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, Plant Pathology

Episode 15: IPM in Plant Pathology

Join Emily as she and Bob discuss what Integrated Pest Management looks like within the context of plant pathology.

This transcript has been slightly edited for clarity.

0:19 Emily: Hi folks, and welcome back to Farm Sci-Ed,
the show where we go into the science and education behind farming. We’re continuing on our discussion about integrated pest management. We’re talking to Bob today about plant pathology, the disease triangle, and integrated pest management and how all three of those topics intersect.

0:37 So Bob, how does integrated pest management use the disease triangle to make decisions in plant pathology?

Bob: As a review, let’s go back to the disease triangle. There are three points on that, and without all three of them moving at the same time, disease will not occur. So that means that there must be a susceptible host, a conducive environment, and then the pathogen to be present all at the same time. And what – the way I look at IPM is it’s – it’s integrating more than just one particular item for for control. So it it integrates several different ones, multiple ones and then hopefully the combination of all these will be better than any single one.

Present examples of this would be genetic resistance, so this also removes or tries to remove the point with the susceptible host. Another thing that that’s done with this is that the fungicides that we use, this is trying to remove the pathogen. But there’s always a resistance problem with the pathogen developing resistance so that’s why that – you you must also integrate a number of different chemicals with different chemistries. And lastly, the thing that we also try to do is forecasting. Forecasting would predict what the time period was when the environment would be ready for the pathogen to begin. So if we know when that time is, we can predict when it is and then that way we can better monitor the presence of the pathogen. And then you put all these things together, and that’s really how we try to implement different types or to integrate different types of control measures.

2:27 E: Can you explain how IPM might be used in systems where cercospora specifically is present?

B: Okay, well, like – like we’re saying, if you’re going to control this this disease to the best of our abilities, we need to continue to use cultivars that have resistance, rotating different fungicides and then trying to predict the time period when those pathogens would be present. For example, like what we did this year with the spornado: we tried to catch spores to know if they were actually there. One last thing in terms of cultivation is if there are fields that are severely affected, then it would probably be better not to leave that residue on the surface of this – of the soil, because pathogen can overwinter to some degree. And so then, if you plant new crops the next year anywhere near this, then that could serve as a point source for infections later on with the wind blow – wind and water movement.

3:27 E: Are there other examples of cultural control that you could use within the context of IPM?

B: Well, the only thing I can really think of is is trying to – if there was a problem, get rid of that the remains of the uh of the plants because that that that will remove the pathogen from that that location. Something else that you can do late in the season, is reducing the sprinklers again if – unless they really need it. That also keeping the foliage wet, will also enhance the pathogens ability to germinate – regerminate and cause further problems.

4:01 E: So really, integrated pest management practices in plant pathology are pretty self-explanatory?

B: Sure, but it’s also very – people may be doing it without even knowing that they’re doing it.

4:13 E: Do you find that common?

B: I think so, because people know what what kind of – if they’ve had a train wreck in the past, and so they don’t use that particular variety. They try to select varieties that have resistance to whatever they might be concerned about.

4:28 E: Thanks Bob! Well folks, there you have it. Today we talked to Dr. Bob Harveson about integrated pest management and how it relates to plant pathology decisions. Join us next time as we go into a more in-depth conversation on integrated pest management with all three of our specialists, and continue our exploration into the science and education behind farming. Find us on twitter @TheFarmSciEd and visit our website at thefarmsci-ed.com for transcripts and more details. 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

Episode 13: Integrated Pest Management in Entomology

Join Emily as she talks to Jeff about how Integrated Pest Management (IPM) evolved from the entomology concept of “Insect Pest Management”, and what concepts are often used in making IPM related decisions.

This transcript has been edited for clarity.

0:19 Emily: Hi everyone and welcome back to an 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 taking a bit of a deviation from our discussions about specific research projects. Instead, over the next couple of episodes, we’ll be talking to Jeff, Nevin and Bob about integrated pest management and why it matters to their specific disciplines.

0:40 Today, we’re speaking to Jeff about the general concepts of IPM and how they apply to insect management. So Jeff, can you explain what the three pillars of pest management are?

