know generally preceding the crop, you’re going to be winter time. So it’s very difficult to scout for weeds, so we don’t really do a weed scouting system like they would do with an entomology. And the other thing with with weeds is except for extremely rare cases, the number of weeds present in the field is always enough to cause an economic injury. And so there’s never going to be a situation where you just don’t control the weeds, so we can’t really uh scout and we can’t really, uh it’s very difficult to model um you know should you or should you not do any weed control. So you’re definitely gonna be doing weed control. So with integrated weed management, that it really is just using as many uh practices as as possible, or as needed with the goal of reducing herbicide use. So the idea is not to reduce weed control, it’s to reduce herbicide use. And that’s sort of what defines integrated weed management.

4:30 Jeff: So each of us talked about, well Bob and Nevin talked more about the – basically what we had talked about previously is the pillars of IPM, so we talked about the foundational principles which are eco ecological basis, you know the scientific basis for uh for IPM and then you have these pillars, which are the tools, tactics, and strategies that we use to to manage pests and pathogens or weeds. um You know, Nevin pointed out that, you know, in weed management it’s it’s pretty specialized, you don’t really scout for weeds – um not that you necessarily can’t – but if you did, you’d be too late.

Nevin: yeah and so and that’s what you when we do, we do scout – and you should absolutely scout – but it’s kind of uh it’s kind of a post-application scouting, so it’s not um you know if you’re walking the field before an herbicide application and trying to see like what’s up, um you know, you might have already missed the boat at that point. It might be too late. So uh it’s usually to see what failed from that that application, not to make it.

5:33 Bob: You’ve also got to remember that if you’re looking at a monocot or a dicot, you have different herbicides that if you mistakenly identify one of them, then using the wrong herbicide is going to cost you even more – You’re paying double.

5:47 Nevin: – and that’s that’s true, I mean good ID is important but for for most farmers, you’re going to have four or five peak weeds in that field, and you’ve been dealing with them for the last 20 years. So you know what’s in the field for the most part, let’s say new comes up and that’s why it’s it’s more of a “did this work? What went wrong? How can we fix it next year’s?” sort of approach to scouting unlike you know for – I think both of you use thresholds for your calculations, for many of them right?

6: 13 Jeff: not in every case you know um for a lot of our
our bt corn traits we don’t necessarily scout and make a decision before the season starts as to whether or not we’re going to use that that given tool or tactic for its management. And so, from that perspective, for insect management it is very similar to weed management growers making the decision, you know probably the year before and buying the corn as to whether or not they need a corn resistant trait or a lepidopteran trait in the corn and then planting it really just based on field history which actually is pretty similar to weed management.

Nevin: yeah.

Jeff: You make decisions based on field history not necessarily within the season.

6:52 Bob: Well, same thing with us with the root pathogens or soil-borne pathogens. You know, you know those things aren’t going anywhere. In certain fields, you may have uh running to run into several different problems that are not going to go away. And so you need to remember that the next time that that field is cropped.
Jeff: But you know, both us and plant pathology you know do have some advantages for those insect pests, where you know we we can determine either through forecasting that you might use for a certain plant disease or as an insect, you know maybe it doesn’t develop every year, but you have, it’s you know Bob: it’s not always, not always too late.

Jeff: Right yeah.

Bob : Sometimes it could be, but it’s not like the situation where you ‘re already too late.

7:37 Jeff: Where you may be able to zoom in at a particular time of the season, where you may not have to treat every year. And in the case, I think with weeds as well timing is important in terms of growth stage and

Nevin: absolutely

Jeff: things that weed scientists think a lot about in terms of the appropriate timing of the application that herbicide relative to the
physiology of the plant.

Nevin: And sometimes, we get tangled up in there. So a lot of dry beans, for example, it might not be the best time to spray an insecticide but it’s the right time to put a post-emergent herbicide in so the farmer’s going to compromise on one of those and might not be getting all the benefit or even any benefit for controlling one of those pests. And so sometimes we contradict each other as well.

8:19 Jeff: Same goes for some of the, I think – fungicides or bactericides they might tank mix um along with an insecticide, I don’t know if that happens so much with herbicides but certainly certainly uh insecticide early insecticide cocktails are not unknown, um and you you see that with seed treatments as well. They’ll try to um there are build multiple methods and strategies for you know, coating a seed with an insecticide packaged along with early season fungicide. Again a lot of those decisions I think are based on um most optimistic – most optimistically are based on field history, right, but sometimes they’re cultural decisions as well.

9:05 Emily: We’ll be continuing this talk in the next episode, asking if IPM is sustainable and their general thoughts on the topic.

Join us next time, as we continue discussing integrated pest management strategies and whether or not we think it can be sustainable. Be sure to subscribe to this channel, follow us on twitter @TheFarmSciEd or visit our website at farmsci-ed.com for transcripts and other episodes. Have a good one!

Integrated Pest Management, Weed Science

Episode 14: Weed Science IPM

Join Emily and Nevin as they discuss the differences between Integrated Weed Management and Integrated Pest management within Weed Science.

This transcript has been edited for clarity.

0:19 Hi everyone, and welcome to another episode of Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Emily Stine, and today we’re continuing the conversation in IPM in different disciplines. Today we’re talking to Nevin about integrated weed management and how it relates to integrated pest management. Nevin, can you describe the difference between integrated pest management and integrated weed management?

0:38 Nevin: Yeah, integrated pest management is something that is, is something that was invented, conceived at first by entomologists. And the idea in – in IPM for weeds, or integrated weed management as some might call it, is basically trying to use a multitude of approaches to reduce herbicide use. And so is there a way we can create different weed control strategies, uhm – such as cultural, mechanical, uhm and biological control in order to reduce the number of herbicides that we – that we’re applying. And the the thought on that is that uh reducing herbicide use may reduce cost, for farmers. uh It reduces exposure of herbicides to the applicator, which sometimes those those can be toxic or carry some sort of health risks. uh There’s environmental benefits too, some herbicides are – can leach into groundwater and cause off-target uhm injury to weeds – or uh to plants – desirable plants if applied improperly. And all these things together is a good reason why we should try to reduce herbicide use if we can. But there’s also a lot of benefits of herbicides as well. I mean, generally they’re gonna be easier to integrate into a system, so if we’re looking to uh incorporate tillage or cover crop, that might require farming a different way, uh by buying a new piece of equipment, adjusting some of your farming practices. So it’s a bit easier to integrate herbicides into the system. uhm It it it’s also could be a cost saving to add approaches other than just using other herbicide practices. So, uh it it’s a trade-off, everything in agriculture has a trade-off. But basically, uhm that’s what integrated weed management is in a nutshell. It’s trying to use diverse uhm management approaches in order to reduce the the usage or the need of different herbicides.

2:46 Emily: You’ve previously mentioned something you call “the critical period” when it comes to weed management. Can you expand on that concept?

Nevin: Yeah, so this is sort of something that I think kind of – it is the closest thing we have to what would be considered an “economic threshold” or an “economic injury level” in entomology, when they talk about IPM. So in entomology, I think what they’re trying to do is figure out at what population threshold a certain insect pest is going to cause enough injury that it’s going to be justified to use an insecticide. And if you’re insect population never gets above that threshold, then there would be no reason to uhm apply that that insecticide. And so a lot of entomology or – a lot of IPM practices based on entomology are formed on the idea of y’know, you’re going to be scouting for the pest, you’re going to be tracking the pest throughout the season, you’re going to know what these thresholds are, and and then do a lot of research to establish these thresholds and sort of guide these thresholds. uhm And those strategies in a lot of ways just don’t work for weed science. And so we uhm – we can’t really uhm, scout for a weed, so it’s in the soil – the seed’s in the soil, and it’s going to come up that next year. There are ways to sample the soil, extract that seed uhm, figure out what that seed is, but those are really difficult to do in a timely fashion and is almost always going to be uneconomical. So it it’s very difficult to scout for weeds in an agronomic setting, and uh as far as thresholds go, uhm there is always going to be enough weeds present in the soil to cause economic injury. All of the time.

There’s never going to be a situation that – I wouldn’t say never, I’ve heard stories of of high-value vegetable producers putting something like a soil sterilant on the ground that kills everything. But that’s very expensive and not very practical. But there’s rarely going to be instances where there’s so few weeds that they won’t have an economic injury.

So uhm you can’t really scout, and you just should expect that every year there’s enough weeds to cause economic injury. So then y’know, how do we sort of model or determine when and when not to control weeds? So this idea was proposed called the “critical period of weed control” which is where you do a series of experiments where you do a series of experiments where sort of half the study you control weeds, maybe for the first uh week, and then the second week, and the third week and the fourth week of the field season. So you’re gonna let uh plots be weed-free for a certain number of weeks, and then you stop controlling weeds. So you might have a treatment where you have a one-week weed-free period, and a two week, a three week and a four week. And so the longer those weed-free periods are, the less yield you’re going to lose – that’s pretty simple, that’s pretty easy to understand. On the other end, of that experiment, what you do is you let the weeds appear all season long, and then later on in the season, you start controlling those weeds. And so you’re going to start controlling those weeds let’s say four weeks after they’ve established all season and then five weeks and six weeks. And so, on the front end, you have different weed-free periods, and then on the back end you have different periods of weed control. And when you link those two values together, you can model then “okay, to preserve – let’s say – 95%, 98% of the yield potential with this crop, you need to control weeds from two weeks from planting until four weeks to harvest and early on in the year, we can let weeds grow and then later in the season we can let weeds grow as well.” So that’s going to prevent at any economic yield loss. And so that’s kind of the methods we can do with yield science as far as modeling when, when not to control weeds and so the threshold really doesn’t have to do with the population of weeds, the threshold has to do with the stage of crop production – or, certain stages of crop production that are more susceptible to yield loss.

