David Mortensen Interview
David Mortensen, Ph.D.

David Mortensen, Ph.D. interviewed by: Chris Walters

David Mortensen, Ph.D., is a professor of weed ecology at Penn State. Back in early 2012 he led a team of co-authors who produced a paper called “Navigating a Critical Juncture in Sustainable Weed Management.” The equivalent of an agricultural bombshell, it delivered unhappy news about the consequences of engineering crops to withstand more than one pesticide. Noting the remarkable ability of weeds to evolve resistance strategies, Mortensen and his co-authors predicted ecological disaster if crops engineered to permit the return of 2,4-D and dicamba are put into circulation. The article’s predictions of exponentially rising auxinic herbicide use were shocking until it emerged that the USDA’s estimates were even higher. Over two years later, as biotechnology’s latest assault draws closer to final regulatory approval or refusal, it seemed like a good idea to check in with Mortensen. Author of dozens of research papers, he is a veteran of decades working in fields alongside farmers in Iowa, Maryland, and many states in between.

ACRES U.S.A. What is the crux of the issue here?

DAVID MORTENSEN. This new technology that’s going to “save” herbicide- resistant crops — that is, the new stacked-trait herbicide-resistant crops — in my view is going in exactly the wrong direction. It’s going in the wrong direction for a number of reasons, not least of which is that if we adopt them we are going to double or triple herbicide use on our major commodity crops, corn and soybean, with significant increases in use on cotton. We tried to be conservative and careful in our Critical Juncture paper with that estimate of doubling and tripling herbicide use. We spent months debating that amongst the co-authors. Thus it’s intriguing for me to read in the USDA’s own assessment that we will increase use of auxinic herbicides four to seven-fold if we approve these new crops, as the USDA seems to be leaning toward doing. I find it bordering on maddening to think that’s an acceptable trajectory to put ourselves on. It goes against everything I’ve worked on for the past 30 years.

ACRES U.S.A. How did the current wave of weed resistance arise?

MORTENSEN. I would attribute the resistance problem that we have to packaging. What I mean by packaging is that you alter a crop, and you either own the crop seed or you have some sort of contractual arrangement with another company that owns the crop seed which has your trait — when that enables pesticide use, you now have a seed-pesticide input package. Glyphosate-resisting crops are the first example of such a package. You buy the crop, you almost certainly intend to use the matching herbicide for the package because you’re paying a higher cost for the crop — the “technology” fee — and then you buy the herbicide that goes along with the seed. There’s the package. There are all sorts of creative marketing schemes associated with packaging — you buy our crop seed, we’ll throw the herbicide in at a discount. You buy 1,000 acres worth of the total package and we’ll mark it down further than if you buy 500 acres’ worth of the package. All of a sudden you’ve got these crops with genetically modified traits in them that enable over-the-top pesticide use that would otherwise kill the crop.

ACRES U.S.A. What does that mean genetically?

MORTENSEN. When you lock the package together like that, you are amping up the resistance selection pressure. You’re almost guaranteeing that the same mortality source is going to be used on that field multiple times in a season. We know that’s bad for driving the rate of evolution of resistance, since you have multiple cohorts of the pest that encounter the pesticide. That creates a very strong selection pressure. Then we’ve done something that makes no sense to anyone who studies integrated pest management — we’ve put the same trait into the crops that we typically grow together in rotation. Not only do they have soybeans, but there is also Roundup-resistant corn. Then our more diverse dairy systems here in Pennsylvania now have Roundup-resistant alfalfa. You could easily have a farmer who does beneficial things with regard to rotation, who because of the package is locked into the same mortality source that selects for resistant weeds. This is overwhelmingly the driver accelerating the resistance problem we see today in agriculture.

ACRES U.S.A. Is that the only factor?

MORTENSEN. Another factor is that we’ve tended to move away from tactics we used in the past. A smaller percentage of farmers lean on those tactics as an integrated part of their pest management program — things like cover cropping, rotation, selective tillage and rotational tillage. These things are not part of the package, the herbicide-GMO gene insert system. As we’ve moved away from that diversity of tactics, the many little hammers, we’ve put more of the suppression and mortality pressure solely on the herbicide, which is another very strong selection pressure for resistant weeds to the chemical.

ACRES U.S.A. Does glyphosate have unique qualities that contribute to the process?

