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Interview with a Plant Scientist: Ebony Murrell, Crop Protection Ecologist

What brought you to The Land Institute (TLI)?
The job description brought me here. I didn’t really start researching agroecology until I was a post doc. I’d never taken any agricultural classes, so I never heard about TLI in my courses until then. But when I saw the position, it was exactly the kind of agricultural research that interested me. I applied, and here I am.

 

How did you get into this field of work overall?
There are some people who just loved insects from the beginning, and it became their dream to be an entomologist someday; that was not me. When I was very small, insects terrified me. I started to find insects interesting in high school. My high school teacher, Donna Caplinger, had us create an insect collection, and I found that fascinating. In college, I was still interested in research and doing something with animals of some sort, but ecology really attracted me too – not just animals but how they react with their environment and each other. Most of the research internships I did as an undergraduate wound up having to do with insects in some way. They’re interesting, they’re easier to work with than larger organisms, and they’re short lived. So, there are many more involved questions that are easier to answer with insects when you’re doing research.

Once I saw the value of working with insect ecology, I was sold. Having said that, I’m not interested in just insects. My first love has been and always will be ecology – the interactions of organisms with each other. Sometimes those are plants interacting with each other, plants interacting with the environment, or fungi interacting with plants, and those in turn interacting with insects.

 

What are the main crops you have been working with?
Silphium and sorghum have the worst pest problems in the field, so when I first started working here, those are the crops I immediately started with. Brandon’s legume plants have a lot of pests in the greenhouse, so I’ve tried to help Tiffany (Durr) with greenhouse pests overall. Tiffany was using different essential oils in the greenhouse to manage insects, but she didn’t have a way to systematically test those oils. Not very many people raise alfalfa in the greenhouse, so she could read up on which essential oils might kill thrips but had no idea whether those oils would hurt alfalfa or not.

One of the things I’ve helped her with is developing bioassays. I have trained her how to set up containers with pieces of alfalfa in them, or we have larger containers that we grow red clover seedlings in, and then she can put thrips inside those containers and very systematically treat them with different essential oils and see which ones work best.  I have helped her design the bioassay protocols, but the research is all her own.

 

Is the main pest for sorghum chinch bugs, and are they a native pest or are they everywhere?
Chinch bugs are a native pest that heavily affect all kinds of sorghum in the United States. But there are many different pests that have the potential to attack perennial sorghum. Fall armyworm is native to the United States but has been introduced in Africa and is causing problems. It would certainly be in our interest to do studies on those and we will be soon – and by we, I mean Chase Stratton, our new post doc. He is going to be doing experiments with sorghum and whether you can inoculate it with mycorrhizae to increase its defenses against fall armyworm and the Southern corn rootworm.

 

Besides Eucosma, are there any other pests for silphium?
Silphium is a real challenge because it’s so different than any other crop that’s out there. If you think of something like perennial sorghum, it’s a cross between annual sorghum and Johnson grass, so it’s subject to the same pests as annual sorghum. There are a number of scientists who have studied sorghum, so they have figured out where its pests are located, what their life cycles are, and what kind of organic or conventional treatments you can use to help manage them. When I arrived here, chinch bugs were a terrible problem that we needed to address, but I’ve been able design a pest management plan for them based on what we already know for annual sorghum.

We don’t have any of that information for silphium. Silphium is a native plant that’s being fed on by native insects. Who cares if Eucosma giganteana is feeding on a silphium plant out on the prairie? That’s where it’s supposed to be. It’s only because we now want to raise silphium as a crop that we need to know about its pests. That’s one major reason why we work so intensively with silphium. It’s a buggy plant (both good and bad insects), but it has several different kinds of pests, and we know virtually nothing about any of them. They’re not the same pests that attack annual sunflowers. We must start from the ground up.

 

What is the idea of integrated pest management (IPM) versus trying to kill “all” the insect pests? Can you talk a little bit about the methods and philosophy behind IPM?
The philosophy behind IPM is that it’s management, not control. Control is what we tried to use with DDT. Blanket the landscape with some pesticide and kill it all, which can lead to devastating consequences. So many of our food webs rely on having insects, and if you kill everything, you’re killing the good insects as well as the bad. Also, if you push a pest too far, it will evolve resistance. The idea behind IPM is reducing a pest to a level such that the amount of damage that it incurs to your crop is less than what you would pay to treat it. Another important part of IPM is integration of techniques – you don’t rely on any one technique to manage insects, because if you try to rely on a single mechanism to manage your insects, they can adapt to that one thing.