6:55 Emily: So in your mind, should integrated weed management be focused on preserving yield, or eliminating weeds?

Nevin: That’s a good question. And uh, one of the problems with the critical period of weed control is it it’s focused on preserving yield; so that’s an economic benefit. But you’re producing all of those weed seeds, and so those weeds that you decide you can let grow for these periods, especially on the tail end, are going to produce more seeds. And so they will be contributing more weed seeds in the soil, which might create more problems in the future and it also sort of ignores all the other problems with weeds. And so we have direct costs of weeds, which is generally competition and yield loss, but there’s also indirect costs of weeds.

So, we have potential for weeds to contaminate: weed seeds to contaminate grain that we’re harvesting, or lower quality, and those may not be factored into this equation, so we might say that if you left y’know, weeds until the end of the season, you’re not having that much yield loss, but you also might be sucking a bunch of palmer amaranth seed, let’s say into your combine, which is then gonna create problems. Weeds can also be hosts for insects and pathogens, and so that model also doesn’t really take into account those issues. And so for – although the critical period of weed control is a way to model when or when not to control weeds, in a lot of ways it’s a bit too simplistic.

Additionally, this idea of waiting until y’know, two or three weeks into a season to control weeds, uhm while that may work, it ignores how a lot of our herbicides are used. And generally, in weed science, the best time to apply herbicides are going to be before the weeds ever germinate – or at least before they emerge from the soil. And so we can put on soil-active herbicides early in the year, to prevent weeds from emerging from the soil and it’s easier, generally to control a weed before they emerge, they’re gonna have less yield impact because they never actually come out of the soil, and these models sort of ignore that. And so, for a large part, this critical period idea ignores some of these issues and is simplistic for what farmers actually need to do.

9:01 Emily: So then how does integrated weed management differ from resistance management?

Nevin: So, uh one of – one of the problems with integrated weed management is that the idea is that you’re trying to reduce pesticide use – or, herbicide use. So, okay, if you throw in a cover crop, and you do this sort of tillage strategy, and maybe you plant your crop a little earlier or a little later or at a higher density, you can reduce your reliance on herbicides. And what that generally means is that you’re going to be using less herbicides. And not less herbicide, but less number of herbicides.

So, a farmer might be using let’s say, in a corn field, four to five active ingredients sometimes, so different types of chemicals to control weeds. And so with this integrated weed management does if it’s successful at reducing herbicide use, what that means is you’re going to reduce it down to two or one herbicide. And a big one that would be reduced, especially since – the the herbicide that would be then the herbicide of choice, especially after the introduction of herbicide resistant crops through transgenic technologies and gene insertion would be glyphosate. And so what you’re doing now is you’re reducing the need for these other herbicides, and you can just get by with one herbicide, let’s say, or two herbicides in large part, that means glyphosate. So what that does then is it puts a tremendous amount of selection pressure on the weeds to evolve resistance to glyphosate. And so, sometimes what integrated weed management does is it makes it – it reduces your number of herbicides you’re using so that one herbicide or two herbicides that are left are more likely to get resistance developed. And that’s a problem.

And so, in the long term, thinking about all these different strategies, you know, is the goal to reduce herbicide practices, or is the goal to preserve all these different tools? So as soon as we have resistance developed to a certain herbicide, that herbicide might not be able to be used again in that field for a very long time, potentially forever, because of those resistances development. And so, integrated weed management also seems to reflect that as well. And so, resistance management, which is a different idea, is you use whatever tools are available to spread out that selection pressure so it’s not just focused on a single herbicide. Or it’s going to be focused on several herbicides.

So the idea of herbicide resistance management is you are going to use cover crops, you are going to use y’know, tillage where appropriate, you are gonna use cultural practices, but that’s in addition to applying any – as many herbicides that are useful. And trying not to rely on a single chemical or a few chemicals a year, year after year after year. That way, you’re spreading off the selection pressure and the idea is, basically, the more diverse your management practices are, the harder it is for a particular weed species to adapt to that and become very difficult to manage year after year after year.

12:05 Emily: Do you think integrated weed management is sustainable?

Nevin: So that really depends on what you mean by “sustainable.” And uh that’s that’s a tricky term. Y’know, I like to think of sustainable meaning “is this practice gonna be something that farmers can keep doing for thirty years?” y’know – “can they keep using that?” And one of the problems, like I said, with integrated weed management, is you tend to narrow the number of herbicides you use and that’s going to place a big burden on those weeds to become resistant to that. And so in some points, I would say it’s probably not the best strategy. Using herbicide resistance management, where you are using a diversity of herbicides, along with multiple approaches, to really broaden that selection pressure probably is the best management practices for some folks. Although, it’s very complicated to implement that, because it’s very complex. And how do we take a very diverse herbicide management program, that may be costly because you’re using multiple herbicides, multiple cultural approaches, and then you have to add in other practices – your fertility, and disease, insect management, uhm it just gets to be actually quite complicated. But in some ways, I feel like integrated weed management or IPM for weeds; this idea of narrowing down the use of herbicides, over time may not be the best strategy.

13:24 Emily: Well folks, there you have it. Today we talked to Dr. Nevin Lawrence about integrated weed management and how it differs from integrated pest management within weed science. Join us next time as we talk to Bob about how integrated pest management relates to plant pathology, and we continue our exploration into integrated pest management. Find us on twitter @TheFarmSciEd or visit our website at farmsci-ed.com for transcripts and other episodes. Have a good one!

Entomology, Integrated Pest Management, Plant Pathology, Weed Science

Episode 12: August Field Update

Join Emily as she talks to Jeff, Nevin, and Bob about their research project updates.

Transcript has been edited slightly for clarity.

0:19 Emily: Hi everyone, and welcome to Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Emily Stine and today we’ll be talking to Jeff, Nevin, and Bob about what’s been going on in their fields over the course of the last month of August. So sit back, relax, and let’s go find out what they’ve been up to.

0:36 So Jeff how has your research been going?

Jeff: Well, in August in our relay study, we’ve continued to sample all the plots with the exception of the wheat only plot, as the wheat’s gone. So our continuing sampling has been primarily in the bean only and a relay treatments.

And so with that, as I mentioned previously, we’ve had some some challenges with the study that are related to these being research plots and the challenges of shared equipment related to that and timing of everything. So timing in this relay system, particularly for herbicides is important. And that post post-harvest operation of the wheat in the relay system, it’s pretty critical to get that post herbicide application on, but we have to wait for the wheat to be harvested before we can get that application out there.

So that relates to our time in August because we can see in some of those relay plots, the the weed – the weed escapes as a result of us not being as timely as we would like to in these research plots anyway to get herbicides on. So other approaches we could have taken with the research was if we would have had smaller plots we could have used a sickle bar to cut the wheat and then maybe hand harvested the wheat but our plots are quite large – 40 by 40 feet – so that wasn’t really viable option for us um and we don’t have a 40-foot sickle bar so totally out of the question but because we were using a combine, trying to simulate that at least on a small scale. We were waiting for the equipment to become available, so we weren’t able to be as timely as we would like.

But we are continuing the sample as I mentioned earlier for for insects. We had one more sampling time of of different sample types and we talked about that before; sticky cards, vacuum samples, pitfall samples, we give those another opportunity for catch in August. And now we’re basically watching the beans turn yellow, so senescence – maturity of the beans seems to be a little earlier this year, and we can see that also in commercial fields in the area. Some of the beans that got in a little earlier, particularly around the hay springs area in Nebraska are already cutting and so our research plots are following suit. They’re turning yellow and it seems like the dry beans that are in the relay treatments – uh i think we observed this last year as well – are a little bit later in the maturity timing relative to the bean only.

So if you’re out looking at our plots, you’d see the bean only plots would be pretty yellow and the pods are starting to dry down, in our relay study you might even still find some flowers out there. So quite a bit of delay in the timing, and that’s related to shade and some other factors that will be one of the many things that we’ll have to tease out and work around because delayed maturity in beans is not a desirable trait to have in a cropping system, particularly for dry beans. You ideally want to get them harvested as early as you can, but just part of the research and why we’re looking at those things.

3:54 E: And Nevin, how about yours?