MORTENSEN. One of the worrying things we’re seeing — we talked about it in the Critical Juncture paper — is that because we’re using it so much, we’ve seen two kinds of resistance emerge to this herbicide. I don’t know whether it’s really fair to put this only on Roundup, but it’s definitely happening with Roundup-resistant weeds. One is the kind of resistance you would expect to see where you have a point mutation, something that’s really specific. It has to do with where the herbicide is affecting the site on the plant. In the weedy plants, that’s down to a very specific location the herbicide locks into and disrupts. The other kind is a more general resistance. As the plant evolves resistance to glyphosate, it likely will also be resistant to other things. These are more generic forms of resistance where plants can detoxify herbicides by what they call metabolic detoxification, and that is not limited to Roundup. When you have this kind of resistance in a population of plants, you’ll see a much more rapid evolution of resistance to other herbicides.

ACRES U.S.A. What is metabolic detoxification?

MORTENSEN. That’s where the plant is able to defend itself by breaking apart those bad chemicals. Plants, like the human body, have defense mechanisms. Our bodies can attack viruses, or they can deal through novel ways with certain compounds that are not good for us. We can destroy them and excrete them. All living organisms have different ways of defending themselves, and plants have certain kinds of enzymes that more or less attack chemicals and break them down. Now, with a herbicide that works well, it swamps any ability of the plant to do that, and it kills it. But if you keep using that same killing practice again and again, you’re going to select for certain individuals in the population that have a particular capacity to carry out the detoxification. Over time you select for resistance where those become the dominant genotypes in a population of plants. There’s something called P-450 oxygenase that’s like a general purpose detoxifying enzyme that breaks down lots of herbicides.

ACRES U.S.A. Were there any reasons to believe that glyphosate was a more benign herbicide than the ones that had been in heavy use in the postwar period? That was the shibboleth going around a decade or so back, that glyphosate really wasn’t as bad as the old weed killers.

MORTENSEN. There will be some debate about that, but I would say it was a fair claim. In my view, it is a more environmentally friendly herbicide than a lot of the other ones. That’s because of its structure, and its persistence in the environment is relatively short — that kind of thing. The thing that’s disturbing is that we’re going back to the old herbicides to save the herbicide-resistant crop technology. Some of our oldest herbicides are going to be the ones these stacked-trait crops will be resistant to, such as 2,4-D and dicamba.

ACRES U.S.A. What is stacked herbicide resistance? And what’s the flaw in the logic about the utility of stacked resistance?

MORTENSEN. An herbicide-resistant crop that’s genetically modified is selected for by taking genes from another organism — in glyphosate’s case it’s from a bacterium — and putting those genes into a soybean plant or a corn plant or an alfalfa plant. Then they sell the seed that has that gene insert in it, and the herbicide is used to kill the weeds. The stacked-trait herbicide-resistant crop has the glyphosate resistant trait in it, and then you add another gene from another bacterium, or another gene from another organism. But in these cases it’s a gene that confers resistance to a different, unrelated herbicide. Now the crop plant is resistant to glyphosate, and it is resistant to 2,4-D. It depends on the chemical and the marketing system for the seed-herbicide package. For example, according to the current Dow application for deregulation of Enlist soybeans and corn, those crops have been selected for glyphosate resistance, and the gene sequence for 2,4-D resistance is in those corn and soybean plants as well. Almost certainly the package will consist of the company mixing 2,4-D and glyphosate into a new product with those old active ingredients. So the package has been expanded from one herbicide active ingredient to two active ingredients. These will be applied probably at the same rate as the individual herbicide. This is where the doubling or tripling comes from in herbicide use, particularly if you start using it multiple times during the year. That’s what is being evaluated right now for deregulation.

ACRES U.S.A. Just for clarity, the return of 2,4-D and possibly dicamba is actually built into the marketing structure, which is in turn dictated by the genetic structure? The people doing this are planning as well as expecting a return to 2,4-D and possibly dicamba?

MORTENSEN. That’s it exactly.

ACRES U.S.A. How in 2014 are we still talking about 2,4-D? Wasn’t it outlawed in many countries and severely restricted here?

MORTENSEN. Actually it is used on certain crops, but it’s being used in a very limited way or it’s not being used at all. In some places it’s outlawed because of the high risk of injuring other crops and other nearby plants. Most of our major fruits and vegetables are very sensitive to 2,4-D and dicamba.

ACRES U.S.A. While we’re at it, why don’t we bring back ethyl gasoline? That was an equally wonderful product.

MORTENSEN. These old compounds are not widely used if at all in Europe, for example, where for six weeks this spring I studied at a university, working on this problem and related problems. Of course over there they think this is nuts. “You guys lost your minds? What’s going on?” These herbicides are very restricted in their use because of how active they are on other crop plants, and the potential injury to those crop plants. In our system I would say that’s the main reason why they are restricted.

