Join Emily as she walks through the topics covered over the season to close out the program.
This transcript has been edited for clarity.
0:20 Emily: Hi everyone, and welcome to the final episode of Farm Sci-Ed, the show where we go into the science and education behind farming. I’m Dr. Emily Stine, and today, you heard it right, this is the last episode. Over the course of the last year, we’ve talked to three researchers at the University of Nebraska-Lincoln Panhandle Research and Extension Center in Scottsbluff, Nebraska about their projects looking at integrated pest management and crops grown out here.
We’ve talked to Dr. Jeff Bradshaw about the wheat and dry edible bean relay study looking at entomology and the impacts different cropping systems have on the biological controls within the field. We’ve talked to Dr. Nevin Lawrence about palmer amaranth and the impact it has on dry edible bean yield. And we’ve talked to Dr. Bob Harveson about cercospora and sugar beets and the impact it has on sugar beet production.
Over the course of all three of these projects, we’ve discussed integrated pest management tactics ranging from biological control in the entomology study to chemical control and mechanical control in the palmer amaranth dry edible bean studies and chemical and cultural control with cercospora in sugar beets. We checked in with each of these researchers over the course of the year, multiple times, seeing how things like elevated temperatures, strange weather patterns, and sometimes equipment failure impacted their research projects.
We wrapped this season up talking to all three of them about integrated pest management and what it means to each of their disciplines and how each of their disciplines collaborate together in integrated pest management practices. Finally we discuss whether or not integrated pest management is sustainable, which is a complicated topic to discuss and started thinking about the ways that we can make integrated pest management more likely to be used in the future.
We hope you’ve enjoyed this season, and if you’d like to see more from us in the future, well who knows? There’s the possibility we may come back another year. Until then, sit back, relax, and keep learning. Have a good one!
Join Emily as she checks in with Jeff, Nevin, and Bob to see how their seasons wrapped up and what they’re noticing from their observations.
This transcript has been edited for clarity.
0:21 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 checking in with Jeff, Nevin, and Bob at the conclusion of their seasons to see how things went and where they’re at. So sit back, relax, and let’s go find out what they’ve been up to.
0:42 So Jeff, how did harvest in the end of your season go?
Jeff: uh It was a rough season. We did finish harvest without too many hiccups, and we see the same challenges um that we’ve generally seen before with a reduction in dry bean yield in the in the wheat bean relay.
Emily: Can you make any preliminary statements about your observations this year?
Jeff: So some of the trends from this year: one of the challenges we’ve seen I should say, this year is what we’ve mentioned before. Because of the hot summer that we had, we had some challenges in using herbicide management for for weeds. This would have been a really good year to be able to cultivate the dry bean crop obviously if in the winter wheat dry bean relay cultivation isn’t an option so without that tool, became a bit more challenging this year particularly again because of the hot summer to manage weeds really well and that clearly had an impact on on dry bean yield particularly in all the crops that had in the treatment plots that had the wheat relay treatment present. General trends that we’ve seen even in years like last year that didn’t have the same herbicide management struggles that we had this year, we saw a reduction in in dry bean yields in the wheat bean relay so we continue to look to the future to find ways to modify that treatment, motivate modify that strategy for to improve being yield. That said, we have seen a trend in improved seed quality in the wheat bean relay and what I mean by that is in in the dry beans in the wheat bean relay treatment we see a reduction of western bean cutworm damage. So that adds clear value to that treatment but again we’re still suffering from this yield drag um in that in the particular arrangement that we have in our wheat bean relay.
Emily: What are your next steps going forward?
Jeff: So right now with the project we’ve got a an ocean of samples that we’re going through we’re making progress on going through this year’s sub-samples of dry beans, scoring both the pods and the beans for western bean cutworm damage again to assess that important bean quality characteristic, as well as taking yields on those plots and sub samples and 100 seed weights to evaluate that. And then we still have quite a few samples although they’re sorted, we have a lot of insect samples from our various sampling techniques from sticky cards to pitfall traps to sweep samples and vacuum samples. They’re all sorted but we’re working on identifying individual species and doing counts again to ultimately come back to say whether or not these different treatments varied in the number of pests or the number of beneficial insects that are present. So we anticipate being through those samples probably around toward the end of February, the beginning of March uh before we have all of those data from from this field season uh fully uh fully sorted through and calculated and analyzed.
4:09 Emily: And Nevin, how is the end of your season progressing?