Jeff: So pillars of pest management is a reference to Dr. Larry Pedego, who was not the founder of integrated pest management, but definitely one of the key proponents, particularly in the 70s of integrated pest management and and beyond, where he uses a bridge to illustrate the components of what make up integrated pest management. So in his model, the the pillars really represent um the different tools, tactics, and strategies that one can use to manage a pest, which are then built upon foundations of biology, ecology and really the science that feeds into those tools, tactics, and strategies.

1:42 E: And how is integrated pest management ecologically important?

J: Really, ecology is important for integrated pest management. Integrated pest management isn’t possible without a fundamental understanding of the ecology and biology of the pests on which you’re you’re targeting.

And so that forms the basis and the foundation that gives you an understanding of when I say ecology and biology I’m really referencing the seasonality of pests. So when does it occur throughout the season? How does it disperse throughout a field? What is its normal distribution or dispersal pattern in a given field? Does it migrate? Does it overwinter? What are the various life stages, and how long does it stay in a given life stage? What are the birth rates? What’s the normal mortality rate for a given insect or pest in general?

And so those different ecological aspects or really characteristics of of a population, is all information you can use to exploit with those various pillars of of pest management, so you can understand the timing better of when you know an insecticide or a cultural control tool might be used in the field that would basically take advantage of what you might see as an achilles heel so to speak for a given given a given pest species. And then in the framework of integrated pest management, how could you use more than one of those pillars how could we use more than one tool tactic or strategy in concert to develop a more robust resilient long-term pest management strategy.

3:30 E: How do economics factor into making IPM decisions?

J: Yeah, so we talked a lot about ecology and biology, but economics are the third part of that really important equation as to what makes integrated pest management a durable solution, you could say.

So in integrated pest management and particularly for for insect pests, maybe specifically in some pathogens as well, we can state that explicitly in a formula of cost divided by value times injury or damage times a constant or percent control expected from a given control tool or tactic. So that’s kind of wordy, but we have a very explicit formula that we can use that derives basically helps us understand an economic injury level. So for what unit of injury that a that an insect can cause to a plant, the relationship between that injury and the ultimate damage that’s caused to the plant through our research that we do, we can we can understand that relationship and we can extract that condense that really down into that EIL – economic injury level formula.

So that’s where economics fits into it at least from experimental standpoint, and it moves more into the practical as we then develop through research a better understanding on timing. So that we can develop thresholds that allow us to make a decision in the field with a tool or a tactic or strategy in a way that suppresses that that insect pest population before it ever reaches that economic injury level. And then that moves us into really the more operational aspect of integrated pest management, which is having an action threshold and then doing research on figuring out the most easily adoptable strategy for sampling to ultimately then make a decision that’s both convenient and easy and again durable for for that practitioner, grower, rancher, homeowner in some cases.

5:44 E: Can you explain how integrated pest management has evolved from insect pest management?

J: Yes in the late um really the late 1940s early 1950s um following World War II in the development of certain chemistries their um and before that time really their pest management generally was on a calendar basis uh maybe using something like farmer’s almanac or maybe more precise field history, but it was really more more of a calendar and experience based approach for for management. Once more tools became more convenient, tools like insecticides became more readily available, more diverse than what we had in the past, there became more issues with the pervasive use of those chemistries both from an environmental standpoint but really from an economic and ecological sustainability standpoint as well.

So some researchers in California had worked to develop this more economic based model which eventually became integrated pest management to try to incorporate economic factors into that decision making process, So it wasn’t just simply based on calendar or field history or experience but actually using insect numbers or some sort of proxy for plant injury to actually make a determination as to whether or not you need to spend money on an insecticide or whatever the tool or control strategy might be, because in some cases no treatment is the best option not only from the standpoint of maybe the insect – you know they may exist in low sub-economic numbers and may not need to be treated, but in some cases you have various conservation strategies or easements that can provide beneficial insects that you don’t want to reduce their numbers and maybe they’re substantial enough. And in some cases, we have economic thresholds that actually incorporate beneficial insects into that calculus as well, again helping growers make decisions that from an economic standpoint make the best sense.

8:02 E: Can you elaborate a bit more on what you mean when you say adoption of IPM practices?