ACRES U.S.A. Along with their vast potential for injuring people, which is not your area of study. But haven’t they designed a product that is self-sabotaging? First they said our product will help you use less herbicide, except of course you would use more glyphosate, the supposedly benevolent herbicide, meaning you’d help the environment in the long run. Now that weed resistance is raging, they’ve come up with a stacked-resistance idea, and it’s hard not to take a cynical view that the only motive here is to save the product. If it drives purchases of the older chemicals, too bad, but at least it’s driving loyalty to the monocropping and the input-intensive way of doing things. Is it fair to note a desperate quality in all this activity?

MORTENSEN. From a packaging point of view, you’re right. The argument early on was that you would use less, and that was also the argument being made about Bt crops. From a company point of view, if you own the germplasm and you own the traits and you own the herbicide, you can see the marketing capacity of such a practice. Then it goes from very small acreage to very large acreage, and you have this enormous market. You’ve got the seed, you’ve got the gene, you’ve got the patent, and you’re getting a royalty on the patent when the farmer pays the technology fee. You sell them the seed, and then you get the sale of the input that goes along with the package, so it’s all very tight. From that point of view it’s quite a marketing coup, and this was described comprehensively in a very nice book called Lords of the Harvest, authored by Dan Charles from National Public Radio about 10 years ago or so. Some companies initially thought “Wow, that looks like a public relations nightmare, to be tied to altering a crop that enables them to use more of our pesticide. How do you, how would we spin that in terms of marketing?”

ACRES U.S.A. How do you thread that needle?

MORTENSEN. As the resistance has developed and as the performance of the package has declined, there is no question that we’ve created a transgene- facilitated herbicide treadmill. At each click of the cycle, you put in a new gene and a new herbicide active ingredient in the product along with the old one. There are many patent applications in D.C. right now that are looking at two or three traits in the crop for different herbicides.

ACRES U.S.A. As a result can you safely predict either an exponential or incremental increase in selection pressure?

MORTENSEN. I wouldn’t say exponential, but I would say incremental increase. That’s what we’re doing, and it doesn’t make sense.

ACRES U.S.A. No, it’s kind of breathtaking in its counter-intuitive quality. Other than pure profit protection, it is incomprehensible that anyone would bring back these chemicals. Since we’re speaking in early June, when does this new phase of biotechnology make its debut?

MORTENSEN. Dow Agri-Sciences has applied for the green light to deregulate, which pretty much gives them the green light to commercialize and sell crops — soybeans and corn — that are resistant to glyphosate and 2,4-D. The Department of Agriculture and the Environmental Protection Agency will conduct independent, and unfortunately not independent, parallel reviews of aspects of the technology. Then they will make decisions on whether or not to approve the use of the herbicide in the case of EPA, and approve the use of the herbicide on the newly transformed crops in the case of the EPA and whether such use would select for new pests in the case of the USDA. APHIS — USDA’s Animal & Plant Health Inspection Service — will evaluate the actual germplasm, the new traits in the new crops. That’s in review right now, and some sort of regulatory decision will be made — either to deregulate or to not approve and require more data or whatever. Their decision will be made later this summer or early fall.

ACRES U.S.A. Then there is still some hope this idea will not hit the market?

MORTENSEN. Yes, there is some hope of that.

ACRES U.S.A. Integrated weed management and permaculture techniques have evolved over the past few decades without the benefit of large tranches of research money. What kind of further research is needed?

MORTENSEN. The farmers who read Acres are practicing holistic management, and they know there are solutions. Farmers have been developing and refining solutions for as long as farming has been done. Pest management keeps evolving, and where farmers have embraced a truly integrated approach to managing pest problems they’ve been at the forefront of designing resilient farming systems. They build redundancy into their systems so that if one thing fails, something picks up for it. We do that with rotation, we do that by taking the selective pressure for killing the pest off of one tactic. Agroecologists who study these things benefit a lot from working with farmers who are doing them — people like me, for example. I spend a lot of time at farmers’ places learning about the diversity of things they do. Then I go back and study some of those things in a lot of detail, and sometimes I can provide some insight about some aspect of those tactics that’s helpful or puts them back into a systems context. As a researcher who believes in participatory research, I think we arrive at robust solutions by working together and listening to the farmer and by embracing the idea that the system can help provide the pest suppression.

ACRES U.S.A. Could you give us a specific example?

