Biocontrol at Play in the Insect Playground with Dr. Sanford Eigenbrode

Podcast: Play in new window | Download

Subscribe on iTunes | Android | Stitcher | SoundCloud | Spotify | RSS feed

Episode transcription:

[MUSIC]

Drew Lyon: Hello, welcome to the WSU Wheat Beat podcast. I’m your host, Drew Lyon, and I want to thank you for joining me as we explore the world of small grains production and research at Washington State University. In each episode, I speak with researchers from WSU and the USDA-ARS to provide you with insights into the latest research on wheat and barley production.

If you enjoy the WSU Wheat Beat podcast, do us a favor and subscribe on iTunes or your favorite podcast app and leave us a review so others can find the show too.

[MUSIC]

My guest today is Dr. Sanford Eigenbrode. Sanford is a distinguished professor in the Department of Entomology, Plant Pathology, and Nematology at the University of Idaho in Moscow. He trained at Cornell and did a post-doc at UC-Riverside focused on host plant resistance in fresh market tomatoes, then did a postdoc at the University of Arizona as part of a Plant Science by Entomology NSF Interdisciplinary Program before heading up to the University of Idaho in 1995 to study the chemical ecology of insects and plant insect interactions. In more recent years, he has also become involved in integrated research, education, and outreach concerning the effects of changing climates on production systems in the northwest. Hello, Sanford.

Dr. Sanford Eigenbrode: Good morning. Hi, Drew.

Drew Lyon: So, when you did arrive at the University of Idaho back in 1995, what were the earliest issues you remember working on?

Dr. Sanford Eigenbrode: So, when I arrived, I came from that program that I mentioned—you know, or you mentioned in my bio there–and University of Arizona. I had been working even since my dissertation on the effects of variation in plant waxes on insect pests and beneficials. And I had been doing that in a number of different systems. So, when I arrived here, it was the de facto system I should work in: peas.

That was a big issue at the time and it still is an important crop here, but in those days, there was a lot of acreage of peas. And I was able to work with the folks like Chuck Simon over here at the ARS on Pisum sativum peas that varied in plant wax based on genetics. And, there are like eight genes, at the time anyway, in peas that affected the wax and I was able to get in there and start studying those variants and their effects on beneficials and pests of peas.

So, this was intended to be an opportunity to sort of bridge the basic and applied dimensions of my discipline, where I always have sought to try to make some impact. And, it was surprising and interesting that these single-gene mutations do have pretty large effects on the predators and on the pests, especially the aphids in peas. So, we worked on that, we characterized those waxes chemically and physically, scanning electron micrographs. We devised methods to measure precisely the traction that predators like ladybugs could obtain on those wax surfaces and we showed that variation, genetically based variation in that trait clearly and strongly affected ladybug ability to take out aphids. And that was verified and validated in field trials with these genetic variants. We could see whole communities shifting because of that. We could see if we caged out the predators, we could see the strong effect of these waxes on those guys.

So, I worked on that for probably several, 3 or 4 years. We got good federal funding to work on that from USDA. Then I kept on presenting this to Dry Pea and Lentil [Council] and to the pea growers, and they were interested and supportive, but they had other issues and especially, at the time and someday again, this is going to be the case, viruses affecting those crops.

So, that caused a big shift in my focus to work on that. Because the feedback from the producers was, “This is what you need to work on. This is the thing that’s really a problem for us.” And I saw opportunities to do my work there that would meld the chemical ecology dimensions of my science with something that was really affecting the industry here, so I moved into that.

Drew Lyon: I’m kind of curious about this wax affecting–you said the traction of the ladybug. So, if they could get more traction, they were better predators then if they couldn’t?

Dr. Sanford Eigenbrode: Totally.

Drew Lyon: Really? Okay.

Dr. Sanford Eigenbrode: We could get really good significant fine relationships between the traction measured in millinewtons based on this instrument we developed and how many aphids they could take out in a day, in a week, whatever. It was very nice. And different ladybugs had different traction capacities and that was correlated with their ability to remove aphids from a waxy surface, like a pea plant.

Drew Lyon: Okay. You know, as a weed scientist, the wax affects penetration of herbicides in the plant leaf, but I never thought about it from this aspect of how it affects what insects can walk and run and play predator games, so that’s very interesting.

Dr. Sanford Eigenbrode: Yeah. I had my wax literature out one time and Don Thill just pounced on it because, you know, of that—of what you say, you know. The waxes are really important–and in fact, they’re so important for the function of the plant cuticle that you start messing around with them genetically [and] there are risks associated. So, in Brassica, you reduce the waxes, you’re going to get more blackleg. So, that was a limitation which I think still can be surmounted for this kind of application.

But, [I] moved on to those viruses. I think just the concept that a breeder, a plant breeder can adjust a plant so that biocontrol works better is a really important one. But, it’s hard to do.

Drew Lyon: Yeah. I could see that becoming more important as insects develop more resistance to insecticides and people have to look at other methods to keep insects managed.

Dr. Sanford Eigenbrode: Biocontrol is in play all the time. I mean, in our peas, for example, or wheat, if you shield the system from the natural enemies, you can be sure you’ll have blow ups. They’re always working out there. We don’t necessarily always document it, but they’re important parts of our production systems. Always.