Nevin: Well, August is kind of – at least for dry edible bean research and weed science – August is probably our slow month. Which is, which is nice because it’s going to get real busy real quick.

um So all of our treatments have been put out now, we’re kind of slowing down on our assessments as well. And so we’re just really maintaining plots right now and just sort of making observations. So a couple things that are happening: the dried beans are starting to turn, so uh this time of year as we get close to harvest, they start to get yellow and it’s it’s actually pretty interesting. If you’ve got a field where you’re not having any sort of pest pressure or irregular watering or anything like that or everything’s uh pretty uniform as far as your inputs go, you can you can start to pick out differences in um soil uh texture because you’re gonna see certain parts of the field which maybe have a different uh coarser texture, more sandy, not as much water holding capacity, potentially those are gonna start turning yellow a little bit quicker and so we’re starting to see that. We’re starting to see these patterns in the field where some parts of the field are turning yellow, some parts aren’t but those do actually occasionally line up with with weed control treatments as well.

So we had a couple, we had one experiment this year where we were applying a bunch of different soybean herbicides that are not labeled in dry edible bean, but we’re trying to see if there’s potential to expand a soybean label and a soybean herbicide into dry edible beans. And we’re seeing some delayed maturity from some of those treatments now that delayed maturity likely is not going to result in the yield impact but we’re going to find out but some of the plots that are now quite yellow, right next to it, they’re they’re still in the midst of flowering. And so there’s, there’s pretty noticeable differences between some treatments and so that’s sort of, just what we’re seeing now, um we’re making notes of that,. But that’s going to get teased out when we go for for yield so we’ll know what the moisture content is of those beans and that’s going to give us a comparison of of what the maturity is at that time of the year.

5:54 E: And Bob, how about you?

Bob: Well, there hasn’t been a lot of disease from any anywhere in our in our plots. We did find a few lesions um periodically, but not enough to to uh need a application of the fungicides for for a grower.

But because of the studies that we are doing, we’re trying, we will go ahead and spray; either if it’s not this afternoon, then we’re going to spray tomorrow just to test the treatments that we said we were going to use. And then um just see what happens, even though the disease has not been um has been formed in our plots very readily. And but and I still don’t understand why, but it has not done that. But it is it – but it is present, I guess. and the spore catcher thing that we were trying to use – the spornado – has never told us that has – never detected any spores. So that would be with the disease triangle, that would be one of those uh points that were taken off. Which is then what we want to do to, to to manage that and they have not been conducive for the the disease to occur to a great extent. Although we have found a few here and there.

7:04 E: Well folks, there you have it. Today we talked to Jeff, Nevin, and Bob about where their research projects are at and what’s been going on in their fields over the month of August.

Stay tuned as we continue to delve into the science and education behind farming in plant pathology, entomology, and weed science. Follow us on Twitter @TheFarmSciEd and visit our website at farmsci-ed.com for transcripts and more updates. Have a good one!

Integrated Pest Management, Weed Science

Episode 11: Weed Sampling

Join Emily and Nevin as they discuss the details about the data collected for Nevin’s palmer amaranth and dry edible bean studies.

This transcript has been edited for clarity.

0:19 Emily: Hi everyone, and welcome to Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Emily Stine and today we’re talking to Dr. Nevin Lawrence, weed scientist, about the data he collects as part of his palmer projects. So sit back, relax and let’s go find out what data nevin collects.

So Nevin, what kind of data do you collect for your palmer studies and how do you go about collecting it?

Nevin: I guess we could classify the data in two different ways. We take weed control data and we take crop performance or crop yield data and we kind of think about that in two separate separate ways. So we have the, “what is the effect of the treatment on the weed population?” and then “hat is the corresponding effect of that particular weed population as controlled or not controlled by that treatment on on the crop?” And so we divide that into two – two different groups for uh weed control data throughout the year.

Maybe every two weeks we take a visual assessment of uh how good the weed control is and the way that we we do that is we always have a non-treated check plot, um and that’s a plot where we don’t do anything. And so our normal plot size for a dry edible bean study is 30 feet long and then uh usually four to six rows and we’re on 22 inch rows so that’s either seven and a third foot or that’s 11 feet and how wide the rows are but within that those treatments, we have one that we didn’t do anything and that one will usually have no dry bean yield because the weeds completely uh took over and the crops dead and non-existent. uh And so we have a yield of zero in those plots, but we also have weeds which are seven feet tall and that’s sort of our baseline of what happens if we do nothing and then when we take this visual assessment throughout the season, we kind of compare the other other plots to that one. So we we do this on a scale of zero to 100 and then we know what zero is and then if we have a really good treatment that we’re pretty sure is going to control all the weeds in in the study design we we keep it there and that’s what we call the the weed free check and that’s going to be 100 control of the weed.

But sometimes we don’t have that option especially in these minor and specialty crops we just don’t have good herbicide options a lot of times. And so we’ll have another treatment where we will go through and have to hand weed weekly which is which is gonna be a lot of work, but we’ll physically remove the weeds all use – all season long and so that way we have a known zero percent control and a known 100 control that we can use to compare the weed – the weed control data.

Additionally, besides in that visual control which which is helpful but it’s it’s not hard data, there’s a little bit of bias in that, is we will we’ll also go through and physically count how many weeds are within each plot and we do that depending on the study. It depends on how much area we’ll count, but we usually use what we call a quadrat which is a square, rectangle piece of pvc pipe or metal and those are various sizes and we’ll we’ll stick that in the plot and we’ll generally this is a rule of thumb – that it’s sort of just arbitrary – we try to count at least a square meter per plot of plants to get that population. So we’ll count how many weeds there are, and we’ll also count what the breakdown is of species.

That’s important because if we have a a weed control plot that fails early in the year, uh or it fails to control the weeds earlier in the year, we’re going to have a lot of early to emerge weeds in that plot so kochia, lambsquarter, those are the earlier weeds to emerge and that’s going to prevent later to emerge weeds from ever emerging because there’s there’s are going to be quite a bit of competition and presence of weeds in that plot. So what we can oftentimes see is if we’re looking let’s say, at palmer amaranth control, some of our worst performing plots actually won’t have any palmer in them but not because they controlled the palmer, it’s just because there was so much early to emerge weeds in them and so these counts are important to see not only what the density of weeds are but what species are coming up and when.

So we take these several times throughout the year um you know, probably three to five times we’ll we’ll do a weed count and just to kind of give some perspective on that you know a weed-free plot as i said earlier that’s going to have zero weeds in it, but the non-treated one can have hundreds, um sometimes even thousands we’ve seen weeds within a square meter, so it’s it’s pretty difficult to actually do that. You’re – you’re gonna be spending um 30 minutes on on one plot just on your hands and knees counting those weeds. uh Towards the end of the year we’ll also take biomass in those plots as well and so what we do with that is from that same quadrat we’ll go in and we’ll – we’ll cut using a knife – a rice knife actually – it’s a knife for hand harvesting rice but we’ll physically cut all the above ground biomass from weeds within that plot and then get then weigh that per species.

Occasionally the other thing we’ll do is we’ll also go in those plots and remove seed heads when they’re mature but before they shatter.
That way we can estimate seed production too. So from a given treatment, which is you know fairly small – you know we’re seven and a half feet by 30 feet at the smallest – we could say this treatment is going to produce or it has the ability to control, you know, this percentage of the weed population but you’re looking at under worst case scenarios, you know, potentially 30 palmer plants per square meter which is quite a bit and those 30 palmer plants each can produce let’s say 50 to 100,000 seeds. and so that can give a – when you extrapolate out to a whole acre, that gives the farmer an idea of what that treatment may or may not do in their field.

Right, as far as crop information that we collect, we we do stand counts throughout the year, so we’ll do stand count at planting and then we’ll – if we have zero yield in some treatments because it completely failed to control the weeds uh by the end of the year, there might not be any dry beans in there. So we can see when that stand was lost. We also take measurements of plant physiology – so how um tall is the lowest leaf, what’s the height of the – the pod height throughout the season and that’s going to be impacted by uh weed presence. So as we have more weeds, the plants going to potentially grow taller and so we’re going to have these these physiological changes and those could have yield impacts as well. So we look at what we call yield components and so, with dry beans that would be the number of pods per plant the number of seeds per pod so in a good dry bean uh plant you’re gonna have five to seven seeds per pod and uh when we have a high weed pressure, that might get reduced to one to three and so that’s a pretty significant yield loss right there.

We also look at test weight or the um the the weight of 100 seeds and so we’ll – we’ll physically take 100 seeds out, count them out 100 and then weigh those for each each treatment. Or we’ll sometimes do a thousand seed weight counts, and what that does too is it tells us we have a larger bean or a smaller bean generally you want a larger bean um but with a lot of wheat competition that the bean actually does become smaller and then finally just yield: how many pounds or how many tons per acre or tons per hectare of dry edible bean yield did we receive in those in those treatments?

8:17 E: Why do you collect so much data?

N: Yeah uh it is a lot of data. And not only is it a lot of data, but all the data we collect uh the majority of it’s probably in the last week of the crop so it’s it’s um it gets pretty busy that time of year. But what we want to do is get a thorough understanding of how the weeds are competing with the crop and what the impacts are.

So for example, um we might measure a yield reduction, but it’s important to know what the mechanism that yield reduction is. Is it because we’re having a smaller test weight? Are we having fewer pods being formed? Are we losing stand? Are we having fewer seeds per pod? All that sort of plays into what why the yield can be reduced and dry bean in particular. And so we’re trying to understand the nature of how that competition is occurring.