J: When I talk about IPM adoption I’m really talking about incorporating an integrated pest management plan into one’s practice. And to do that, you need to know it well enough it needs to be convenient for your for your cropping system, for your for your program, that you’re working with and the the tools have to be have to make sense and have to be user friendly, if you will, for for the grower or or land manager.

So when I’m thinking about IPM adoption, I’m thinking about a couple things. At least is information about a given pest readily available? So is there an easy way for a grower or agriculturalist to access the information to even know what the tools are that are available for sampling a pass, to determining an action threshold, to knowing what the different tools are, whether it be pesticides or crop rotation strategies and whatnot.

And then the other part of it I think about are what are the scientific tools that are available, and are they convenient enough for our growers to use? Scientists like to science I guess, you can quote me on that. And so sometimes, our research papers aren’t very user friendly from a practitioner standpoint, and so more work needs to be done by perhaps people with Extension appointments that work with the Extension Service throughout the United States at our land grant universities like the University of Nebraska, can take that information and translate into a way that’s more user friendly for our growers.

So you might have a threshold that I don’t know might use some tools or some counting that actually takes a lot more time and money just to derive the information than to just make the treatment. um And so you know in some cases then more research actually is needed on finding more convenient tools to have maybe lower threshold numbers that you can use to infer how the population is developing or even using convenient shortcuts, tools that anyone might have on hand. Some cases I’ve seen thresholds for things like soybean aphids in the past and using like a quarter from your pocket to estimate, to give you a sampling area for the number of aphids that might be on a plant. Different kind of shortcut methodologies like that making it easier for decision makers to make a decision or shortening the amount of time it takes for decision maker to come to a decision, whether that decision is the treat or not treat or hey I need to come back in another week and sample more insects because I – there aren’t enough here to really make a concrete confident up or down decision on yet.

So yeah I think about all those things when I think about IPM adoption, but at the end of the day I’m really just thinking about how do we make the decision tools that we have available and the management tools that we have to available, After we make those decisions more convenient for people to use and sometimes it you know convenience is also a matter of crop value so whether that crop value is high or low your tolerance for spending more time scouting or using a given tool might change from year to year depending on that that market. So I think bringing all that together in in context is really what I think about about IPM adoption and then ultimately if we can have a suite, a strategy for IPM for a given pest and it’s reliably convenient to deploy for sampling has a robust solution of maybe multiple tools or tactics for management. So we’ve got different options for a manager to make a decision with then becomes part of the culture and becomes the way that you manage specific pest using various tools and tactics that you might use. And so then ultimately adoption is a matter of culture becomes part of the culture and practice of of how you deploy a pest management strategy against a given species.

12:19 E: So folks, today we started a new section of Farm Sci-Ed, where we talk about the science and education behind integrated pest management.

We started talking with Jeff about what the three pillars of pest management are and how they factor into integrated pest management. We also discussed how entomology and insect pest management gave way to the current integrated pest management practices. Join us next time as we talk to Nevin and Bob about their respective disciplines and what integrated pest management means to them. Find us on twitter @TheFarmSciEd

and on our website at farmsci-ed.com for transcripts and more details. 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!

Entomology, Integrated Pest Management

Episode 10: Insect Sampling and Collection

Jeff talks with Emily about insect sampling and collection for his entomology studies.

This transcript has been edited slightly for clarity.

0:23 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 Dr. Jeff Bradshaw about entomology sample collecting and the different processes he uses to get samples. So sit back, relax, and let’s go see what Jeff uses in the field.

0:42 So Jeff, can you explain the importance of sampling to entomological research?

Jeff: Insect sampling in general has a couple purposes, when it comes to pest management at least and some other disciplines as well, but there’s sampling for research essentially, and then there’s sampling to make a decision as in applied field crop pest management, and then sometimes you’re doing sampling for research for the purpose of making the decision. So the reason that’s important is there’s different levels of intensity of sampling that you might use, depending on if you’re a crop consultant and you’re trying to you know make efficient use of your time and not spend a bunch of time in the field sampling, you just need to make a decision at some level that you’re comfortable at versus when you’re doing sampling as a researcher – as a scientist – and you’re trying to use that data for other purposes, to learn more about the insect, when it occurs, how to control it at a high level of accuracy and precision.

So um sampling then for our study and for anything is one. There’s different tools that we use for sampling and then the purpose of the sampling. In our case, we’re collecting a number of different species and then using that sample to identify which species are present and then how many of those species are present within the sample.