Bt corn is a prime example. The Western corn rootworm is specialized to feed on corn; there are not too many other things that it will eat. Corn was developed with a Bt trait that is toxic to the Western corn rootworm, and it only took six years for it to develop resistance to that trait. That’s fast because it’s a specialist and relies on that crop. We have a similar situation here – Eucosma is a specialist pest. It only feeds on Silphium integrifolium and Silphium perfoliatum. If we were to try to eradicate Eucosma, it would be able to develop resistance because it must have that plant to survive. So, we don’t want to try to use any one technique to eliminate it, we want to use a variety, so we keep its numbers low and it’s less likely to be able to adapt resistance to one technique.

An important part of IPM too is monitoring the pests over time. That’s another reason why it’s important for the Crop Protection Ecology Lab to do a lot of the monitoring in the field. For example, we go out in the sorghum fields every week and count chinch bugs when they’re in season.

 

How do you count them?
You get down on your hands and knees and you pull the leaves out from the base of the sorghum plant where the chinch bugs like to hide. You count them one by one and then you go to the next plant. You’re not counting every plant. We pick a random point in the field, look at the leaves of five plants in a row, and count how many chinch bugs are on them. Then we walk over to another part of the field and select another random five plants and count how many are there.

 

That sounds like it could take hours and hours, and you’re just seeing how many chinch bugs are there, you’re not even treating them?
We’re not treating them; we’re just getting data. Once the chinch bugs are around, we’ll be counting them at least once a week. That takes two people at least half a day just to count the fields we have, and we have something like five fields of sorghum.

 

A big farm with a huge operation is not going to have the time and manpower to do that – is this just for research plots to develop some best practices and management to apply on a larger scale?
That’s the idea. We want to be able to apply some of these things on a larger scale. This is where a lot of ecological preventative measures can really be helpful in managing your insect population.

The life cycle of the chinch bug is that it lives in bunch grass in the ditch over the winter as an adult. Then in the spring it moves into wheat fields and feeds there. It’s got a little piercing sucking mouth part, so it drinks the plant juices. They grow in population in the wheat field, but don’t cause significant damage to the wheat. However, in the early summer when the wheat begins to die down, they need another food source, so the young of those chinch bugs will walk from wheat to sorghum.  Back in the early 1900s, farmers would burn the grass in the ditches in the winter and they would put in moats. I have a manual from the 1930s talking about fighting the chinch bugs by putting barriers of creosote all around your fields. That killed the chinch bugs, but it’s very toxic and flammable too. We obviously don’t advocate bringing back the creosote.

But what you can do is first, don’t plant your wheat fields next to your sorghum fields. That was a situation that we often had at TLI because the fields are so close together. The second thing is that you must make sure that whatever the chinch bugs walk through isn’t another kind of grass they can feed on, because otherwise, it just provides a bridge. This year, we’ve made sure to space the wheat fields away from the sorghum so that no two fields of that type are adjacent to one another. And then in between wheat and sorghum, we’ve planted a cover crop mixture of buckwheat, cow pea, and a little bit of foxtail millet. Foxtail millet is a grass but it’s much more resistant to chinch bugs. Buckwheat and cow pea are not grasses, they’re both forbs that the chinch bugs can’t feed on or get any nutritional value from. They’re also both flowering cover crops, which means that they’ll attract a lot of predators. You’re basically creating a dangerous barrier that the chinch bugs must walk through to try to get to the sorghum. So, it’s much more likely that the chinch bugs will be eaten before they every get to the sorghum.

If you use preventative measures like this, it’s one of the many ways that you can slow down and reduce the number of pests that get into your crop. It doesn’t require any kind of pesticide use at all, just a good planting plan.

 

I know you are trying to work with pollinators as well, like the beehives you have started. Is that specifically for the silphium or an overall pollinator plan?
Having good native bee populations is an ecosystem service for almost any system that has colorful flowers. Kernza, wheat, and sorghum don’t need pollinators. But our silphium and legumes absolutely do. For our perennial legumes and silphium, you can make the argument that the bees help the plants, but the plants also provide a refuge for the bees, because they’re perennial, so you don’t have to till the soil every year. There are a lot of solitary native bees that develop ground nests and live in holes in the soil. If you have a perennial grain in place, then that’s going to keep the soil from being tilled and you can raise healthier bee populations. At the same time, those same bees are pollinating your flowers and helping pollinate other food crops that we have. We really need to know who those pollinators are. We don’t know all the species that pollinate our legumes in Kansas and what pollinates our silphium. We are doing research to learn that through an NRCS grant, to assess the pollinator resources that are provided by our perennial grains.