Drew Lyon: Okay. You talked about viruses. Are these insect-vectored viruses or?

Dr. Sanford Eigenbrode: That’s right.

Drew Lyon: Okay. Do waxes play a role there as well?

Dr. Sanford Eigenbrode: You know, that [is] always on my mind. Can I connect the wax part, you know, with the virus part? And I haven’t been able to connect it.

We did a couple of things. First of all, we fell upon a result from folks that were working down at Parma Experiment Station that indicated that potato leafroll virus, which is transmitted by Myzus persicae, the green peach aphid primarily, but there are others–when plants were infected with that virus, the aphids showed some different behaviors related to the infected plants. It looked like attraction. So, that seemed like an ideal playground, so to speak, for a chemical ecologist. So, we worked on that system: potato leafroll virus, potatoes, Myzus persicae, green peach aphid, that is–and we showed that it’s a pretty strong effect.

So, when potatoes are infected with potato leaf roll virus, Myzus persicae is attracted to it. They’re attracted not to the way the plants look, not to the way the plants feel or taste, but to the smell of those plants. The volatile profile from an infected plant is altered significantly by infection. In a way, the aphids respond to.

So, we did that. We ultimately saw the same thing happening in wheat, the same thing happening in peas, and we published those works and kind of delved into how that would work in all those systems. In wheat, it was barley yellow dwarf virus and R. padi [bird cherry-oat aphid], and in peas it was bean leafroll virus and pea enation mosaic virus and pea aphid. Since then, this phenomenon has been observed in hundreds of systems. …I’m satisfied because we sort of started peeling back that onion for this part of the biology.

For peas though, [we] took a different tack, which was how can we help pea producers in this region better manage those viruses which are transmitted by the pea aphid? So, we set up a monitoring system–it took a few years to figure out how to do it–that would collect aphids as they migrated into our region and test them for the viruses, because not every year was a virus year. Right? It was like every five years, six years, some intervals no virus, and then there would be an outbreak. So, producers really needed to have a handle on when are those outbreaks probable or when are they going to occur, because when the aphids arrive here and they do migrate here from the Columbia Basin and beyond, if they’re carrying virus then that’s a problem. If they’re not carrying virus, it’s less of a problem. So, we trapped aphids and we measured whether they were carrying virus using a network of traps all through the Palouse region. And we got some federal funding for that and that resulted in what we now call the aphid tracker or Legume Virus Project, which is still operating.

I have 22 years of data now on aphids coming in, testing them for virus, reporting that through a website that can be accessed by producers. They can also go in there and see all 20 years of those records. You can see the map locations of the traps. And we also developed some decision support tools based on that: what to do about the virus and what to do in terms of a direct injury level threshold for the pea aphid if there’s no virus. So, we went on to try to provide a comprehensive toolkit to address this problem and I’m pretty satisfied with that. And, it still gets use.

We had to fund it from a USDA-RAMP program first, and then some of it was funded through the REACCH project, and then some of it was funded through regional IPM grants or statewide IPM grants. Some of it was funded by the Dry Pea and Lentil Commission, some of it was funded by ProGene. So, we’ve kept it supported through different mechanisms over those 22 years and we’ll keep doing it.

The pressure from viruses has eased and I think that’s because of the widespread use of neonic seed treatments, Cruiser and Gaucho. They can inhibit the spread of virus and a lot of producers are routinely treating with those products now. And I think that’s helping.

Of course, those neonics, they may not be available forever. So, the system, I think, is waiting in the wings to be important again, if we can sustain it all the way through there. And we did field work to find out how well those neonic seed treatments at different rates and different products could limit the spread of viruses in field plots and very good data there shows that they do work for that, so I think that falls into a story.

Drew Lyon: Yeah, that’s very good. So, maintaining funding for that many years is quite a challenge anymore, so congrats on being able to do that. It obviously has some value or you wouldn’t have been able to do that for so long.

Dr. Sanford Eigenbrode: Thank you. We still could improve it, but, you know–and we have improved it over the years.

Drew Lyon: So, I wonder if you can prognosticate for us a little bit about what you see as potential insect disease issues coming in the next 5 to 10 years?

Dr. Sanford Eigenbrode: Well, of course, coming, you know, implies something here that’s not here now. And, there’s certainly evidence of that and we can expect that. Global traffic is continually moving insects around. Invasive species or new or adventive pests in our systems are inevitable. Fortunately, we’re not in Florida where they see like 15 new ones a year, you know, in their systems down there, something like that. Being in a cooler temperate zone helps.

But I have been working on a new aphid called Metopolophium festucae cerealium. That’s a mouthful, but it’s an aphid that hasn’t been detected in North America prior to our finding it in wheat. And that aphid is in many locations around the northwest, in central Washington, and northern Idaho. [It is] the second or first most abundant aphid that we find in wheat. And so, we have federal funding to work on that thing.

So, I don’t want to get into that too much. To answer your question though, I think checking, being aware that there’ll be, you know, new pests to be alert to and some of them may fit right in and be relatively easy to incorporate into our management and others might introduce new challenges.