2:06 E: What are the differences between sampling types?

J: Yeah so one other difference uh between sampling methods as I mentioned earlier: sampling for research or sampling for a decision. A lot of times we’re doing sampling for research, we’re using more than one tool. Basically attack a problem – if you will – from more than one angle, which is very common in science. Use more than one kind of method that you’re asking for, which you’re addressing, the same question because every sampling technique and tool has a slightly different bias, maybe towards different species or towards different catch efficiencies. Yeah, really what you want to do for research is you want to capture – kind of encapsulate all the different methods that you can, to try to see well, at the end of the day, if you have more than one sampling methodology or tool that you’re using, and they all kind of point in the same direction ultimately with their data, in terms of the conclusions that you can make, then you have a much more powerful conclusion because you have more than one method that you use to to arrive at it.

3:05 E: What do some of these methods look like?

J: Some of the methods that we’re using – specifically to our study – are vacuum sampling. So we have a leaf blower, which we put on the intake side of the leaf blower to use as a sucking tool and uh we cover the end with a mesh, and then move for a certain – well there’s different ways you can do it – you can move through a canopy for a certain period of time or certain distance or a combination thereof, so you have a standardized way of collecting with that tool. And so it sucks everything into the mesh and then you close the mesh around the around the sample and then put it into a plastic bag. So we’ve got vacuum sampler, got a sweep net that we use kind of similar type of sampling, you’re sampling the canopy of the plant just like you are with a with a vacuum sampler.

We have sticky cards that we leave out for a period of time and we’re targeting aphids or minute pirate bugs, aerial insects that are moving through the air and some of which are attracted to that yellow color color of this yellow sticky card. Then we use pitfall traps to ensnare organisms that are running across the soil. So essentially it’s a little more fancy than that, but it’s essentially a hole in the ground um and then the insects fall into the jar that’s within the hole and then we can pull the sample out of that.

And then we have pheromone traps that we use and those are much more specific. In this case, we’re using a pheromone to target the the pest of preference, in this case western cutworm and to trap them and to use that as just a general sampling tool to try to understand what their numbers are. And then a black light trap that we use again for for sampling purposes, and our purpose black light trap is really we’re trying to collect egg masses ultimately um from the western cutworms that are being attracted to that black light trap. And then other – you know – all those sampling tools are looking at ways to capture and then ultimately identify and count the specimens that are the species or organisms and numbers of organisms that are within the plot.

But we also have tools that we use to sample function, different tools that we use to sample function would be like sentinel prey. So we might use sentinel egg masses – so for example with a black light trap, we sample adults and then we go into the black light trap and we gather the females in the trap – well actually, gather all the western cutworms that are present in the black light, drop and then release them into a cage with corn or dry beans um and then give them 24 hours to lay eggs.

And we use those eggs that they lay on the dry bean leaves or on whole plants and we put those out into the field and then measure over a 24 hour period how many eggs are gone. You can put the eggs underneath the microscope and determine whether or not they’ve been sucked dry by a piercing insect or whether they’ve been chewed off by a chewing insect. And so that gives you just greater insight, not only the predation but maybe the type of predators that would be present and so that would sample the insects that are moving through the canopy of the plant.

Another layer of sampling would be to functionally sample the insects that are on soil – that we would use wax worms sometimes affectionately referred to as “truffles.” The way we lay out – basically clay um modeling clay with a pin that we attach the uh the wax worm to and then we leave it for a period of time, sometimes overnight, and then just we’ll have them in open cages and closed cages to expose them to the predation within individual plots. And then again, the the the data it will glean from that would be – you know – is the waxworm after 24 hours alive or dead? Is it still present? Has something ripped it off of the the pin and carried it off? um Has a piercing insect attacked it again? You can gain all those insights by – you know – kind of studying the specimen that you left, the sentinel prey that you left out with a microscope.

7:37 E: And what do you do with the samples after you’ve collected them?

J: All these different sampling methods whether we’re sampling for counts or sampling for function um take a lot of time. When we’re we’re sampling for individuals, like with the sticky cards or vacuum sample, you end up with a collection of individuals and so you have to go through the sample and identify the specimens that are there. Typically you’re not necessarily looking for everything that’s in the sample – sometimes you’re targeting specific groups or maybe specific orders.