The other thing is we know what the end of the season um weed biomass is and density, and so sometimes uh plots that are looking good early in the year, they’re not looking that great at the end they’re not looking much better than some of the treatments been poor all year, but the yield impacts really aren’t that bad. And so what happens, is those plots because we’ve been tracking weed density throughout the year, we know that maybe those weeds didn’t come up until July or maybe even August and we’re harvesting the crop in September. And so although there’s there’s quite a bit of um emergence it was late enough that most of the yield inputs into the crop or the physiological processes that need to occur before yield, have taken place – that have taken place before those those weeds emerge.

And so there’s a lot of things we can do to link that up and that helps us know – um you know if I get a phone call from a dry bean grower that you know “we had a huge escape of of a particular weed, uh you know it’s getting harvest season what do I do?” depending on when those weeds emerged uh we’ll we can – we can inform him that you know if you harvest now there’s not gonna be that tremendous amount of uh yield loss, or we can tell them uh yeah actually um they’ve been growing all season long you’re not going to get much out of there. We also could tell them that hey your your test weight’s going to be a bit lower so you’re going to get dinged uh when you try to sell those beans at the elevator because they’re not as large uh the quality is not as good and so that’s some other components. It’s necessary to know this that we can inform growers of what to do and what to expect from different populations of weeds and what the value of using other treat – certain treatments are compared to other options they may be doing.

10:50 E: Well folks, there you have it. Today we talked to Dr. Nevin Lawrence about the data he collects as part of his palmer amaranth studies, why he collects it, and what he can then infer from that data. Join us next time as we continue examining what goes into the research in plant pathology, entomology, and weed science. Find us on twitter @TheFarmSciEd

or on our website at farmsci-ed.com for transcripts and more information. Have a good one!

Plant Pathology, Weed Science

Episode 9: Cercospora Disease Identification

Join Emily as she talks to Bob about how he identifies Cercospora leaf spot in the field and in the lab.

This transcript has been edited for clarity. 

0:22 Emily: Hi everyone, and welcome to Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Emily Stine, and today we’re talking to Dr. Bob Harveson about cercospora diagnosis and what he looks for when trying to make a positive identification. So sit back, relax, and let’s go find out what he looks for.

0:37 Bob, can you tell me what cercospora looks like?

B: Well, it’s it’s a sort of an ash gray – it’s a lighter gray and they’re they’re oval to circular and they then they can coalesce and and really kill a large part of a leaf. They nearly always have some sort of a of a dark halo – dark brown to purple – that sort of thing. What you’re looking for, like with the hand lens, is is uh clear well they’re clear and they look kind of like cobwebs – you’ll see on the the lesion itself – you’ll see what looks like pepper pieces of little little pepper black and then you’ll see like the cobwebs and all that kind of stuff if it’s sporulating. If it’s not, then it’s kind of difficult to tell the difference.

2:27 E: What does cercospora look similar to in sugar beets?

B: Well I guess one of the things it can be is alternaria. Because that alternaria tends to be more circular and less oval than cercospora and it also doesn’t always have a border around it. There’s other several other diseases that foliar diseases like phoma that also can be confused if you don’t know what you’re looking for, and then bacterial leaf spot as well. When you have enough lesions that the bacterial leaf spot is starting to kill the the leaves, then that also can look like uh cercospora and been coalescing. And the reason that’s important to know is because the cercospora is the only one of this group that we really need to be concerned about. So if you if you mistakenly thought it was one of the other ones and made an application then you’re going to be wasting your money for that. Or if you thought it was one of the other ones and you didn’t make the application, then you also could take a hit from the pathogen that’s that’s damaging – or is cercospora.

2:27 E: How do you go about positively diagnosing cercospora infections?

B: You’re looking at the leaves you’re looking at it with with a hand lens, but honestly the only way to know for sure

in in most cases is to take it to the lab. And there’s just there’s a number of other things: you can plate it out, you can watch – watch, you know look at it under a microscope to see if you can see those spores, but it’s essentially you’re trying to make it sporulate so that you can identify it for certain with that. And sometimes it’s already doing that in the field sometimes it’s not.

2:57 E: And can you describe how you force cercospora to sporulate in the lab?

B: Something that’s called a humidity chamber is it’s just a paper towel that’s been dampened and put into a petri plate. And you just get a piece of the tissue that’s got the lesions on it, put it into that, close it up, and then it creates a really humid environment, which then in roughly 24 hours you can look at it again. It should be sporulating, then you can look at it in terms of that and and or you can put it put it onto media and let it grow out. And then in that way it would produce its uh the spores in that manner. Or you can also look at it directly uh with the with the microscope and see the spores themselves.

3:37 E: What do cercospora spores look like?

They they’re long and cylindrical, almost like a sword – a blade of a sword or something like that. It’s it’s very very long and thin.

3:50 E: How do the spores of Cercospora compare to the spores of other diseases?

B: Well it’s it’s hard to describe, but it’s – alternaria would to me look more like a club, you know it has a – it has a thin handle on it but then or more like maybe a tennis racket it’s got a bulbous end on one and then it’s got sort of like a handle on the other and with the cercospora, it would be cylindrical the whole way, like like a mop stick or something or broomstick.

4:20 E: What’s the next step after you have a positive diagnosis?

B: There’s not any kind of magic number, but I think in general, people look at this and say, “if you see three or more lesions on one single leaf then it’s time to it’s time to spray” or at least think about that. It also is important to know which part of the plant that – you’re not as concerned with it if it’s down in the lower part of the canopy as it would be up on the newer leaves, because that’s where the damage occurs. And and so then yeah because every time you look at that – you see three or four lesions, there’s probably more on the way that just haven’t formed yet.

4:55 E: Makes good sense to me! Well folks, today we talked to Dr. Bob Harveson about how he positively diagnosed cercospora in the field. We talked about what it looks like, what it might be confused with, and what he does in the lab to figure out if it’s cercospora or not. Join us next time as we go into detail on the other topics. Follow our twitter @TheFarmSciEd for updates on when new episodes are released and visit our blog at farmsci-ed.com for transcripts and other information. Have a good one!

Entomology, Integrated Pest Management, Plant Pathology, Weed Science

Episode 8: July Update

Join Emily as she checks in with Jeff, Nevin and Bob on what’s happened with their projects over the course of July.

This transcript has been edited for clarity.

00:21 Emily: Hi everyone, and welcome to Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Emily Stine and today we’ll be talking to Jeff, Nevin and Bob to find out what’s been going on over the month of July. So sit back, relax, and let’s go see what they’ve been up to.

0:41 So Jeff, how has your relay study been going?

Jeff: A couple big things going on in July in the relay study. One is we harvested the wheat. And so we brought a plot combine in, and the other big item is that western bean cutworms are flying and so those numbers are ramping up now. We’re still right around 25% emergence based on our predictive model and uh presently we’re catching hundreds every night. So we’ve got quite a collection – a couple thousand – more than a couple thousand western bean cutworms in a cage, laying eggs that we’ll use for various things within the relay study.

E: Have you run into any specific complications this month?

J: So the wheat harvesting relay this year is a bit challenging. Partly because in our research program, we share a lot of equipment, particularly expensive equipment like plot combines. And so you kind of get the equipment when you get it and this year we got the equipment a little later than we would have liked to, which meant that the dry beans were a little further along in maturity than they would normally be. What that means, is the the plants were bushier, a little bit bigger and they were starting to bud, so the flowers were just starting to form.

And so normally, last year, for example, we were able to get the combine a little bit earlier prior to – prior to budding and before the beans really had a chance to um to bush out that much. So what that meant was a couple challenges. One major challenge was because of the uh increased kind of growth, morphology, structure of the dry bean plants, they were more prone to getting run over by the combine. They get caught by the wheel and and you can knock a row down here or there. Fortunately we have really large plots, um but one thing we did do, um not only because of that sort of – what you could call “combine blight,” uh but also because they – as I mentioned – were starting to bud, some of them may have been starting to flower. That’s a fairly sensitive time for a dry bean plant. It’s more susceptible to injury at that time, mainly because those flowers can drop off. If you lose a flower, then obviously you lose a pod. You lose pods, you lose str – lose beans and so you lose yield.

So what we what we decided to do is we ran the plot combine through all the plots, regardless of whether or not the plot had wheat in it or not, just to make sure that all the treatments were treated the same – had the same potential for combine blight, if you will. So that was one challenge. We were successful in harvesting wheat off the top of the beans, the bean canopy was starting to get kind of close to the top of the wheat and there were a couple plants here and there that we clipped, and in fact there were quite a few growers and agriculturalists on Twitter that were pretty interested in us evaluating the clipped rows from the unclipped rows; partly because there’s some interest in the dry bean community and other growers, other crops as well that have similar growth habits, to try to understand what that clipping does to yield. There’s a bit of a debate on whether or not if you clip a dry bean at a certain time of the year if that promotes more branching, which promotes more flowering, so on and so forth, so we’ll probably take a few additional notes to try to account for some of that.