Nevin: uh Well the season’s still ending, we’ve got most of our crops harvested. So our potatoes, dry beans, soybeans, sugar beets, sunflowers, alfalfa, even corn, corn still to go uh but for for dry edible beans, which we’re talking about today, uh that that was harvested uh about a month ago – no um maybe a little less than that. And so we have to pull those crops off the ground and then we usually dry for a couple days or until the moisture gets ready to thresh and then we we use a combine but rather than actually combine in the field we just kind of have it running on on a cement pad and we throw a bunch of beans in there at a time from each plot and use it more of a stationary thresher. But it, that’s gone well we just have our corn to do and that’s not too big of a rush because it’s a crop that has a little bit of wiggle room for when you can when you harvest it.
Emily: Are you analyzing any data yet?
Nevin: Yeah, we’ve got most of our data analyzed. uh Well I should say the royal “we” has most data analyzed. So uh a number of the projects that we have in dry edible beans beans I still need to go through there kind of with the the fine-tooth comb we call statistics, uh but for the the ones the projects I’ve been talking about most this year has been graduate work from Joshua Miranda and he needs to graduate this semester, so he’s already got everything analyzed. So that’s been good with with several of those studies, so we have the results ready to go and that’s good to go.
Emily: Can you share some of those results with us?
Nevin: They’re not even preliminary, yeah we’re we’re starting to prepare them actually for publication right now. uh so um But they’re they’re looking good yeah uh this
dry edible bean palmer amaranth interference work kind of – as we expected – the more palmer you have, the more the dry edible bean yield goes down. We’ve found that dry edible beans are more susceptible to palmer interference than most other crops, so this sort of palmer interference work is a pretty standard type of research that occurs and it’s it’s happened in a number of different types of crops: corn, soybeans, cotton, sweet potatoes, you know you name it it’s been done already. It hasn’t been done in dry beans and dry beans appear to be more susceptible than other crops are to the palmer interference and so that’s been that’s been nice to have that in there that kind of gives farmers sort of a metric for what they can expect if they if they aren’t able to control palmer amaranth what their yield impacts can be and just to kind of put that in perspective I think we’ve seen four plants in about a thousand square yards, which is kind of a weird way of of describing that, but that that’s enough to cause a noticeable yield impact on your dry edible bean production. So not a lot of palmer to reduce dry bean yield and those plants you know each one at that low of density, each each palmer plant is going to be producing – if they’re a female, so about half of those would be female so you’re looking at about 300,000 seeds per female at that at that level of density.
So that that works been done um the other work that that we have analyzed that Josh was working on is is looking at using Outlook which is currently the only chloroacetamide or group 15 herbicide labeled in dry beans for post-emergent application. He’s been looking at using that in a sequential pre-post program where you apply it pre-emergent with Prowl usually and then before the herbicide wears off, you try to put out a second application to extend that uh period of weed suppression from from the soil soil active herbicide and we’ve been looking at two different timings sort of: a really early application, and then one that’s more in tune when growers will generally put out their post emergence herbicide and one out of three years, the data we needed to have that earlier application but the the other two years uh the timing wasn’t a factor. And what we found is having that Outlook put out as a post and even the only post herbicide or as a lay by in this case we’re getting equivalent we uh palmer amaranth control as if we were to use the herbicide Reflex or fomosaphen which is labeled in our area it’s great on palmer it’s the best palmer herbicide we have in dry beans but because of rotation restrictions, most growers in our area cannot use it so the um use of outlook seem to be equivalent and that’s good news. That’s going to be the best recommendation moving forward for growers is if they’re concerned about palmer is to use Outlook in their their post-emergent herbicide techniques.
um The third study that Joshua finished up is although Outlook is the only group 15 herbicide, the very long chain fatty acid inhibiting herbicides labeled for post-emergent application in dry edible beans, that that may change in the future so Dual Magnum is another one that Syngenta may be expanding the label on to allow applications and another one that BASF is looking into is uh Zidua or peroxisulfone and so in addition to looking at Outlook we also screened both of those herbicides to see if they provided as good control of Outlook or even better or worse, and then we threw in Warrant as well which is probably not going to be labeled in dry edible beans but we wanted to see uh if it could be and what we found is Zidua, Dual Magnum, all provided equivalent control of palmer amaranth as a in a sequential pre-post system as Outlook and that was as good as using a Reflex post-emergence. the the Warrant or acetylchloride was a bit worse but that probably wouldn’t be the best fit for the system anyways. And for both the Outlook and Dual Magnum, you could use those um uh pre-emergent and post emergent uh if the future label allows that in Dual where you could have uh use the same herbicide for both applications while the peroxisophone residual, that’s likely going to be a post only option. It’s not going to have a pre-emergent label because we did see some injury when applied pre, but you could easily just throw that in after Outlook or Dual.
