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!