The other challenge was because the beans were already flower flowering, and we had to wait for the wheat to be harvested out of the relay plot. Before we could spray our first post – our post herbicide application, we were not able to apply uh herbicide in the relay plots, because the dry beans had begun to flower by the time we got the wheat removed from those plots. So so those plots will be uh not be receiving a post herbicide application. Benefit is, um in in treatments or in plots that are the relay plots where they have this cereal in it – like I, I think mentioned before – is there’s pretty good weed suppression in those plots as opposed to the conventional beans which had no residue at all – had a lot more potential for for weed development. So so we think that’ll that’ll work out okay, um but might require a little bit of hand pulling here and there.

E: Gotcha, well I hope you get some good data out of it anyway.

5:37 And Nevin, what about you? What’s been going on for you in the month of July?

Nevin: Well, July has has sort of been a continuation of June. June got very hot very early. I wouldn’t say extraordinarily hot, but it usually doesn’t get as hot as it does that early. So we were hitting triple digit temperatures uh earlier than we usually do, and July has sort of been a big continuation of that. So it’s been a very hot year and in June uh when we were planting our dry edible beans, we had a number of herbicide failures. Mostly we first noticed with our pre-plant burn downs.

So we have a few trials that are going into a cover crop or no-till and the products we use to kill that cover crop or the weeds that are present in those no-till studies, they just weren’t working. And um that’s a common experience among a lot of the people in the area. I’ve got some – I’ve been talking to my stakeholders that work at different uh agricultural service companies, different co-ops, and they’ve been having a lot of reports of herbicide failures. So that happened in June, but what we’re seeing though, is that that those failures this year um has has extended into our our soil applied herbicides, which are really critical for dry edible bean control and um we just have not been getting very good control.

And that’s, that’s a good thing actually for research. It’s not a good thing for farmers but uh we’ve got a few studies where we’re comparing uh group 15 herbicides so we’ve got Outlook, Dual, um Warrant, some of those products are labeled and dried, some aren’t. So we’re trying to see if there might be some possibility to expand the options available in dry edible beans. And we’re starting to see some separation, those products now in a normal year we wouldn’t see that separation. Everything would work pretty well but I think this year with just that – the higher temperatures um and also the increased irrigation that we need to put on to keep up with those higher temperatures, we’re starting to see faster degradation of the soil applied herbicides and we’re getting a little bit more separation in our weed control results between treatments and that’s good. You want these years, so that in normal year maybe there wouldn’t be a big difference but these extraordinary years or sometimes when you learn something.

E: Now if I’m correct, July is the month you do most of your data collection, right?

N: Data collection is pretty much what we’re doing in July. At this point, especially right now, it’s a bit later in July. We we have in the first couple weeks of July, we have sometimes – some later post-emergent herbicide applications in dry edible bean, but then we’re basically done with imposing treatments for the year. So what we’re doing now is maintaining plots by scouting for diseases and insects, sort of those lesser pests and try and keep up with the irrigation. That’s basically what July is.

But on top of that, we have data collection and right now what we’re doing is: depending on the trial we’re going out every week, every two weeks and we’re taking assessments. So visual assessments, we’re looking at the plots and just kind of making a note saying this this controlled um let’s say 70 percent of the weeds compared to the non-treated check where we didn’t do anything while this other treatment uh we’re looking at 80% control. And to kind of bolster those those ratings which are done visually, we’re also going in and taking some physical data uh and that’s mostly right now in the form of weed counts. We’ll do some more other stuff later on.

So we’re putting out specific quadrats – there’s, there’s my here’s my quadrat right there – and uh those are are laid out in the field and more or less a random method within each plot so that we’re not biased by where we’re putting it in in the plot. And then what we do is we we just count every couple weeks how many weeds are in that plot. And that gives us an idea of if there’s a difference in species response to certain herbicide treatments or if we’re seeing different types of herbicides come up at different times of year. so we can kind of track emergence throughout the year and uh we’ll be doing more measurements later on as we get closer. But that that’s been mostly what we’ve been doing.

We also have to in in certain studies we have a – what we call a hand weeded check, so in order to assure that we have a plot that has zero weeds in it. And we need the zero weeds so we know what the yield potential is of the dry edible bean crop and or other crops in absence of weed competition. We have to maintain those plots weed free and sometimes the best way of doing that is just going out there with a hoe and so we spend a lot of time this time of year going out, usually in the morning before it gets too hot, and we’re with a hoe and bent over just pulling weeds. And that’s a lot of what weed science is.

E: Hope all that went smoothly for you.

10:34 And Bob, how’s your cercospora and sugar beet study going?

Bob: Well, they’re doing fine. From a standpoint of a pathologist, it’s kind of disappointing. There’s not a lot of disease out there. We did inoculate a couple weeks ago, and the Spore-nado thing that we’ve been using, which which measures active movement of spores if they’re present, has not – uh has been zero. We’ve done this now for the three weeks, and uh there’s been no um cercospora found on the on the little discs that we see. It’s been – it’s certainly been hot and it might have been a little bit too hot, but it’s been high moisture in terms of the humidity – it’s been brutal. And it’s certainly been hot enough for that, but it’s not there. There’s apparently not any spores flying around. So we went out, and looked at that again – I mean I looked at it every week.

If we go back to the disease triangle, what we’re doing with the spore-nado is that we’re measuring to see if the pathogen is present and with the alert system we were seeing if the environment was conducive, and it’s just been off the charts from from the different sites that we have. But the fact that we’re not identifying any spores takes away that leg of the – uh of the triangle. So that the pathogen is not present so we’re just not getting any disease currently, even though we’ve tried to do everything: create a more humid microclimate, and sprinkler – overhead irrigation, it’s just not there.

And I don’t – I can’t understand why, but for some reason, they – we haven’t had a lot of evidence that the inoculation did anything. I’ve seen weekly reports of of the different sites, and they’ve really been high, which would suggest that the conditions were conducive for for disease to occur. But I have not heard of any severe outbreaks, so I – I don’t know if if that’s the case or not. But it’s that’s – that’s what we have.

E: Fingers crossed you get the results you need.

12:39 Well, folks there you have it. We talked to Jeff, Nevin, and Bob, and checked in on all of their projects and what’s been happening over the month of July. Unfortunately they’ve all run into a couple of hiccups, but for the most part things seem to be doing okay. Join us next time as we continue going deeper in their projects to find out more specifics about how and why they do the research they do. Until next time, don’t forget to like this video, leave a comment below, and subscribe to our channel for more updates. Visit our website at farmsci-ed.com for transcripts of all the episodes. Follow us on twitter @TheFarmSciEd for more updates and reminders about what we have going on. See you next time!

Integrated Pest Management, Weed Science

Episode 7: Weed Competition

Join Emily as she talks to Nevin about what weed competition is and why managing fields for weeds is important.

This transcript has been edited for clarity.

0:21 Emily: Hi everyone, welcome back to Farm Sci-Ed, the show where we go into the science and education behind farming. My name is Emily Stine and today we’ll be talking to Dr. Nevin Lawrence about weed competition and how it relates to his studies as a weed scientist. So sit back, relax, and let’s go find out all about weed competition.

0:43 So Nevin, can you explain what weed competition is?

Nevin: Weed competition is uh simply the negative impacts on fitness to a plant caused by neighboring plants of another species. And this is most easily understood in the – in the terms of crops -with crops being competed against for resources by weeds.

1:07 E: And what is it that weeds compete for?

N: Usually, when we talk about weed competition – uh weeds and crops are competing for water. So especially in – you know – dry land agriculture where you might not have enough water for optimal crop yield, when weeds are using some of that available water in the soil profile, you can have additional shortages to the crop. Nutrients, so fertilizer or just the nutrients that are naturally there in the soil, sunlight, and so you can you can have a tall plant that’s blocking some sunlight from reaching the bottom and that’s going to interfere with the optimal photosynthesis. And then sometimes also space is included in there as well – that they’re they’re running out of space because of the number of weeds in the field for a particular crop.

1:59 E: How early does competition begin?

N: So competition – uh – when we think about it in terms of nutrient or resource competition – so they’re competing for a a resource that has to occur; you have to have a limited resource for for the competition to be to be happening. So if we think about planting a crop – let’s say corn – and you’re going to put in a starter fertilizer, well the corn is not going to be using all of that fertilizer right away. It’s gonna have to get to a certain height before it’s starting to need, let’s say if you’re doing a type of farming where you’re gonna be putting two applications of fertilizer on, there’s gonna be a point earlier on the season where it doesn’t need it yet, based on growth stage, that second fertilizer application.

So there’s there’s enough fertilizer – more than enough for for – let’s say that corn plant in this example, so we can imagine early on the season uh when we’re preparing the seed bed, everything’s just perfect and the the crops just coming up, there’s probably enough sunlight, space, water, and fertilizer for all the plants that are grown in the field – including the weeds. So we wouldn’t think that nutrient competition or resource competition’s occurring right early in the field. But we also do sometimes see yield impacts from early season weeds. But this isn’t generally considered to be caused by resource competitions. Instead it’s caused by something called the “shade avoidance response.”

3:35 E: What is the shade avoidance response?

N: Plants absorb certain wavelengths of light and they reflect other wavelengths of light. The reason why plants are green is because they’re reflecting green lights; they’re not absorbing that green light. And so, when a plant is is hit by sunlight and it it sends off certain wavelengths, neighboring plants can detect the presence of that particular plant based on the reflectance or changes in the way the wavelengths of of light that’s hitting them. So in particular, what happens is plants are able to change – detect changes in what’s called the red to far red ratio.