Bob: Overall I guess it it we haven’t got the results back from the sugar beets
you know the tonnage in in pounds per sugar and all pounds of sugar per acre that sort of thing yet.
But overall it was very hot and very dry and so we had trouble kind of keeping them keeping them wet. I think the yields are still going to be very good, we haven’t seen that yet but at the same time, there just was not any or very much cercospora. We did see it some in the plots, but based on our different methods of like the alert system, the spornado thing, we just didn’t see any need to make any applications. We went ahead and did just so we could say we did something about it but we never in our plots never did see the values that are required for making applications. Emily: Did you hear much about cercospora being an issue this season?
Bob: I did not, no. I mean I didn’t – nobody contacted us about it, and I didn’t hear through the grapevine. I’m sure it was there in some you know localized spots but it just it it just was not as problematic this year as it often is and I think that is just due to the to the heat. A lot of it is is due to uh requirements for it is at night, say from midnight to seven and I could, you know tell you that it was still up in the 80s in in our house uh you know at midnight and so that is part of the reason why it just wasn’t as problematic problem – is that you know we weren’t able to evaluate the different treatments that we were trying to use and then so there’s that’s kind of a wash this year in terms of that.
Emily: So do you plan on repeating this study again next year?
Bob: I will plan on it, but it also will depend on Western Sugar and their desire to do it. But I am going to propose to try to do something at least something similar to this again using the alert system and using that spornado sport catching device. I want it to go well for the growers but we still need to try to do a little bit better job maybe of producing disease in our plots so we can evaluate the treatments properly.
13:17 Emily: Well folks, there you have it. With all three research projects wrapped up for the year, the researchers are on to their data crunching. We got to see some of the preliminary thoughts that they’re having but for the most part it’s wait and see until after all the data comes in. Be sure to like this video and subscribe to our channel for more episodes. Find us on twitter @TheFarmSciEd and visit our website at farmsci-ed.com for transcripts and more information. Have a good one!
Jeff, Nevin, and Bob continue their conversation about Integrated Pest Management and whether or not it is sustainable long-term.
This transcript has been edited for clarity.
0:20 Emily: Hi everyone, and welcome back to Farm Sci-Ed,
the show where we go into the science and education behind farming. I’m Emily Stine, and today we’re continuing our discussion about integrated pest management within entomology, weed science, and plant pathology. And today Jeff, Nevin, and Bob are answering the question of “Is IPM sustainable?”
Jeff: I have a short answer, and the answer is yes.
Bob: I think it has to or agriculture will not be.
0:50 Nevin: I think the first thing you do is define sustainability and there’s a lot of ways uh you know, you look at economically. Does it uh is it going to keep making money for the farmer? Does it work you know biologically? And then also does it have any negative impacts that over the long term are going to cause problems environmentally or socially? and and so basically will this practice – can we continue using it um in the future indefinitely? um and I think that’s uh that’s the question and so I’ll let I’ll let everyone answer whether or not IPM is is something that we can keep on doing.
Jeff: um well you know, there’s maybe uh gradations of that depending on the pest species that you’re looking at, and how and the system that you’re working in, so um you know from its beginning from its origin at least for uh insect integrated pest management you know, the focus has always been on um a lot of the origin was based on biological control and trying to integrate biological control and other control tools, tactics, and strategies and then incorporating economics into that. So you know for certain pests you can you can design management systems that you you might use things like conservation bio control or different strategies you might use in the field that result in possibly more land conservation, less fuel use, reduction in pesticide or herbicide in the case of weeds, that would achieve some of those what might be considered environmental sustainable goals. But then also simultaneously achieve you know reduction in input is a reduction in cost um which makes it more sustainable from an economic standpoint. That’s not possible for every pest and every weed and every pathogen. um
2:50 So the question is “is IPM sustainable?” It can be, um when optimized, when everything can be optimized and you know also kind of pulling back some of the previous episode comments i had about you know once we do the science, you get the foundations of a pest species, ecologically, biologically, you’ve got a suite of tools that you can have diverse modes of actions or compile that or add that to different strategies at the same time so integrating all those together.
Bob: Growers do that anyway.
Jeff: so you can do all the research and then ultimately the end of the day, is if the tool, the scouting tool, or uh method of sampling or determining whether or not you have a problem, if it isn’t convenient it’s not going to be adopted. It’s not going to be used
Bob: but every year they decide what which field they’re going to use for this, or the which variety they’re going to use. To me that’s – they are doing integrated pest management that way because of what it works. yes right so yes I think it’s sustainable and will continue to be.