 

Are you working with other beneficial insects like butterflies or predatory species?
We don’t really work with butterflies, although we will take note of them in our pollinator survey. We do care very much about the other insects. In that same NRCS study, even though the experiment was designed to look at pollinators specifically, we’re always collecting to see what predators show up in those same plots. Whenever we’re searching for chinch bugs, I keep a visual assessment of what the predators do in those fields too. We’re very careful that if we ever need to treat sorghum fields, we only treat the bottom six inches of the plant because that’s where the chinch bugs are. The predators are much higher up on the plant. If you do it right, you avoid the lady beetles Another major pest of sorghum is the sugarcane aphid which flies up from Texas every year. Those lady beetles keep the aphids under control. The aphids came last year, but because they came a little later in the year and thankfully, we had lots of lady beetles, we were able to keep them under control and didn’t have to treat for them.

It’s one big incredibly complex network, but again, that’s the integrated part of it; having healthy predator communities is an important part of integrated pest management.

 

Your plant defense work is much broader than just insects. On your webpage you mention that mycorrhizae can boost plants ability to release chemical defenses. Can you explain a little about that?
This is part of the work I started doing as a post doc at Penn State working with annual organic crops. Organic farmers in Pennsylvania like to keep their soil covered with something between cash crops so that it doesn’t erode. So, they plant cover crops, plants that are just meant to keep the soil in place. Depending on what species those cover crops are, they can provide other services too. Because cover crops grow and have roots like any other crop, they can affect what is happening belowground and provide a resource for beneficial soil microbes. One of those microbes is mycorrhizal fungi, a symbiotic fungus that forms association with plant roots. In theory if you plant a cover crop before your cash crop (like corn), that cover crop can serve as a resource for those mycorrhizae. Then those mycorrhizae are still in the soil, so they can form associations with the corn that’s planted afterwards. But different species of cover crops can be better or worse at providing good habitat for mycorrhizae.

We did research that showed depending on what kind of cover crop you planted before your corn, especially if you planted some kind of grass, you could actually increase the number of mycorrhizae that then colonize the corn later in the season. The more mycorrhizae the corn had, the better it was able to provide plant defenses when it was being eaten by the European corn borer caterpillar. Also, caterpillars that fed on the plants that had more mycorrhizae were smaller. So, there were carry-over effects.

I want to try a similar test with perennial systems, but in a perennial system, you’re not going to plant a cover crop, till it up, and then plant your perennial. The perennial is going to be there year after year. We must think of what kind of plant diversity we can provide in space, versus in time. One of the things we want to try to do is figure out which companion crops work well with our perennial grains, or which perennial grains can be cropped with each other in polycultures, so that the plants provide these networks of beneficial microbes and can help defend each other.

Sometimes it’s what you do see – you can plant a diverse system and see a lot of predators come in – but a lot of times it’s what you don’t see that matters too. These fungal networks underground improve the overall health of the plants.

 

What are some unique challenges of your work besides working with native plant/pest combo silphium and Eucosma?
Trying to decide when to focus more on pest management and when to focus more on ecology. I could easily spend all my time doing one or the other, but we need both. Ecology is important and I want to devote as much time to that as possible, but at the same time, I need to make sure that our crops aren’t getting eaten.

Being the first entomologist at TLI also means that I need to build a network in the entomology world almost from scratch to work on these issues, because there hasn’t been one. Thank goodness there were a couple of people who were starting to work on Eucosma when I first got here – that was helpful in jumpstarting our program. But in many cases, it’s just Edy (Chérémond) and I. Much of my time has been spent getting the word out to different departments when I go give talks at universities and letting them know these crops exist. These are entire study systems that almost no one is working on right now, but they’re important ones. And they’re very interesting from both an entomology and an ecological perspective. Once I talk about it, people are curious and want to get on board. I’ve been very fortunate in that regard. I’ve managed to build a network of people who I work with or who want to work with us very quickly, but it’s still a challenge having to start from ground zero.

Then there is the problem of scale. Tim works with microbes underground which aren’t very big, and the breeders work with plants which are quite a bit bigger but don’t move very far. I work with insects which disperse kilometers. If you plant a little 12’ X 12’ plot of Kernza and alfalfa, that is a perfect size to do analysis of yield, nitrogen, soil carbon, and soil organic matter. But that is a blip on the radar as far as your average grasshopper is concerned. And the average bee can fly over four miles to find food. Scale is a unique challenge when you are working with research plots to make sure that they are large enough that you can do the work that you need to do without interfering with the breeding goals, and it is one that the people here have been extraordinarily awesome about.

For example: Brandon (Schlautmann) planted a lot of interseeded crops last year, and he made sure to plant the plots large enough that I could do insect studies. I hadn’t even asked him to do that, but he recognized the importance of it and did it. That was wonderful that he was willing to do something like that!

