Built-In Pest Management

Researcher Joe Lewis and researcher/farmer Alton Walker discuss how to harness nature’s built-in mechanisms to keep pests in check in order to successfully grow healthy crops

This is a joint interview with entomologist Joe Lewis and entomologist/farmer Alton Walker. Lewis spent his career as a Ph.D. researching parasitic wasps and how to restore ecological balance in cotton fields with USDA in Georgia, and he is the author of A New Farm Language: How a Sharecropper’s Son Discovered a World of Talking Plants, Smart Insects, and Natural Solutions. Walker, who also has a Ph.D. in entomology, farmed 600 acres of cotton and other crops south of Augusta, Georgia, from the 1990s until a few years ago. Lewis and Walker went to school together at Mississippi State in the 1960s and collaborated on research for several decades. Interviewing them together provides an opportunity, we hope, to see how ecological principles are put into practice; Walker’s story of his farming career is included in the text boxes.

Acres U.S.A. For those who haven’t read your book, could you give us a brief overview of your background? 

Lewis. I come primarily from the research side. I had a full career working on beneficial insects, plant-pest relationships, and pest management. I started my career about the time Rachel Carson wrote her book, Silent Spring, which exposed the harms of the pesticide DDT. 

Going back a bit further, though, when the industrial revolution came about, humankind began to lose our appreciation of the built-in strengths of living systems. I think it’s important to step back and realize that our entire universe and all that’s associated with it is made up of systems within systems. When you’re dealing with the health of those different systems, you have to think in terms of a full system. Since the industrial revolution we’ve had a lot of inventions that were spectacular, but we’ve tended to lose our appreciation for the power within the system. 

An example of this was DDT for pest control. When it was discovered at the time of World War II, it was so spectacular as a control agent for different pests. It solved a lot of problems with mosquitoes and helped control malaria and other pests that attacked different plants. Just a small amount was miraculous. It really reduced human suffering. But we moved almost completely into the use of pesticides as the way to control pests, rather than to build up the built-in mechanisms that already existed to control them. It’s very important to know that in all these situations where you have a pest or an infection, nature does have a built-in mechanism to control it. There are beneficial insects and other built-in mechanisms within cropping systems that help prevent a pest like the cotton bollworm from being a pest. 

The same thing happened with penicillin in the field of healthcare. Penicillin and pain killers were so miraculous that we starting using these interventions to control the problem. That’s become the universal approach. I think that humankind began to think that it was easy to control any undesired variable, like infections and pain and pests, by just using something that came in a bottle. We lost our understanding built-in systems. 

Acres U.S.A. Our ecological understanding of things.

Lewis. Yes. The solution is within the system. 

Acres U.S.A. Where were you doing your research?

Lewis. I ended up in Tifton, Georgia, as a research scientist at the University of Georgia campus there, but associated with USDA, and I was working on how to improve our use of biological controls as a system for managing pests.

I was starting to understand the idea of using natural enemies to control pests, but the prevalent view at that time was that we could apply these beneficial insects like a pesticide, and that would reduce the use of toxic chemicals. But I started to realize that when you started intervening into living agricultural ecosystems by using pesticides, the problem wasn’t just that there was pesticide residue; there a lot of other problems. You disrupted the balance of the system. The beneficial insects that we produced in the lab weren’t the same. We found out that beneficial parasitic wasps, when we mass produced them in the lab and released them into the field, weren’t the same creature. The wasps in the lab, reared on an artificial diet — different from what an actual crop field — didn’t learn the same way as parasitic wasps reared in the field. We often have too much of a reductionist view. 

I was studying the use of beneficial insects like parasitic insects and other predators like the lady beetle — natural enemies of pests like the cotton bollworm. At the time we had no understanding of how spectacular these natural predators were and how they had to interact as a part of the system of that web in order to make them work. But the idea of producing thousands of them and using them like a biopesticide that wouldn’t be poisonous or toxic to the environment — that was the predominant vision of the future. That was just using the same mechanisms of intervention from outside the system. But we started to realize that we had to work together — soil scientists, plant scientists, and biological controls, all together as a whole system. We were using too much pesticide and too much fertilizer. It was an intervention treadmill. 

We have to stop looking for these spectacular interventions from outside. That really does more harm than good. The solution becomes a problem.

Acres U.S.A. How did we get to this place, where we we’ve become so reductionistic in our thinking about agriculture?