And for climate change, which I have worked on a bit lately, that complicates our systems. You know, it has been said a few times very eloquently, you know, it just adds another layer of complexity to our pest management.

If winters are warmer, overwintering conditions for creatures like cereal leaf beetle improve and can allow, you know, stronger resurgences. It can affect the phenology of pests and natural enemies. So, that is changing and I don’t think anyone doubts that there is a trend, a warming trend in progress here in the northwest.

Now what do we do about that? I think, the way I interpret that is, you know, since so many of these effects are hard to predict because of the complexity of agroecosystems, it just means be alert, be attentive, don’t make assumptions about pest abundance and patterns of pest abundance because they’re likely to shift with climate.

On the other hand, you can try to be proactive. So, we run models to see how the flux of pea aphids might change with an anticipated warming trend into the middle of this century. And more or less, those flights don’t seem to, based on models, shift very much, so some systems seem to be more resilient or robust to climate change than other or some elements of our systems.

Drew Lyon: Okay. I kind of wanted to finish up on climate because that is an area you’ve been working on recently. What have you found most intriguing about the research in that area and how this part of the world, the Pacific Northwest, can improve its resilience to these changes?

Dr. Sanford Eigenbrode: Yeah. So, part of this story is that it’s not entomological alone. And, a trajectory of my career is to see entomology and pest management within a broader context of whole production systems, to be integrators the way farmers have to be and have always been, trying to do that together. So, the REACCH project, which some people know and the LIT project and my current project, Innovative Agriculture and Marketing Partnership for Idaho, are looking at practices that are known to impart some resilience, basically by bolstering soil health–that’s the way you do it–and also mitigate the emission of greenhouse gases from those systems into the climate system. Both things can work in concert.

So, all the good work on regenerative ag that we have going on in our region and across the country is consistent with what we should do to maintain our production systems under those changes. Keeping the soil covered, cover crops, although difficult to grow and manage here are feasible–and there are early adopters working on those things–changing our nutrient management practices, diversifying our cropping rotations. Those are all part of the suite of so-called “climate smart”–I don’t necessarily like that term–but climate-smart practices that are being incentivized here and elsewhere.

My take on that, though, is you start doing that, introduce a cover crop–you do interseeding, maybe you decide you’re going to try peaola, I don’t know. And if you do those things, the implications for pests and disease management are significant to the point where those things may be a more influential downstream effect of climate change than climate change itself, at least in the near term.

Producers change what they do. Pests change in response. So, that is going to be a requirement for diligence, I talked about before–when you introduce a cover crop, for example. What happens if you introduce a leguminous cover crop and it becomes widespread and it is a host for these viruses, and we don’t treat the cover crop seed with neonics? So, we provide suddenly, you know, we provide a new habitat, a green bridge for viruses that can subsequently affect any one of our pulse crops. That’s just an example. I don’t have data to show that, but we are looking at that as part of my new project with cover crops and vector-borne pathogens. There’s a component of the new project to check that out. So, that’s kind of the interface between my work and climate change and agricultural change.

Drew Lyon: Well, thank you, Sanford. As a weed scientist, crop rotation is an important tool for weed management as well. And we’ve also in the last few years seen more Wheat Streak Mosaic Virus in areas where people have been growing cover crops and they have a–sometimes it’s wheat, sometimes it’s some other grass crop in there–that acts as a green bridge. So, thinking about what you have in there and how it might affect, will have impacts and we’ll just have to–there’s some really interesting innovations occurring out there and we’ll just have to watch and keep vigilant and see how it not only helps soil quality but may affect these other pest issues as well.

Dr. Sanford Eigenbrode: And that’s great. That’s our job, right?

Drew Lyon: Yep.

Dr. Sanford Eigenbrode: At the land grant universities, University of Idaho, where I’m from, and WSU, for our region, we need to do as good a job as we can at listening, tracking what producers are doing, innovative producers, all the things that are going on around us. It’s tough to keep up really and provide the science that’s needed to support some of that. But that’s what we should be doing.

Drew Lyon: Exactly. Well, thank you very much for being my guest. I really appreciate having you on. You have a wealth of experience in the region and thank you for sharing that with some of our listeners today.

Dr. Sanford Eigenbrode: Thanks for the opportunity to chat with you, Drew.

Drew Lyon:

[MUSIC]

Thanks for joining us and listening to the WSU Wheat Beat podcast. If you like what you hear don’t forget to subscribe and leave a review on iTunes or your favorite podcast app. If you have questions or topics you’d like to hear on future episodes, please email me at drew.lyon — that’s lyon@wsu.edu — (drew.lyon@wsu.edu). You can find us online at smallgrains.wsu.edu and on Facebook and Twitter [X] @WSUSmallGrains. The WSU Wheat Beat podcast is a production of CAHNRS Communications and the College of Agricultural, Human, and Natural Resource Sciences at Washington State University.

I’m Drew Lyon, we’ll see you next time.

[MUSIC]

---

The views, thoughts, and opinions expressed by guests of this podcast are their own and does not imply Washington State University’s endorsement.