MORTENSEN. For example, what are some things that folks who are hooked into this herbicide treadmill can do? One of the things I’ve been advocating as a workable fix for the first step toward greater integration of tactics is the use of cover cropping. There’s just an incredible body of evidence to suggest that cover cropping can play a very important role as a tactic, even in cropping systems where the rotational diversity is relatively low. So if someone wasn’t willing or didn’t feel like they could do anything else but add cover cropping to their system, I believe that alone would add a very significant edge in dealing with pest problems. As you and I and many farmers know, you don’t just do it for weed management, you don’t just do it for insect management — you’re getting a buildup in soil carbon, enhanced soil quality, nutrient retention, cleaner water running off the field, smaller amounts of water running off the field and increased weed suppression.

ACRES U.S.A. Following your lead here, intelligent cover cropping offers a lot to farmers who face the downsides of biotechnology?

MORTENSEN. Those are the kinds of practices that we really need to see among farmers who are struggling with the resistance problem and where their options have been narrowed by the pesticide crop seed package. That packaging is the antithesis of practices that provide multiple ecosystem services. It’s a practice that provides control — let’s stick the gene in, now we can kill those two weed species that have evolved resistance to glyphosate. That is such a narrow framing of how the system works — that we’re going to alter the crop genome, create a whole new set of products that provide a very narrow slice of one service to the farmer as opposed to the more integrated approach we’ve been advocating.

ACRES U.S.A. is always held up as a model of progressive systems’ thinking, and that’s where we need to be going. I think that it’s a struggle when you have folks who are in a box with systems that have become quite simplified with respect to tactics and integration of tactics. Build the tactics back into that system. It’s not an easy sell because you’ve got a marketing force that’s pushing this other approach.

ACRES U.S.A. Has any of your research focused in on the special challenges of detoxifying soil that’s been subjected to this technology for a number of years? What particular areas are you investigating in your integrated weed management research?

MORTENSEN. We’re one of the few labs that has looked at the offsite movement of these chemicals, using both fancy modeling as well as field experiments where we’ve created a type of drift to look at off-site movement events we fully expect will happen when these chemicals are used. If they are deregulated their use will increase four- to seven-fold, which is a phenomenal increase in the use of auxinic herbicides. On top of that, a lot of the application will happen in the middle of the summer, whereas most of the use now occurs in early spring when most plants haven’t leafed out yet. It’s a safer time of the year to use those compounds, at least with respect to how the plant reacts, because the plants are not yet active. But if you apply them in the middle of the summer when everything is leafed out and flowering, the chemicals will move away from the site more often on hot, breezy days. The other thing is that organisms on the landscape are much more vulnerable to the effects of chemicals in the middle of the summer. We’ve been studying what the effect is when they don’t stay where you apply them in a corn field or a soybean field — when they move into a field edge or onto adjacent grasslands or a riparian buffer along a stream bank.

ACRES U.S.A. What have you found?

MORTENSEN. What we’ve found is that they’re very active generally on broadleaf plants. It just happens that broadleaf plants are the plants that produce nectar and pollen-bearing flowers that attract beneficial insects such as pollinators and predatory wasps which provide bio-control services for insect suppression in the agricultural matrix, as well as pollination services to the vegetable and fruit crops. We’re concerned about the direct effects of the herbicides drifting into these other plant communities, hurting and killing those plants, reshaping the flora of the field edge and damaging the crop plants adjacent to the herbicide-tolerant crops. In addition to those direct effects, we’re very concerned about the indirect effects of taking the flowering plants out of the landscape so that the floral resources for these beneficial insects decline on the landscape, leading to the decline of services from those insects.

ACRES U.S.A. It is odd to hear you speaking of a research deficit, since the problems we’re talking about have been around long enough to have received intensive study.

MORTENSEN. When I say that we know very little about this, that’s the truth, because not very many people study it. However, the little bit of data that we’ve collected over the last five years suggests there’s every reason to be quite concerned about what’s happening. We’ve been beating the drum about how we need to understand this better before we unleash these practices, particularly when we suspect that they’re going to be used on a lot of acres. Again, that’s not just me saying so. That’s the USDA’s own assessment of this technology, a four- to seven-fold increase at a time when these organisms are sensitive to them in the field — they say there is something to be really concerned about. I personally do not study the fate of the compounds in the soil, in the crop fields that have been sprayed by the herbicide. Personally I’m very concerned about the kind of off-site movement that would be occurring and the effects of that off-site movement.

ACRES U.S.A. Then the salient point is that we still have a great deal to learn about the unintended consequences that might radiate outward from spraying sites where stacked-resistance products will be applied if they get into general use?

MORTENSEN. If you can imagine these debates unfolding in a room where most everyone in the room studies weed control, you know the general focus of that conversation is going to be on weed control. That crowd won’t tend to think a lot about the bees. It’s not a group that’s thinking hard about what’s happening to the predatory wasps that attack the aphids that eat the wheat plants.