And then at some point, you’re making educated estimate on which of those species might have high enough counts to give you some measurable differences when you start comparing treatments that is. If you have an extremely rare thing that only occurs in one sample, and it’s like one species of something that you’re you’ve rarely ever seen the sample, well, when you look at the data you’re going to have one and then a bunch of zeros and you can’t do anything with that comparatively. Whereas you may have a group – like when we’re sampling um for pitfall samples for example – again you have a bunch of insects in that sample, we know from prior research and prior soil sampling type work that ground beetles are typically have a lot of species or you can capture a lot of species with that method. And so that that family of beetles we might look specifically for and identify them to species, because we we think that that could tell us more, because we have more data associated with – this has more species or the species change between plots, where the numbers of individual species change between plot can then tell you something about either the habitat or the growth form of the canopy and different things different insights you can glean from that.

So when we collect them, they’re generally dead or we freeze them and make them dead. But generally we’re looking we’re looking at dead insects that we’re then counting. Sometimes on the sticky cards they might not be. The only sampling methods that we’re using where we’re actually looking at live insects are with the black-like trap sampling and again we’re we’re looking to keep them alive, so that the female moths can lay eggs and the eggs are alive. And so the sentinel eggs that we put out are living eggs, they’re not frozen so they they would be viable enough that they could even hatch within the plots and that again can give us some insight about that treatment and whether or not it had enough predators to kill enough the eggs that the larvae don’t hatch versus plots where you didn’t see that predation, now you have an infestation of western cutworm larvae that can then injure injure the plots.

10:45 E: What is the intent of all this collecting?

J: Yeah, so you know first we sort through it and there may be specific groups that we’re targeting. Within those specific groups, we might um identify them further to species uh or maybe the genus only and then from there you end up with a large database for each plot. Typically we might have three, four, maybe sometimes five sampling periods, so you could take that sample and repeat it throughout the season so you can multiply the numbers even more. And so so our data sheet would look like certain numbers, certain numbers of individuals, a certain species by date.

And so what we then hope to learn from that or things that you can learn are how treatments might impact the occurrence across the season of certain species. So in our wheat relay, or wheat only, we might anticipate the presence of cereal aphids and we might anticipate that they might start out pretty low in the season and increase as the wheat grows, we have more and more of those aphids and then once we harvest the wheat, probably won’t see that many of those aphids anymore since they’re pretty specific to grasses, in some cases fairly specific to wheat and and closer associated grasses.

So um so then that relationship we see with the with the ebb and flow across the sampling dates of the aphids, we can then look at the data set that has our predators and see if they track along that same line and whether or not there’s any relationship between that seasonal change in aphid numbers and the predators that are present in the field to see if kind of one begets the other, in a sense. We look across the season, we see an increase in pests and then the predators track in association with that increase and then we harvest the wheat. And those um across the season we can see that those aphids now are no longer present, but maybe the um predators stick around and then we can start to see if then those predator numbers that have maybe stayed in those plots after the wheat’s gone shifted over to western bean cutworm, or if that changed the nature of the predation rate of the sentinel egg masses, or if it changed the predation rate as a result of our wax worm truffles.

So once you have the data, there’s different ways of looking at it, you know. We could look at the species diversity of the predators, and see if that changed. We could look at species numbers to see if that changed by treatment. Obviously you could see if the treatments had no impact on either those whatsoever. And then we could – we’ll also look at correlative items like relationships between prey and predator and if any of those relationships changed as a result of the treatment or not.

13:58 E: What are you hoping to learn from it?

J: Yeah, so once we have that data set and we look at those relationships, we can look at higher order relationships between those ecological functions that we were trying to measure – the individuals and and species diversity we’re trying to measure – and see if there’s if they track at all with the yield that is reported out from the plots or the injury that we see on those beans. And usually there’s um obviously there’s a lot of variables in the field, a lot of other variables contribute to yield and quality other than just the things that we’re measuring. So typically what we would do is constrain the conclusion that we’re trying to make, so we don’t overblow the conclusion. We can say, well, this proportion of the population can account for 30 percent of the yield increase or accounts for 10 percent of the damage that we saw. We can say it’s related to this relationship.