 

Have you made any recent important discoveries?
One thing that we did find for pest management of Eucosma is that we were able to treat the soil with entomopathogenic nematodes, a kind of roundworm. It’s a type of nematode that burrows into a caterpillar or grub underground and releases a bacteria that basically kills that caterpillar and turns it into soup on the inside. The nematode feeds on it, continues multiplying inside it, eventually, the caterpillar (well dead), becomes this big bag of nematodes. At which point, the nematodes burst forth and go out to seek other caterpillars.

This type of nematode lives naturally in the soil, but they don’t necessarily live at the concentrations you need to provide insect control. Fortunately, you can buy them or breed them yourself in the laboratory and release high numbers into the field. We treated some of David’s (Van Tassel) silphium last year with these nematodes and found that even up to five weeks after we treated them, they reduced the amount of Eucosma in the roots by 50%. David treated two entire fields with them last year. We’ll see this year how well they worked over the course of the winter.

Another fascinating find was these “little brown moths” (for the longest time, we just called them “LBMs” for short.) It was hard for us to find a guide or taxonomic key to even figure out what this was, but now I’m fairly certain it’s a moth called Pelochrista womanana, which is related to Eucosma. Unlike Eucosma, it never lives in flower heads, only the stems and root crowns. We’ve also discovered a weevil pest. The weevil had been documented as being on silphium before, but we’ve actually found it on the stem and root crown. Now we know we have at least three major pests that are feeding on the root crown of these plants. Those were some important discoveries to have made.

 

What are a few goals you have for the next 5-10 years?
I really feel like we’re only beginning to scratch the surface of what polycultures can accomplish with these systems. I am very interested in learning how to manipulate plant communities for better protection of plants overall. My work with cover cropping has convinced me that polycultures are important, but that you don’t have to have it all in order to get most of what you’re looking for. What I mean by that is, in an ideal world, we would be able to plant 20 perennial grains and be able to harvest them in one field. But I think that we can get most of the functions that a prairie provides if we only have three or four species together, if they are the right species. And the right threes species in one place may not be the right three in another place. This is where sense of place comes into play.

What I would like to do is try to develop polycultures in a way that provides most of the services that a natural system would, but be able to plant them in such a way that farmers could harvest them with very little modification to the equipment that they already have. That’s the way that I think realistically we are going to be able to get perennial grains into farmers hands and planted in many fields as quickly and effectively as possible. That’s my 10-year goal.

Right now, I’m still learning each of these individual perennial grains and what they’re capable of, so that’s the short-term goal. But ultimately, I would like to be able to design polycultures and be able to show what it is that they can do.

Another thing that really interests me is how do we rehabilitate our soils so that we can get our systems up and going better? As we transition from annual to perennial systems, that’s reminiscent of ecological succession on a field that was plowed. Many of our agricultural soils now are highly degraded. They’re far removed from the prairie soils that once were because the underground microbial communities are so different. Also, the farmers themselves are removed in their own way. They know how to farm annual systems. Perennial systems are different. Even a few hundred years ago, we had Native Americans managing the prairie and living off it. That’s very different than today. So how do you transition from an annual system back into a perennial? That’s partly going to be an ecological process and it’s also going to be a human process. What I hope to achieve is to join with agroecologists, the people who deeply care about diversity in annual systems, and be able together to come up with a way that we can transition from annual systems that are diverse in time, to perennial systems that are diverse in space. How do we do that? I wish I had the answers right now.

 

It sounds like it would help for you to have a larger, global community (to be able to grow plants in more places and have more people to talk to for ideas), so you can have those bigger plots for your pollinators.
It’s very collaborative and I think one reason I’ve been able to gain supporters relatively quickly is that I know many people who are interested in how you make a more diverse, environmentally healthy agricultural system. Not all those people have worked on perennial grains, but they instantly see the value in them, and it joins very well with what their goals already were.

This is a discipline in which The Land Institute can really benefit from the agroecology community. There are many people in organic farming, conservation tillage farming, and no-till farming who are deeply interested in soil preservation, nitrogen fixation by legumes and provisioning by cover crops, and prevention of soil erosion by cover cropping or intercropping. These are practices that people are already very passionate about, and I think we can really tap into that and join forces with them to give them our spin on it, which is “Why don’t we make this whole system perennial? We’ll help you make the system perennial if you can help us to get that system going.” That’s the kind of partnerships that I seek and what I hope we can achieve in the future.

Check out the other interviews in the series!

Interview with a Plant Scientist: Kathryn Turner, Crop Protection Genetics

Interview with a Plant Scientist: Brandon Schlautman, Perennial Legumes

Interview with a Plant Scientist: Stan Cox, Perennial Sorghum

Interview with a Plant Scientist: David Van Tassel, Perennial Oilseeds

Interview with a Plant Scientist: Shuwen Wang, Perennial Wheat

Interview with a Plant Scientist: Lee De Haan, Kernza®

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