4:02 Nevin: Depending on how you define uh IPM for weeds or integrated weed management, um the answer is no. um But it depends and the reason I talked about this in the weed science episode is um so integrated weed management is just doing a bunch of different things to control weeds and classically the definition is to reduce herbicide use. But what that’s led to is basically you do a bunch of stuff and then you rely on only a single herbicide or maybe two herbicides and that actually uh narrows the selection pressure for resistance to develop to those uh those those herbicides within the weed populations. And you you end up losing those herbicides and so uh if the goal of IPM is to reduce herbicide usage, I almost would say it’s not sustainable. uh The the related concept, which is depending on how you define it, the same thing is something called herbicide resistance management where you do a lot of practices including non-herbicide practices with the goal of not reducing herbicide use, but broadening that selection pressure to reduce the likelihood of future events of herbicide resistance from developing. So it depends what’s your goal – as a goal to not use herbicides or reduce number of herbicides then that might not be sustainable. But if your goal is to just have all the tools still be available in 20 years, then it it it likely is um as because it’s it’s a it’s a it’s a methodology, it’s not a definitive “this is what you do” and so it’s hard for a methodology I guess they’re good to go out of favor but it really depends on your goal for weeds at least.
5:42 Jeff: and yeah so I think you could say in some aspects, both for – well I think in all of our disciplines – when it comes to resistance management it’s a matter of conserving susceptible pest disease and weed traits.
Nevin: yes.
Bob: or the chemicals or the chemicals or whatever you’re trying to recover or keep those going too.
Nevin: And one of the – I guess other differences too, because a lot of this has to do with resistance is with um uh I know I – I can’t speak for the disciplines, but a lot of times whether or not that resistance trait is going to be a problem indefinitely has to do with fitness cost with it and at least for a lot of weed situations, there’s not a fitness cost. So if resistance develops it might be there forever within that population; it’s not going away.
Jeff: Yeah, whereas in some insect populations you know fitness – there are fitness costs related to to whether or not they can adapt to a certain um trait.
Bob: And they’re always going to be changing you know you can’t can’t mess with mother nature.
Jeff: yeah resistance happens, it’s just a matter of can you slow it down enough?
Bob: Right, right.
6:44 Nevin: In my mind, the whole idea of this this integrated management uh whether it’s for you know, reducing your pesticide use or just resistant costs, it’s basically just trying to you know from our standpoint we’re trying to figure out ways to help a farmer I guess be sustainable or manage that pest or be productive. But you know if if a farmer thinks in the concept of IPM, I think what they’re doing is they’re just thinking long term, they’re thinking more strategically, it’s not just decision to decision decision, it’s it’s trying to broaden out the the longevity of making decisions and I think that’s um probably the most beneficial thing.
Jeff: um yeah and I think you could say that really it’s more well at least in some cases depending on the commodity it’s more than the farmer that needs to have that long-term buy-in for IPM adoption or some of these practices whatever that might be to be executed in the practice you know whether it’s the the co-op, the agriculturalists, the farmer that’s growing it, um probably less of the consumer but we do make decisions. I mean farmers do have to make decisions depending on the commodity thinking about apples for and some of the diseases in apples and how the the look of an apple can determine its marketability, we’re driving – it’s driven by consumers
Nevin: or dry edible beans! uh hair uh nightshade can actually stain the beans pink and then you won’t buy them because who wants a pink great northern bean uh I’ll also say one thing problem with IPM is with each of us, is is we tend to research that in our own silos and so we’re only considering the disease of interest or the the pest of interest. And you know, with a farmer it’s much more difficult because they’re considering everything and so it, you know it’s we kind of do research in a silo and that doesn’t help farmers unless they’re literally managing a pest within a silo you know?
8:41 Jeff: Yeah, I was going to say it’s a good thing we have faculty with extension appointments.
Bob: yeah
Jeff: and it gives at least a little bit of playroom between us to share time and space together in terms of talking about different management concepts. At least when I present, I’m presenting with you guys many often
Nevin: yeah it’s one of us
Jeff: I do learn a little bit about weed science, maybe sometimes you learn a bit about entomology when we’re sharing our presentations together but there are opportunities at least uh in places like ours where we have shared workspaces, to come up with ideas maybe that are a little more integrated than than would otherwise be – break down some silos a little.
9:23 Emily: There’s a lot more discussion to be had about IPM and its sustainability. So to jump in on this conversation, subscribe to our channel, find us on twitter @TheFarmSciEd or visit our website at farmsci-ed.com for transcripts and other episodes. Have a good one!
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!
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.
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!
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!
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!
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.
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.
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.
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!
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?
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!
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.
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.
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!