14:50 E: Well folks, there you have it. Today we talked to Dr. Jeff Bradshaw about entomology sampling and what he does with the samples he collects from the field.

Join us next time as we go into more depth on our other topics in plant pathology entomology and weed science. Follow us on Twitter @TheFarmSciEd, be sure to check out our website at farmsci-ed.com for transcripts and more information about this program. 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

Episode 6: Biological Control in Relay Study

Join Emily as she talks to Dr. Jeff Bradshaw about biological control and what impacts that has in his dry edible bean and wheat relay study.

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’re talking to entomologist Dr. Jeff Bradshaw about conservation biological control and entomology, specifically in his relay plot study. So sit back, relax, and let’s go find out all about this.

So Jeff, can you explain what biological control is?

00:46 Jeff: So biological control is a part of integrated pest management. So it’s a tool – a tactic if you will – that’s used along with a number of other tactics in integrated pest management to reduce pest numbers, regulate those populations in a different way. So an alternative approach sometimes in a compatible way with other approaches, tactics, tools that might be used for for pest management .

01:13 E: What kind of strategies are typically used within biological control?

J: So generally speaking, there’s kind of three strategies to biological control. There’s classical biological control, which historically has involved and focused more on invasive species where you have a non-native insect – a pest whether it’s a pest of ornamentals or crops or other situations that a pest might arise in – that are introduced into the non-native habitat to that particular insect. And then you – the classical approach would be to go to the location where it’s native for the in the pest – in the case of the pest – you’d go to a location where the pest is native. And you would study and seek out the the natural enemies and maybe the parasitoids that might be highly specific to that species. And then there are a number of approaches then to introduce that that parasitoid, for example, into that new environment to try to see seek opportunities for control of that non-native species. So a classical approach is really focused generally on invasive species and trying to import those regulatory – regulating organisms into the environment.

Now the other approaches – augmentative biological control is where you have some understanding of what the pest’s existing natural enemy complex might be and you are releasing another natural enemy – such as a parasitoid – to augment or to increase the mortality of that pest through adding more natural enemies into the environment. And then conservation biological control is where you’re using different strategies or tactics in the environment through maybe changing the cropping system, rotation strategy, or some strategy that you might be using in the landscape – certain plantings of flowers or woody habitat maybe – that would provide habitat for natural enemies to to survive the winter or survive when the pest isn’t around. So three kind of general tactics um strategies that are considered in biological control.

03:31 E: What are the specific focuses you have within your study?

J: So currently, we’re looking at – we’re focusing on kind of two different areas of biological control. We’re looking at augmentative biological control with parasitoid wasps that attack the western bean cutworm and then we’re also looking at conservation biological control, primarily within the field, and looking at different strategies that we could use in cropping production systems that would bolster natural enemy populations; again specifically to attack western bean cutworm.

04:07 E: What are the differences between cover crop and relay biological control?

J: Relay cropping is a type of cover cropping. The main difference is termination time. So we’re looking at this study, our hypothesis is that if we have crops growing – we have something growing in the field before our main cash crop – dry beans in this case – that that

that that crop can provide habitat to natural enemies. So like I mentioned earlier, that would be a conservation biological control approach, and the main difference and the hypothesis we’re looking at is that the length of time that we have a crop in the field, in this case winter wheat, prior to our cash crop, dry beans, that length of time will influence the natural enemy population that is then available for the control of western bean cutworm. So in the case of the cover crop, we’re using a cereal winter wheat and we’re – we terminated that in late May, early June

as opposed to the release – relay system which is also using winter wheat as the cover, if you will, but instead of terminating it in June, we’re allowing that wheat to senesce naturally so that it will dry down and become ripe in around now – first week of July and so we think – there’s a possibility anyway – that that timing of when that winter crop is either terminated or senesces

naturally, will have an influence on the abundance and ecological function of those natural enemies in that system.

05:52 E: Can you share some of the arthropods that you expect to see within these systems?