So red light is the light that we see, far red is uh red light that’s on a wavelength that we we cannot see. And so those changes in red to far red ratio, plants can detect that and those changes occur because of neighboring plants; either the light reflecting from the plant to the soil or to the neighboring – just directly to the neighboring plant. But they can detect that.

So plants can detect the presence of other plants nearby and just the simple act of detecting those other plants nearby, causes what we what we refer to as a “shade avoidance response.” So what they’re trying to do – the plants – is they’re once they know that “okay there’s another species nearby,” is they’re going to try to grow in a way to avoid being shaded.

They don’t want to be the lowest plant in that canopy, so they’re going to try to grow taller and so this is – this is called the shade avoidance response. And what that means is the plants will actually grow taller. We can also see changes in leaf morphology – leaf morphology. So the angle that they uh are going to hold their leaves up and so instead of being – let’s say – flatter, they’re going to be more upright. They might have smaller leaves because they’re putting more resources getting tall and all these changes that occur and not just with crops but also with weed species is in response to neighboring plants. They’re trying to avoid being shaded in the future from competition. uh

And what can happen though when we think about crops is uh when they’re putting these resources into growing taller and potentially smaller leaves, they’re going to be putting less resources into other things. Particularly when we think of a grain crop – so corn, soybeans, dry beans, peas, wheat – these plants which produce grain that’s harvested, less resources are going to go into that grain and so you might have a decrease in yield just because these plant – these weeds are nearby. And these weeds are nearby and this this response can occur when the weeds are very small and at a point where they’re not actually competing for resources yet.

And so what can happen in a farmer’s field, for example, is you might control the weeds when they’re very small so they emerge uh you’re you’re – through tillage or through an herbicide application – you’re gonna, you’re gonna kill all those weed species off. But they’re present for just long enough to alter the red to far red ratio reaching the crops. And that might trigger the shade avoidance response and lead to decreases in yield or yield potential even without any resource competition taking place.

7:10 E: Can you explain how the shade avoidance response ties into your research?

N: Yeah, uh so we we just, we’ve got a couple projects we’re looking at this. But one of them is – uh – we just finished, actually it’s it’s currently being prepared for publication uh from a former grad student – Clint Bierman and uh what we’re looking for is how long you need to keep the crop weed free to preserve maximum yield. And this is a long time old concept in weed science. It’s been done for a long time, and so what you do is you’ll start weeding a plot with with a hoe; you won’t use any herbicides and so it’s a very time consuming experiment.

But you’ll you’ll keep out of the plot for the whole season and then you might start – in this case it was dry beans – so when the dry beans hit the first trifoliate, so the first set of trifoliate leaves that come up will start weeding then. So we’re allowing a few weeks of weeds to be present and the next time we might start at the sixth trifoliate. And so what we see is as you let weed competition go on longer and longer and longer the yield goes down and that’s not very surprising.

But one thing that we did with this experiment is um in half the plots we had the same amount of weed-free periods so we’re removing these weeds by hand throughout the season for different lengths of time, but for half the plots they received what we call a soil active herbicide treatment at planting and so this was a a pre-crop emergence. So before the crop emerged, we put down an herbicide that’s active in the soil and it controls weeds after they germinate. And so that’s when the roots first emerge from the seed. But before those plants emerge from the soil, and so those plants never actually come out of the soil – those weeds never come out of the soil.

And when we compare the the weed free – so the whole season we we controlled all the weeds through hoeing when there was a uh the soil active herbicide applied, which only provided weed control for about the first four weeks of the year. That yielded higher than when we came in every – let’s say uh two to three times a week – and and controlled the weeds. And so we were literally going out there with a hoe three times a week, The plants never – the weeds never got taller than a quarter inch but just that small amount of weed emergence that would happen, let’s say between a Monday and a Wednesday, was enough to get a decrease in the yield.

Now it’s not a large amount, it might have been five percent of the yield that we we got from the season long weed free with the pre-emergent herbicide, but what we’re seeing is: having this herbicide that controls weeds while they’re germinating applied at planting actually provides some yield benefits just because of the shade avoidance response. So we’re preventing through the use of herbicides – um weeds – our crops from responding to the these changes in light quality um caused by the weeds being present.

And so that’s one example is that we’re actually seeing the use of soil active herbicides applied before crops emerge as preserving yield season long even when we remove all the weeds and the other treatments. And and this this is gets related to some other products we have. So um one of the things we’re doing right now in dry edible beans, uh again with our my graduate student Joshua Miranda is we have um we have – most herbicide – most programs in dry edible
beans you apply these soil active herbicides at planting, they wear off after about four to six weeks, and then uh you’ll apply – you’ll – once the weeds come up, you’ll apply an application of herbicides that control weeds that are that are emerged.

And these treatments, because of herbicide resistance no longer controlling uh one weed in particular – palmer amaranth – in our area, so we have to – what else can we do? So what we’re doing now is we’re applying these same herbicides that are applied at planting but we’re applying them – let’s say three to four weeks after the crop emerges. And so we’re overlapping these residual herbicides and so the goal is to never let that herbicide that’s applied at planting dissipate in the field where it’s no longer providing control. And so we have this overlapping residual herbicide that’s active in the soil and we can extend that control from four to six weeks at planting to maybe um six to eight, maybe even ten weeks after planting. And so what that means, is we’re preventing the weeds from ever coming up in in the soil. And that means we’re we’re probably not having actual crop competition when we use these post-emergent herbicides but uh that control weeds that already emerged, but those treatments may not be preventing the shade avoidance response.

And not only in dry beans but I’ve – I’ve personally – there’s a number of corn products out which are, have a high amount of activity in the soil and products like Acuron, Resicor, there’s a few others as well – I’m not trying to be particular in any herbicide brand – but but those herbicides, you apply them – uh let’s say at planting of corn – and then you can apply them at V4, the fourth collar stage on corn, and and basically you’re you’re you’re keeping that crop weed free all the way up until uh pretty late in the season without ever having to control emerging weeds. And so uh this is just another argument for why these soil active herbicides may be quite a bit better than herbicides that control weeds after they emerge, because we are not only preventing competition but we might be preventing the shade avoidance response as well.

13:03 E: Thanks Nevin. Well folks, today we talked to Dr. Nevin Lawrence about weed competition and the shade avoidance response and how those two concepts tie into his research here at the Panhandle Extension and Research Center in Scottsbluff. Join us next time, as we continue to look at Nevin and the other researchers’ projects over the course of the growing season. Be sure to like this video, comment below, and subscribe for more updates. Find us on Twitter @theFarmSciEd
and visit our website at farmsci-ed.com for transcripts and other information about this program. Have a good one!

Entomology, Integrated Pest Management, Plant Pathology, Weed Science

Episode 4: June Research Update

Rather than talking to a specific researcher this episode, we thought it would be neat to see what parts of their research happens in the spring through June. Come join Emily as she talks to Jeff, Nevin and Bob about what’s been happening in their plots already.

This transcript has been minorly edited for clarity.

00:18 Hi everyone, welcome back to Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Emily Stine and today we’ll be taking a little different approach, talking to Jeff, Nevin, and Bob about their current research projects and where they’re at in the month of June.

00:34 So Jeff, how has the relay study progressed over the course of June?

Jeff: Well, the month of June has been unusually hot and dry. So, we were able to get some timely applications in the study done, so we were able to in early June – well actually early May I should say – we got the herbicide banding done for the relay plots. So our strategy this year was to use an herbicide banding technique to spray out the wheat in the relay to create small beds for the for the dry beans that we’d plant in the relay treatments. Basically, in 30 inch centers we have basically a five inch band of wheat – three to five inch band of wheat – that’s dead that creates a – basically after the wheat dies in a month’s time, when it’s it’s very dead, there’s just a band left behind of, of no wheat, nothing growing. So then that creates a seed bed for our beans.

1:28 So we planted the beans then on June 1st, so about a month later. We used a GPS tractor for both of those so they could be locked in exactly where we wanted to plant the beans, which was not outside the banded seed bed but actually into the seed bed. So it was a little bit of trickiness with the equipment to get that lined up just right, but using the same planter and having some high precision equipment helped out that process greatly. So we got the dry beans planted on June 1st and again, it’s been pretty hot, so those beans came up really quickly. So we had emergence on June 8th; so about a week later they started popping up through the ground and we began our sampling process around then. I should mention we also fertilized the beans right after planting. So, in any plot that had dry beans planted in it, we applied a fertilizer to help the beans out. So right at that time, we – we sampled.