Lewis. Farming is moving, like everything, down a similar path. We’ve moved away from small family farms, where you had an ecosystem, with a mixture of cattle and small fields of different crops — where you had diversity. We didn’t have these monoculture fields with huge tractors. This reductionist approach that we have is moving further away from an ecological system, toward one where you just overpower everything. If you’re going to be a specialist in growing cotton, you grow cotton. If you’re a specialist in corn in the Midwest, you just grow acres of that. And we protect it by hammering everything else out, because we have all these miraculous pesticides. 

By the late ’80s, we realized that the boll weevil was going to be eradicated — we could see that was coming. The eradication of the boll weevil doesn’t fit some of these principles we’re talking about because it was an invasive species — it didn’t have natural enemies — and for a while it was a tremendous pest problem. But once it was gone, we realized we could basically manage the other pests by built-in mechanisms.

We realized that there were several principles we were going to have to get back to. One was that we had to perennialize the system. We needed cover crops in the system. But it wasn’t just the cover crops — originally the interest in cover crops was to prevent erosion by keeping some residue in the soil. We realized they were much more important than that, though. 

The point we were making was to practice something much more holistic — to not just think about how to solve an insect pest problem but how to farm in a sustainable system, leveraging all these attributes of interactions. We were uncovering things that showed just how powerful those built-in powers were.

Lewis. The boll weevil was the primary pest, but once you treated for weevils, you woke up those big dogs. When I was a youngster, I’d walk along this country road where I grew up, and I’d see a big old dog sitting on the doorstep who was asleep. I’d think, “I can walk by that house quietly without waking that dog up,” but while I was passing by, the neighbor’s little dog would come running out there, barking and yapping. The little dog couldn’t harm me, but he could wake up that big dog.  

And that’s the problem. Bollworm is typically not a pest, but once you had weevil in the system, you’d have to spray for it because it was an invasive species without natural enemies. Once you sprayed for the weevil, though, you triggered all these things, from aphids to spider mites — and the bollworm in particular, which was really hard to kill once you kill the natural enemies that disrupt them. 

That’s what we saw coming — the boll weevil was eradicated, and we knew we could control everything else without pesticides. But the conventional programs thought they were going to solve that problem with the use of Bt cotton. There were a few years before Bt cotton came in that we didn’t hardly need any treatments because we didn’t have the stink bug. The conventional folks gave the credit to Bt for no longer needing to spray for bollworm — but that wasn’t it. We didn’t have any problem between the eradication of the weevil and the advent of the stinkbug issue. We didn’t have any need for Bt. The only treatment you should need in cotton now is for stink bug. Stink bug isn’t a new pest — it’s just a pest that was created with the use of Bt cotton because it upset the natural balance.

Acres U.S.A. It’s fascinating how there’s this interaction of populations between the three “pests” — the boll weevil, bollworm and stink bug — and I’m sure others. They all balance out in systems that mimic natural environments — at least the native species. 

Lewis. Alton and I, and others, realized that after eradicating the boll weevil, if we didn’t take the opportunity to move to a full ecologically based system, we were missing the opportunity of our whole generation.

We had Bt cotton coming in, and we already knew they weren’t doing it in an ecological way. We were going to be in a situation where every crop was going to have pesticide sprayed from inside out, on the entire plant, 24 hours a day — and that was going to create some problems. They wanted to use the full force of pesticides all the time against the bollworm, which they wanted to eradicate. The idea was that we’d gotten rid of the weevil, and now we’d use Bt to eliminate the bollworm problem. 

When you don’t have Bt, and you have feeding activity by bollworms in the field, that stimulates the plant to start producing some nasty chemicals, in addition to the odors that they produce to recruit beneficial insects. Those nasty chemicals helps prevent the stink bug. It has a cross interaction. Not only does it slow down the boll worm — it prevents the stink bug from breaking in. 

But we are losing that attribute. Bt doesn’t reduce the amount of pesticides conventional farmers have to spray. 

Acres U.S.A. Can you talk a little bit more about plant signaling? I know some of your original work was about how plants signal to beneficial insects. 

Lewis. We realize now that what we reported beginning several decades ago — which we thought was so spectacular — is just the tip of the iceberg. The power of different defensive mechanisms and the interactions of all these different components is just miraculous. 

Our original vision was to identify these chemicals that help attract parasitic insects. We knew something was taking place, but we didn’t know what it was, nor the behavioral mechanisms associated with it. We had two approaches — one, which is very similar to today’s conventional mindset, was to identify these chemicals that draw the natural enemies and spray them on fields to pull in a lot of natural enemies. But then we realized that that would be disrupting the natural system. The chemicals would be going where there weren’t any pests. 