J: Yeah, so the cover or relay crop in this case – uh winter wheat – is uh is a cereal and as a cereal, it can be a host to a number of aphid species like the Russian wheat aphid for example, and typically, those while – those insects can be very numerous and be economic pests in their own right in wheat. Generally that’s not often the case, at least in recent years, but they’re always present, so those aphids can serve as a food source for natural enemies so those would be lacewings,
ladybird beetles, big-eyed bugs, a number of different chewing or sucking insects that are generalist natural enemies that might attack aphids. We know they have a fairly large diverse diet and so they will also go after other pests.

So in the case of dry beans, what we’re hoping is of course, those those aphids are cereal aphids so they don’t go – dry beans aren’t a host for those aphids. So that’s a key aspect in the system that that helps make it work. Obviously, if the aphids in the wheat were pests of dry beans then we’d be setting ourselves up to a pretty bad situation. But in this case, again, the aphids aren’t compatible with the dry beans, but the natural enemies that they attract in
the wheat will feed on western bean cutworm eggs or thrips, either of which could be pests in in dry beans.

So our hope then is that we’ll have a early season establishment. Some of those aphid species for example, over-winter in wheat and so those can be available as a food source for those natural enemies as soon as they finish overwintering and start to come out in the spring. So that should give a lot of time for those natural enemies to feed, lay eggs, and build up those natural populations over time. And again, we would – our question is – that those populations might build up to larger numbers because they’ll have more time to develop in the relay system as compared to the cover crop system, at least under our conditions and the way that we’re looking at the system here.

And so timing wise, then we’re really kind of focused on the western bean cutworm – because it is a key pest of dry beans and as soon as – pretty close to when wheat senesces and typically is harvested in first or second week of June in any given year. That’s also really close to when we typically start to see one to five percent emergence of western bean cutworm and that can fluctuate given the year and the – you know the temperatures – and how they accumulate over the season. But that’s that’s kind of our goal is to try to target those natural enemies flushing off the wheat in high numbers to be present to uh – basically munch on those Western cutworm eggs that are are laid in dry beans.

09:03 E: You went into some detail on conservation biological control within your study. Can you elaborate a little bit on the augmentative biological control aspect?

J: Yeah, so the other part of our study we’ve looked at is augmentative biological control using Trichogramma ostrinae as a parasitoid of western bean cutworm eggs. And it was originally introduced into the US through a classical biological control program against the European corn borer. So that was a non-native introduced pest many years ago. And the biological control lab at Cornell University looked at this particular parasitoid wasp as a potential biological control agent.

Through the years, there had been some research, some science done looking at – um – the ability for that particular wasp to attack a couple other pest groups and we had done some early work looking at whether or not it would –
it found western bean cutworm eggs to be suitable, and we confirmed that they did at least in a laboratory. And then we did some field releases a couple years back, in – in cages to try to see if – in the field to see if there was uh any hope that there – you know if we showed it in a laboratory, but what you find in a lab doesn’t necessarily translate to what you find in the field. So we did sort of a semi-caged design in the field and kind of showed that yeah, it was still compatible host – the western bean cutworm eggs to trichogramma wasps there. So for a couple years, for three years actually, we did large-scale field releases on commercial dry bean fields and we used sentinel egg masses and sticky cards over – in every case a 10 acre square to look at the dispersal and dispersion of those wasps as well as their ability to attack western bean cutworms over that very large area.

And we’re still working on analyzing those findings, but generally we found that it seems like Trichograma ostrinae doesn’t really like Western Nebraska that much. It seems to work really well on the east coast, whether it’s green peppers or potatoes or sweet corn but for reasons we’re still sort of kind of fine-tuning what the next hypothesis might be as to why they might not work as well. But right now, we think it has to do with the environment, the climate that we live in is quite a bit different than than the east coast. If you’re not familiar with western Nebraska, it’s a semi-arid environment and semi-arid is definitely not how you defined upper New York state. So we think that probably plays a part in the success and why we had fairly low, fairly low parasitism rates.

12:12 E: Awesome, thanks Jeff. Folks, today we talked to Dr. Jeff Bradshaw about biological control and the different methods they’re using within the relay plot study. Join us next time as we go into more methods in these studies. Be sure to like this video, comment below, and subscribe to our channel for more updates. Visit our website at farmsci-ed.com for more videos and transcripts. Follow us on Twitter @theFarmSciEd for more information and for catching up on all those things you may have missed. Have a good one!