Category: 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!

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!

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!

Join Emily as she discusses the concept of a relay cropping system with Dr. Jeff Bradshaw.

00:20 Emily: Hi everyone, welcome to Farm Sci-ed; the show where we go into the science and education behind farming.
I’m Emily Stine and today I’ll be talking to Dr. Jeff Bradshaw, entomologist at the Panhandle Research and Extension Center. We’ll be discussing his research on the relay system that he’s been working on with wheat and dry edible beans. So sit back, relax, and let’s go check out what he’s been up to.

00:42 So Jeff, can you explain to me what a relay cropping system is?

Jeff: So a relay cropping system is a method of intercropping, where you have one crop that’s planted into an existing crop and particularly in our case we’re looking at a cereal – a winter cereal, winter wheat – and then we plant dry beans into it – a legume – in the spring.
So the existing crop is then harvested first.

So winter wheat would be harvested before dry beans and we’ll harvest that off the top of the dry bean canopy essentially, and then we’ll come back in September and harvest those dry beans.

So typically, in these situations, we have often times – a legume is planted into into a cereal crop where you see these types of relay crop inter-cropping systems and part of that is because of their different plants. They don’t share necessarily the same diseases or pests or even weed control technologies and strategies.

01:44 E: And how does this differ from a cover crop?

J: Yeah, it does share some similarities with the cover crop. Some of the benefits of a cover crop as the name implies, is to provide cover at a time of the year where there normally wouldn’t be right. As opposed to just bare ground, bare soil that would have the potential to blow or to lose moisture and lose some of the other benefits that that a cover crop can provide including weed competition. Basically um, by having that cover present, the way that the relay cropping system is different than a cover crop is that you’re actually running that that early crop out to harvest. So that makes it different. And then in our case there’s uh timing of the crop that coincides with some kind of key pest development throughout the the season, as well as provide some benefits to the natural enemies that are in the environment. So if we, for example, have that relay cropping system established early similar to a cover crop but then as it matures, those natural enemies that are conserved in that relay cropping system can then emigrate out of the – of that cereal and into the legumes at a time, in our case, that would hopefully coincide with when when pests become more active. And so now, those predators can be available to to attack those pests – that’s the strategy anyway.

3:12 E: So when you’re growing in a relay system
what compromises do you have to make ?

J: Yeah, so there certainly are compromises as there are um in many cases in agricultural actions. So there is the possibility of reduced yield, so we’ve got – you know – competition between the two crops on any given plot of land. When we’re looking at that that relay system so they compete for really all the inputs that go to making a plant grow. So there’s competition with water, soil moisture, for example, there’s competition for nutrients, competition with light, and so all those become a factor to consider in this relay cropping system that could be trade-offs that need to be explored. And so ultimately, what we’re doing is trying to look at what would the balance of those trade-offs be? And from a whole cropping system perspective, are the trade-offs worthwhile, because they bring some other benefit down the line, meet some other goals for for the land manager and the agriculturalist or the producer.

4:19 E: Are there other benefits the wheat and dry edible bean system provide?

J: Yeah, so initially when we thought about this particular cropping system in our conditions out here in western Nebraska, initially you know, as an entomologist, I have a – I have a bug bias, sorry to say. But uh sorry not sorry. So you know, I did think about some of these relationships that have been shown in the literature between – you know – in regards to having a crop present earlier in the season. As I mentioned earlier, how they can help establish natural enemies earlier than they would otherwise be established in the field, and making them available later in the season in higher numbers where they can be more functionally relevant. But importantly, we also thought about the production system and what some – you know – our grower is mostly concerned with yield: the amount of grain that’s that’s harvested off the field, and of course the quality of that grain. And so we did, in thinking through this, think about the production aspects first.

And then it sort of dawns on you, as you think about a little more. “Like “oh that’s kind of similar to this,” “oh there may be some other side benefits to that.” So um those would include and specifically elements we think about dry bean production here in this part of the world, there’s a lot of interest in upright beans – upright dry beans. And part of that interest is because you can use a direct harvest combine, you don’t need the the additional equipment or additional passes through a field that you would need with a prostrate bean that’s grown along the ground. Or you have to cut it and windrow it and then come out and pick it up. So there’s these benefits with this direct harvest in terms of equipment: streamlining equipment, streamlining time that a grower spends in the field harvesting the grain; the trade-off historically with direct harvest is some challenges related to getting the pods high enough off the ground. Get them high enough off the ground, where the cutter bar can actually harvest a majority of the grain. So typically, we’ve seen that there’s, there can be a lot of variability depending on equipment and production practice and soil topography and and so on that can uh interact with with yield loss. But we see somewhere around 10% yield loss in direct harvest beans that are just a matter of the mechanical harvest process.