2:38 So our sampling plan continues on a number of different techniques. So we took wheat head sample – or we took wheat heads, collected them in the vials and shook them in alcohol and we’ll use the alcohol extract to look for thrips, both good thrips and bad thrips, to see what – what’s – what’s going on in the wheat heads since they can be a source, particularly for thrips. And as we’ve talked about before, since thrips can both be a pest for dry beans or beneficial, it’s important to account for those. We also, in all of the plots in each treatment, we set up pitfalls – pitfall traps. So basically holes with a cylinder in the ground and a cup that we use to collect ground roaming, ground beetles, or rove beetles, or other beneficial insects that are commonly found at the soil level that are collected in pitfall samples. And then we also took vacuum samples; so if you can imagine a leaf blower on reverse, that’s basically how we took the – we take vacuum samples. So we basically put a nylon stocking on the end of a leaf blower and uh – put it on the suck end of the uh – the sucky end (very technical term there) of a leaf blower, the intake of a leaf blower and then use that for a controlled period of time to take a standard sample. And we pulled those vacuum samples out of bean rows and the wheat rows – obviously if it was wheat only, there were no beans to sample, if it was beans only, there was no wheat to sample. But even in the relay plots where we obviously have both beans growing now and wheat, we made a concerted effort to just try to sample just the bean rows and just the wheat in those, to see if there might happen to be a difference between what we are vacuum sampling within the bean rows themselves and the wheat even within that in that relay treatment overall. And then of course, we’ll compare those samples across the different treatments to see what we’ve got. Other sampling techniques that are going on right now are sticky card sampling – so we have little three by five yellow sticky cards that have a tangle trap on both sides that we suspend in the canopy, which is pretty low to the ground right now, so we keep little – kind of wide – mesh cages around the sticky cards to keep debris from blowing into the sticky cards, leaves and residue that might be on the ground since the canopy’s so low, particularly right now. That’s our approach to keeping large debris out. But then those yellow sticky cards, the yellow color is really attractive to aphids and thrips, as well as some beneficial insects like minute pirate bugs and such. So we use those yellow  cards as again yet another sampling technique. Many times when we’re sampling, we’re capturing the same insect with different techniques, but sometimes there are insects that are very specific to certain types of sampling techniques that you may or may not be aware of. So it’s good to use different tools – different sampling tools and strategies to just see if one of them works better than another to try to capture as much of the community as you can.

6:02 So basically right now, the past week, we’ve had um more than a couple days that have been in the high 90s to over 100 degrees with – um except for last night we had some cool weather and some rain that came through and that was that was pretty pleasant. But over the past week, we had some pretty high temperatures, very unusually high temperatures for June which isn’t unlike what a lot of the Midwest has experienced over this past month really is unusually high temperatures. So as a result, the wheat is finishing very aggressively, maturing along, and the beans are growing pretty aggressively as well. And also over the past month, we established soil sample soil sensors to establish soil moisture levels so we can try to keep on top of irrigation scheduling and so far that seems to be working, even though we don’t have really highly accurate soil sensors. They work well enough to just keep us out of the red. Last year we had some challenges, particularly in the relay plots not keeping up on enough soil moisture and so the beans would occasionally wilt. And you don’t want to get a crop to the point of wilting because that – sometimes you can wilt a little too much, and you actually lose plants as a result. So pleasantly, this June we’ve not seen any competition uh visually between the beans and the wheat. The wheat haven’t – the bean plants haven’t wilted due to the wheat competition.

7:42 E: Thanks so much for that update, it sounds like things are going really well out there. And Nevin, how has the first part of dry edible bean growing season gone?

Nevin: Well, dry beans are a pretty late planted crop in um well, everywhere, but the panhandle included. And the dry beans were planted last week in May, which is pretty typical. They’re usually planted towards the end of May, first part of – part of June and we we got all those in the ground by the – I think before June this year, which is pretty good for us. And there’s not actually too much going on at the moment as far as evaluating weed control. We have our pre-emergent herbicides we put on at the time of planting, or slightly before planting, or slightly after planting, and those usually give us between four to six weeks weeks of control and they’re still providing control now. Then, the date that we’re recording this is June 25th, so we’re still looking pretty good as far as weed control goes. So we haven’t done a whole lot as far as assessment and we’re not really seeing a lot of weed problems yet because those pre-emergent herbicides are still holding on.

8:52 E: Are there any specific tasks that you’ve been doing?

N: With the palmer density study, we have the palmer amaranth up and uh what we do is we went in  – when I say “we”, it’s the royal “we”. It’s actually my graduate student Joshua Miranda. But he went into the study and what we have is we have six different levels of palmer density and we just kind of wait for that palmer amaranth to naturally come up and they came up right after dry bean planting this year. There’s no herbicides applied in that trial, and then we took different colored zip ties for each different population level – so we’d have yellow for a certain population, level in red, or you know so forth – and put zip ties around all these little tiny palmer amaranth plants and they’re going to stay there all year and then Joshua goes in two to three times a week and hoes out every single other plant that emerges. So it’s a pretty time intensive trial and we have to wait until those, those palmer plants emerge before we can do anything. But luckily, they came up early so we already have the populations established in the palmer interference study. We’re just going to keep hand weeding it all summer long and that’s really all we have left to do with that one until harvest time.

10:00 E: Have you had any abnormal challenges that you’ve had to deal with this last month?

N: The only challenge we’ve had, we have one study looking at different populations and row spacings of dry edible beans. So we have – it’s a very large trial; four populations dry edible beans and four populations – uh four row spacings and all those different combinations and that study was last we had planted. It was about a week later than the others and right as the beans were emerging, we got I think three – about a third of a – third of an inch – which isn’t too much, but that came down in about less than 10 minutes and so that that really washed out a lot of soil and we’re still the process of assessing the stand from that study, but it looks like certain parts of certain plots may have experienced some stand wash.

10:53 E: I know Jeff previously mentioned that he’d been facing some challenges with the heat. Have you been seeing the same problems in your crops?

N: The beans do fine with the heat. the beans are very – as long as they have enough irrigation water, they tend to do very well with warm temperatures and that actually helps speed things along for us so uh weed development crop development um how fast we sort of get through the season a lot of times depends on how warm it is and so when we have plenty of irrigation water available and this, this year, it’s been a good year for that. And we have a lot of heat units, the season just kind of comes along a lot faster so this has been a pretty fast season because we’ve had some pretty warm temperatures in early June but nothing that’s got in the way of doing research yet.

E: Well, I hope everything comes up just fine and things keep going the way they need to be going.

11:43 How about you, Bob, what’s been happening for you the first part of the season?

Bob: Okay well, the project began uh in the latter part of April, where we put down the pre-emergence herbicide and then it was planted on the third of May and then it emerged roughly two weeks after that. Then just last week, the post-emergence herbicide was then incorporated and then we’ve again continued to irrigate every week at least once a week and then put down about a half an inch each time. The next step with this is we will be inoculating the plots in about two weeks. We got this inoculum last year from infected plants just all over, dried them and then we’ll crush them up, mix them with talcum powder and then just sprinkle that onto the heads or on into the foliage of these plants. And then we will begin hopefully to use the forecasting tools that we’ve had to begin the study to begin the monitoring or accessing the information that we need for for both the presence of the pathogen and the environment, which is what we’ll be predicting.

13:00 E: Have the abnormal June temperatures been a problem for you?

B: It – well, it hasn’t really affected it to to date. I mean we were able to get up a nice stand at this point, uh because it was also the post-emergence about a week after that, it was cultivated. So that has taken away a lot of the weeds and I
imagine we’ll – we’ll have – we’ll end up putting another application of uh herbicide down sometime in August, I’m guessing. But, but the, this – the heat lately has not really affected I don’t think the the sugar beets because this is a last, uh an older, a disease that occurs at the end of the season. So we’re not really concerned about it right now.

13:42 E: Okay. What are you doing in the upcoming months?

B: Hopefully, we’re just going to inoculate and and hope that will enhance the chance for disease to occur. And then we’ll keep irrigating, keep trying to keep it wet and and see if that won’t uh establish disease a lot quicker.

E: Great! I hope that goes smoothly for you.

14:04 Thanks everyone. Today we checked in with Jeff, Nevin, and Bob to see how they were doing in their research projects. All three of them have their crops in the ground, we’re waiting for things to come up, and we’re kind of in a holding pattern. We’ve experienced an abnormally warm June and so things are happening faster than we expect them to and for us right now, that’s alright. Tune in next time to find out more specifics about the research projects. Be sure to like this video, subscribe to our channel, and leave a comment down below. Visit our website at farmsci-ed.com for transcripts and for other episodes you may have missed.

See you next time, have a good one.

Integrated Pest Management, Weed Science

Episode 3: Introduction to Palmer Amaranth Study

Join Emily discussing with Dr. Nevin Lawrence his work on palmer amaranth in dry edible beans.

This transcript has been edited slightly for clarity and grammar.

00:18 Emily: Hi everyone! Welcome to Farm Sci-Ed. My name is Emily Stine and today we’ll be talking to Dr. Nevin Lawrence, weed scientist at the Panhandle Research and Extension Center about his project working on palmer amaranth – a weed – and dry edible beans. So sit back, relax, and let’s go talk to Nevin.

00:35 Nevin: Hi, I’m Nevin Lawrence, weed scientist at the University of Nebraska Panhandle Research and Extension Center in Scottsbluff, Nebraska and I’m a weed scientist that works on many of the specialty crops and minor crops grown in Nebraska: dry edible beans, sunflowers, potatoes, alfalfa, sugar beets.