Our other approach was to mass rear the natural enemy and release them in fields. We ended up finding out that when you do that, they just leave the field, because they are not in the behavioral mechanism that they are when they’re working so powerfully. 

What we found out is occurring is that when the herbivore begins to munch on a plant in any way, the plant recognizes it’s under attack, and it does that by recognizing a chemical in the salivary secretions of the pest that tells them, “This pest is on me.” And then it cranks up a set of chemical factors inside that begin to emit body odors. It involves about six to 10 different chemicals. It’s like a barcode; the blend is unique for each different pest. They make these odors that recruit the beneficial predators. 

We found out that this chemical in the salivary secretions of the caterpillar is an elicitor. The beneficial insect not only knows something’s feeding on this plant; it knows what type of pest it is. You can see the value of that, because there’s several different kind of pests at any time. There’s aphids, there’s spider mites, there’s boll worms, and there’s different kinds of beneficial insects that are attacking. If they couldn’t tell the difference, they would be going to plants by mistake. 

This is a unique system — the plants are talking to the good guys and telling them “something’s feeding on me” — as well as what caterpillar it is, in order to attract the right beneficial. It’s a powerful system.

Walker. There are a lot of things that can turn this ability to sense and signal on or off in the plant. We know that certain insecticides will shut this down in the plant. The organophosphates just about shut it down. And then I have seen where we had too much nitrogen on cotton — that shut it down. The cotton would get 10 times as many insects on it as the neighboring cotton. Or in dry weather, if the plant was stressed, it would attract more insects. 

A healthier plant growing in a healthier environment is going to turn this mechanism on a lot more.

Lewis. Also, not knowing this mechanisms, we were not selecting for it in breeding. You can breed for a plant that does it strongly. We can also agronomically manage to optimize these mechanisms. We can do both. 

For example, we found out that some of the wild cotton that has escaped — it grows in different places in Florida as a little tree — some have tenfold the ability to emit these defense signals that recent agronomic cultivars do.

Acres U.S.A. I think one of the things that people might push back against is that if you’ve got a couple-hundred-acre field, how are beneficial insects able to get to the middle of the field?

Walker. Beneficials are very mobile. They fly for miles. They can get there. And you brought up a good point. We’ve spent 75 years destroying the system — it may not come back in one year. It does take more than one year. It takes many years to build it back up. I had a field that was a hundred acres, and I had no problem with it.

Lewis. But that’s a good thing to consider when you’re redesigning a farming system — you build these factors in, and you leverage these built-in strengths. That’s what we need to understand. 

These parasitic wasps are free living as adults. They use the caterpillar as a host to lay their eggs in. They have to have a nectar meal every now and then, and it turns out that the cotton plant has extra floral nectar under the leaf. We never really knew why that was. But that’s a very important food resource for the parasitic wasp. When plants are being fed on by a bollworm, an army worm, or whatever, the plant increases the flow of nectar, as well as producing the chemical signal to the wasp.

Acres U.S.A. How would you describe the difference between the system you’re describing and traditional integrated pest management?

Walker. Integrated “pest” management — that’s a misnomer if ever there was one. It’s integrated “pesticide” management. That’s all they’re trying to do.

Lewis. In IPM, they’re managing pesticides, not the pests. They count what’s out there and treat only when the threshold hits. But it’s just managing. They’re not choosing how to promote landscape ecology and the mechanisms that promote this system. 

Walker. Like most other new inputs, it worked very well at first, and farmers did reduce their pesticide use quite a bit. But after a few years, with resistance, they were back putting out the same number of insecticide as before.

Lewis. We’ve had it backwards for a long time. The first meeting of the southeast branch of the Entomological Society of America I went to was in Little Rock, Arkansas, in 1965, and almost every paper being presented was a new pesticide for this or that. That’s the way we manage pests — through pesticides.

Walker. What Joe and I, and others, are doing is trying to manage insect pests by keeping them there, year-round, at a sub-pest level — below the pest level. The pests are always there, but we are keeping them there at a level at which they are not pests.

Lewis. The question we always have to ask is, “Why is this pest a pest?” Because insects shouldn’t normally be pests. The fact that it’s a pest means something’s out of balance — unless it’s something like an invasive species. A pest outbreak of any kind tells you something’s wrong. Or, in some instances, you may be trying to grow something where it really doesn’t work.