So in a dry bean plant – in the upright morphology –
we still see a lot of the dry bean pods hang below the cutter bar. You know, less than two inches above the ground and might even touch the soil surface so what happens is as the combine goes through, the cutter bar goes through, it clips all those beans that then can’t be taken up into the combine. They just fall shattered to the ground. So one of the things we thought about in this intercropping relay system was the attributes of the plant to grow a bit taller when it detects infrared light from surrounding plants or has uh light competition. So a dry bean plant will grow taller, the inner nodes would be longer, and the thought is then, those pods would actually be higher above the ground. So that’s one other aspect that we’re looking at strictly on the agronomic production side of things to see okay now we’ve got pods that are higher of above the ground, so even though if we have these trade-offs with – as I mentioned before – soil moisture, or nutrients, or light, we may see the benefit of actually recovering more more yield because we have a taller bean.

8:04 E: What does your research look like this year?

J: Yeah, so our aspect of the relay study – so we’ve got uh – we’ve got a bug side and a weed side of the study that we’re doing. And so, on the bug side of things, we’re specifically looking at the relationship between – um – well we’ve got four treatments that we’re looking at: we’ve got dry beans only, so we actually rototilled the plot and then planted beans; so really low residue, maybe a very conventional historic type of of bean planting from the
perspective of soil management, I guess
you could say of residue management. We have the cover crop approach which is – you know – winter wheat terminated around flowering.

Really, the the wheat is terminated at bean planting, so we plant the beans and we terminate the wheat crops so basically by the time the beans come up the wheat’s dying back.

So that’s our cover crop. Then we have a wheat only, so we have plots that are just left as winter wheat they won’t have any beans to try to look at the the competition – the the wheat competition side of things from just the wheat alone. And then, of course, we’ve got our relay treatment where in that case, we created very small beds for the beans to plant in – within – in rows within the wheat. And then and then planted the beans.

9:28 E: And what are you specifically focusing on within entomology and the relay cropping system?

J: Yeah. So with these four treatments we’re looking at specifically biological control and conservation biocontrol. So right now we’re – we’ve got pitfall samples, pitfall traps that we’ve got out in each of these plots for these treatments looking at ground beetles and other arthropods that would be roaming across the ground that might be influenced by these different treatments. Specifically looking at beneficial insects in this case, so there may be one management approach that seems to increase the number of functional species groups that are important for weed seed consumption, or maybe they’re important for predation of of pests later in the season, so we’re looking at those samples.

We also have sticky card samples – sticky card traps – that we have in the field to capture any winged insects, whether they be pests or beneficial and so we’re going through those counting a lot of thrips and aphids and as well as beneficial insects like big eye bugs and so on. Then we’re also doing vacuum sampling to again capture all the arthropods – pests and beneficials – that are actually within the wheat rows but then also within the bean rows even within a treatment. So in our relay treatment for example, we’re taking vacuum samples of the bean rows and then adjacent to those also. So we’re tracking that. We’re also taking sweep depth samples and we’re counting those. And when I say we, I’m – I’m using the royal we – I’m talking about my student Jeff Cluever who’s actually doing a lot of the work, as well as a whole host of interns this summer that are are doing the hard work of being out in the field in these hot hot days. But we’re also taking flower samples from the wheat and flower samples from the dry beans when they start flowering and then later this year we’ll, we’ll collect yield of course. But then we’ll also check the beans for damage from western bean cutworms specifically.

So ultimately, kind of our target scenario in this case right now, western bean cutworm is the key pest of dry beans in this region, and so that’s sort of our target pest. As to whether or not we think the system is going to work or not from a bio control standpoint, in July, we’ll have sentinel egg masses that we put out into plots to try to estimate the rate of egg consumption by predators in these systems, to see if the different treatments – whether it’s a relay or whatever – to see what the differences are between these treatments, relative to western cutworm egg mass consumption. And then we would hope that would then translate to reduced injury in the dry beans and increased yield. And so coming back to what we talked about earlier about trade-offs, so our hope would be that we’d have a taller bean so we’d lose less yield and then because of the system that we’ve established, we would have more bio control. So we should see a higher quality bean and then historically, we’ve had to rely on chemical control means uh to manage western cutworm. So it’s a high bar, but um one bar we’ve got with this in terms of a goal post is to see if we could eliminate or significantly reduce insecticide input into the system so we may be able to replace that insecticide cost effectively with wheat seed costs and that wheat seed costs – one would hope within an ideal world – pay for itself with the grain that you collect off of the wheat crop. So sort of the production side of things, that’s kind of how we’re seeing it. We see these replacements and so ultimately, I know that we are anticipating we should see less dry bean yield in the relay system unless we fine tune it further as as the seasons go on but we would hope that we again have a higher quality bean and recover more of that yield and spend less money on on insect pest control.

13:37 E: Well folks, today we’ve talked to Dr. Jeff Bradshaw about his relay cropping system research, what some of those compromises to be made are, and what his research is specifically looking at within entomology.

Come join us next time on Farm Sci-Ed as we go into the science and education behind farming.
Be sure to like this video, subscribe, and follow us on twitter or on our website at farmsci-ed.com
for more science and education behind farming. Have a good one!