One of the major problems that we’re seeing now in the panhandle of Nebraska is palmer amaranth. And especially in dry edible beans, this is becoming a major issue for for farmers. Palmer amaranth is a troublesome weed across much of the United States. It’s in the news quite a bit; if you’re any way involved in production agriculture,
it’s something you’re probably aware of. But for Scottsbluff, Nebraska – for western Nebraska – it’s a fairly recent weed. When I first began my position here in 2016, not a lot of the farmers actually had heard of it, nor were they dealing with it. But just a few years later, it had expanded past Nebraska into Wyoming and it’s it’s now a growing issue in our area.

1:52 Palmer amaranth is a pigweed. It’s very similar to red root pigweed, which is the more common traditional weed out in the area, but there’s some key differences. One of them is palmer amaranth has a wider germination window than red root pigweed or the other pigweeds. So it emerges earlier in the season and it could be a problem throughout the production season. Along with that earlier emergence, it’s also more competitive: it grows faster, it grows larger, it tends to have more of an impact on on crop yield. Additionally, it produces far greater number of seeds than other pigweed species. In our research we’ve done, we’ve seen up to two-, three-hundred thousand seeds produced per plant. As you get more plants that number goes down, but a pretty consistent number we’re seeing is a hundred thousand seeds per square yard or square meter. It’s a pretty consistent number amount of weed seeds that can be produced from from palmer amaranth.

But kind of more of the issue why this is a problem, is there’s just not a lot of options to control palmer amaranth and that’s because our farmers rely quite a bit on herbicide options to control it. And palmer amaranth compared to other pigweed species, such as red root pigweed, prostrate pigweed, tumble pigweed, tends to have far more cases of herbicide resistance – similar to a water hemp – but both those species can have quite a number of herbicide resistance cases. And in the minor and specialty crops within the panhandle of Nebraska, sugar beets, dry edible beans, alfalfa, sunflower, we don’t really have that many herbicide options to begin with. So when resistance does show up in in the case of dry edible beans – this is why we’re mostly concerned with ALS resistance or group two resistance – when that resistance shows up within palmer amaranth, we run out of options very fast.

Not only do we we have issues with running out of herbicide options within the minor and specialty crops, but when we do rotate to a major crop like corn, for instance, many of the options that are available throughout the rest of the country aren’t really available in our area. And the reason for that, is rotation restrictions. Our soils are low in organic matter, very sandy, high pH, and a lot of herbicides tend to stick around longer than they would in other regions additionally because those herbicides are sticking around and we’re rotating these specialty crops. Some of our crops, such as dry beans and sugar beets are very sensitive to herbicides that can be used in corn and soybeans and so we can’t use those in our rotation. So we have just less options in general than a lot of the country and we end up having not many options to control palmer amaranth, both in in the dry beans and other minor and specialty crops but also in in the corn.

4:17 So I’ve been working on palmer amaranth as my major – one of my major focuses of my position since I since I’ve been here in the Scottsbluff or the Panhandle Research and Extension Center, I’ve done work in almost all the all the crops that we grow in the region. But in the past, in dry beans in particular, we’ve we’ve looked at some of the traditional herbicide options. So a traditional program here for weed control in the panhandle of Nebraska would be either using a pre-emergent herbicide – something like Prowl and Outlook – applied at planting or after planting, or you could use a PPI herbicide where you’re going to be applying something like Eptam and Sonolan in the soil, you’re going to be tilling that in to incorporate that before planting. And then both those programs if they need to, they’re going to follow it up with a post-emergence of something like Raptor and Basagram. Raptor is a group 2 herbicide, ALS inhibiting herbicide and Basagram doesn’t really work well on palmer amaranth to begin with.

And so, those post options just don’t really work in our research. In previous work, we’ve compared basically what’s better between those pre- and those PPI options and we found pretty consistently that the PPI herbicides – likely due to the the tillage that involved with the incorporation of those herbicides – can get quite a bit more control throughout the season. Sometimes it’s enough control that you don’t even need to apply that post-emergent herbicide and so those are some just kind of basic studies we’ve done. We’ve also looked at a micro-rate program that was developed by the North Dakota State University, where several different post options were applied at reduced rates at multiple intervals throughout the season and see if that compared, well to the conventional options. Now that program contains a herbicide called Reflex. Reflex is a great option for palmer amaranth and we we found that using the micro rate program, we’re reducing rates, making multiple applications, just really didn’t see any benefits compared to just a full labeled rate of the Reflex. Unfortunately, after that trial was completed and we got the results, the Reflex label was not renewed for our area due to herbicide carryover concerns to corn, and it’s not really an option anymore. So at the moment in the Panhandle of Nebraska, we don’t have any post-emergent herbicide options to control palmer amaranth. There – there are none. They don’t work well and all we have is these soil applied herbicides applied at planting generally.

6:41 And so what I’ll be talking about this season on Farm Sci-Ed is some of our ongoing research this summer, where we’re trying to control palmer amaranth with these limited options. The the first thing that we’re doing this year to kind of better understand palmer amaranth is we’re doing an interference study, where we are allowing different densities of palmer amaranth to grow with dry edible beans all season long and the idea for that is to provide farmers a great visual tool to know what the yield impacts are if if they have some palmer amaranth escape. And so we can say, “if the density is x number plants per per yard of row or per foot of row, this is the corresponding yield reduction that you can expect” and that helps us justify further grant opportunities for future research. But it also provides farmers an idea of what the the palmer amaranth induced yield loss would be and also what the seed production could possibly be in contributing to that soil seed bank the next year. That’s the first study we’ll be talking about. The second one this year, is the evaluation of split applications of Outlook. So Outlook is labeled for both a pre-application – so planted at or before the dry beans come up – and also as a post application. Outlook will not control palmer amaranth that’s already emerged, but it will prevent palmer amaranth from emerging. So what we can do is apply Outlook at planting, and then do a second application a few weeks later and try to get some residual coverage of palmer amaranth for several weeks. And so we may be able to expand a pre-emergent application which might provide control for – let’s say four to five weeks, maybe even six weeks and really extend that to six to eight to nine to ten weeks depending if all the conditions work out and that’s really our best option right now moving forward.

Additionally, there are other dry edible bean herbicides that are similar to Outlook: Dual II Magnum or Dual Magnum is one of them (Esmacholiclor) and that product is labeled pre-, but it doesn’t have that post emergence option labeled currently. So we’re evaluating that right now to see maybe is that something that could have a label expansion and be used similar to Outlook. And so we’re evaluating multiple group 15 herbicides – also Warrant and Zidua – to see if they could have potential usage in dry edible beans to expand our options for palmer control. Another study we’re doing this year is we’re just going to be screening a whole bunch of soybean herbicides to see which ones may or may not have tolerance to dry edible beans for palmer amaranth control, because there tends to be better options in soybeans than there are in dry edible beans. There may be some overlap, and there may not. We’re also doing quite a bit of research on cover crops and so we have both a trial looking at winter planted cover crops, which is not often an option in our area because by the time corn is harvested, we don’t have time to get the winter crop in. But it’s it’s worked in other areas, so we’re evaluating that. And then we’re also looking at a spring planted cover crop which is not a very common strategy in a lot of the country but there’s potential that we can get a cover crop planted in about March area and there might be enough time before dry edible bean planting to get suppression of palmer amaranth. And so we’re looking at those programs, and seeing how we can incorporate the cover crop with herbicide programs to have a nice broad slate of options for control palmer amaranth. And then finally we’re also looking at what options in corn work best for control palmer amaranth and bring more modes of action, more herbicide diversity into the program and still allow rotation that next year in the dry edible beans and that’s more of not necessarily a research project – we’re not going to be discovering anything new – but it’s an extension project that hopefully will provide farmers with some options where they can see what works, compare prices, compare how it looks in different field trials, and make an informed decision.

10:23 Emily: Well folks, there you have it. Today we talked to Dr. Nevin Lawrence about his palmer amaranth and dry edible bean studies and discussed the different studies he’s doing – specifically looking at how weed density influences plant growth and different herbicide options for weed management and dry edible beans. Don’t forget to like this video, and subscribe to our channel for more science and education behind farming. And leave a comment if there’s something you found interesting in this video! Be sure to visit us at our website at FarmSci-Ed.com, for more information and for transcripts of this video. Have a good one!

Entomology, Integrated Pest Management, Plant Pathology, Weed Science

Episode 0: Welcome to Farm Sci-Ed!

Episode 0: Welcome to Farm Sci-Ed!


[00:19] Welcome to Farm Sci-Ed, the show where we go into the science and education behind farming. Farm Sci-Ed is a behind-the-scenes look at integrated pest management research in the western panhandle of Nebraska.

[00:29] Over the course of the season we’ll explore studies focused on some of the common agricultural pests in our region. This season we have three research projects: a wheat and dry edible bean relay study looking at conservation ecology and biological control (entomology), a series of dry edible bean and palmer amaranth studies looking at plant interference and herbicide options (weed science), and the detection and refinement of a warning system for the sugar beet pathogen Cercospora (plant pathology).

[00:59] Come join us as we explore the research Jeff, Nevin, and Bob are doing in the panhandle of Nebraska and explore the significance of their studies.

[01:01] Subscribe, follow us on social media, and visit our website at farmsci-ed.com for more science and education behind farming.