Acres U.S.A. Have either of you ever experimented with boron applications for pest control?

Walker. We have boron deficiencies in both cotton and peanuts, and we do apply those, but not specifically for pesticide pest control.

Lewis. But you’ve talked to me about nitrogen, Alton — about how we use far more than what we need.

Walker. Yes, we’ve used more of that than we need. Since those crops are deficient in boron, we put it on to keep from stressing the plants, and no doubt balancing those nutrients will help reduce pests in the plant. 

Another thing is that we learned not too long ago what Roundup does to the system. Roundup reacts with our metals; the main one it reacts with and prevents plants from utilizing is manganese. We treat peanuts two or three times every year with additional manganese. Now this is also a problem in the cotton, but it doesn’t exhibit itself — we don’t see the problem of the discoloration in cotton leaves that we see in peanut. But the heavy use of Roundup tied up nutrients in the soil. This also goes along with raising the pH to above 6.5; the two together has really hurt the uptake of manganese.

Lewis. We haven’t looked at any of this kind of stuff holistically. Historically, a plant agronomist would study that, but a pest management specialist wouldn’t. We break it down too much into specialties. The agronomist may be managing the cotton plant in a way that will produce another quarter of a bale per acre, but maybe the crop loses a half a bail trying to control the pest outbreak. 

Walker. I think that once we get away from using pesticides and commercial fertilizers and we start to improve our soil help, we will not have to put on these specialty fertilizers like boron and manganese and whatever else. I think that the organisms will get these elements from the soil and move them to the plant roots and up the plants, and the plant will be able to balance themselves in the system. 

Another great advantage of this system, I think, is for cattle production. One of the big problems in cattle production is putting up stores for the winter. That is a huge cost in cattle production. We can eliminate lots of this by grazing our animals on these fields in the wintertime. I truly believe that if we had a diversity of animals on a cotton farm, a farmer could make a very good living on 300 acres. I made a very good living on 650 acres without livestock. This could help bring the communities back together in rural America. This system doesn’t work with huge farms; it requires more intensive management.

Lewis. Agriculture has gone in the direction of centralization and specialization in modern times, which means bigger farms and more specialty areas. Small farms — that’s how we are going to redevelop these rural communities. We need to support small, diverse, family farmers. We aren’t going to fix rural America by building more four-lane highways into these areas. That’s the kind of thing we hear folks in our state government talking about in. But that’s not going to build community; that can only happen ecologically.

Acres U.S.A. It seems like when you drive on a highway, there are far fewer bugs on your windshield than there used to be. Is this just anecdotal, and how much of a concern should that be to us?

Lewis. I’ve seen a couple of studies on this. There’s some places where they’ve done indexing. But at least anecdotally, this reduction in insect numbers seems clear. 

Walker. This is really a problem in a monocultural forestry system like I worked in. At least 80 percent of commercial forests are loblolly pine, and loblolly pine plantation is an ecological desert. There’s no spraying, but you get almost 100 percent shade — there’s almost no sunlight touch the ground. There are no other plants growing in a loblolly pine stand. There’s just the one species out there — almost no birds, no insects. We just have a few species that the modern system favors. Anytime you eliminate diversity, you favor some species.

Lewis. But also you favor upheaval and chaos. The way we farm is to clean till everything when we’re through with the cropping system, and throughout the winter there’s this eroding, empty field, and then we come in and plant around April to May, and we get explosive growth. There’s a lot of upheaval going on, and you don’t get equilibrium — you destroy it at the end of the year. 

Doing this in so much acreage creates a chaotic environment. I think it really affects the abundance of different kinds of natural insects. We may create a sudden increase of some pest for a period of time. It’s just upheaval. It’s a very changing dynamic. We don’t get equilibrium.

Walker. We see this in birds too. We probably only have 25 percent of the birds species that I saw when I was a child. Especially in urban areas. 

But this system I grew in works. It improves the quality of the crop, reduces pesticides and reduces erosion. Cotton is a unique crop. It’s struggling right now economically, and maybe it needs to struggle a bit more in order to change the system. If we got all the government subsidies out, the system would change immediately. 

Lewis. Bt cotton, which covers so many acres throughout a cotton belt, is meant to suppress the bollworm and the tobacco budworm populations. But the beneficial insects that depend on them — two of the main ones we studied are specific to those two species of insects. Their populations are getting really reduced. I could see one of them possibly going extinct in the U.S. as a result of Bt cotton. We don’t think very much about just how much this kind of technology impacts our ecosystems.