ACRES U.S.A. Or the monarch butterfly?

MORTENSEN. Or the monarch butterfly. I organized a symposium on this whole subject with the Weed Science Society three or four years ago. I had a higher-up, a vice president from one of the big companies involved. In a large, packed room he stood up shaking his finger, pointing at me and shouting, “What do bees have to do with this?” I realized after I’d presented all this stuff that he simply didn’t understand that we have food webs in nature — that beneficial insects are also important, and they rely on flowers and pollen and nectar meals and that many of those are extremely host plant-specific. You take the host plant away and the insects go away. We work in apple orchards in Pennsylvania. This is a mind-blowing number — we’ve seen as many as 160 species of wild, pollinating bees in the orchard. Colony collapse that results from unhealthy commercial Apis mellifera can be offset for farmers by leaning on the wild bee pollinating community. So much so that in a third to 40 or so percent of the orchards in our largest apple producing county in Pennsylvania, the farmers themselves stopped using commercial hives to rely solely on the wild bee community for crop pollination. We have only recently begun to appreciate how important these insect-plant interactions are to a truly sustainable agriculture. On landscapes where we deploy vast acres of low crop diversity, all sprayed by the same herbicide chemicals that are active in the field and active in the adjacent fields, etc., there is a high potential to knock out those beneficial services from these insects. Our hope is that data from studying these effects helps to enlighten the review process that’s underway right now.

ACRES U.S.A. What are the other facets of your research?

MORTENSEN. More broadly, we do a lot of work on integrated approaches to pest management. It’s the antithesis of the transgene-facilitated herbicide treadmill that I’ve been describing. It consists of looking at cover crops, measuring ecosystem services, then looking at the combination of cover cropping and rotation. We do that on research farms where two women who work with me go to the farmers and perform something we call a rapid ecosystem assessment of the beneficial impacts of cover cropping those farmers are seeing, for example. They collect that kind of data as a way of facilitating knowledge exchange among farmers who use these diverse tactics in their approaches to pest management and systems management. That’s the kind of stuff that I do. Some of that work I do myself, and some of it I love doing with this next generation of thoughtful, forward-looking progressive folks.

ACRES U.S.A. You just made two profound points. One, that knowledge of something as basic as a food web can be totally lacking on the part of people advancing powerful, potentially harmful technologies, and two, that we have a surprising lack of knowledge about something just utterly crucial to our future.

MORTENSEN. We understand the direct effects of how these herbicides kill things in the field. That’s been studied by the companies, that’s been studied by land grant scientists, and there have been a lot of resources put into studying how active ingredient X controls the spectrum of weedy plants in a particular crop field. Precious little work has been done looking at the broader effects of these compounds on critical ecosystem service processes. So when we get regulatory decisions bearing on the benefits and risks of the technology, we have a pretty good understanding of the benefits with regard to how well it kills the weeds, under what conditions it’s most active, and that sort of thing. On the risk side we have a very constrained understanding of these practices. We measure things to conform to EPA requirements, a narrow slice of the effects of those compounds that misses things having to do with food webs. That’s just an example of it. What I’ve been arguing for is that when we make policy decisions about important changes in the way we do agriculture; we should do that with the right kind of data in hand or we’re going to make some mistakes. I’ve had some people respond to that criticism by saying, “Well, our system is set up so that if we release something and we make a mistake, we go adjust a couple things in the system and we make it better.” In other words, through a process of trial and error we’ll make the technology work. I’ve advocated that a more appropriate approach is to understand the broader set of impacts before we let these technologies out of the gate. Then we can perform the kind of risk/benefit analysis we really need before we make decisions.

ACRES U.S.A. You’ve been studying these topics for a long time. Have you noticed a shift in the arguments deployed in favor of biotech as time marches on and many downsides to the technology emerge?

MORTENSEN. We need a critical mass of people asking the broader questions about the systemic effects. It’s easier to get caught up in narrow pieces of things, to focus in on a specific tactic or a specific product. The statistical or experimental approach is easier — you put it in a spray tank and you mix it with a certain amount of water, then you apply it when there’s this many leaves on the crop plant, and this and that and the other thing. Then you publish that, and things are clean and they’re satisfying if you’re looking for clean results, but the reality is that when you start looking at things at the systems’ scale, they get messier. When we start talking about multiple tactics complimenting one another it becomes harder and harder, at least from a researcher’s point of view, to parse out which factors are contributing. When those interactions are context- specific — when this farmer’s farm or that landscape has more heterogeneity or more field edges in it than the next one over — you can study the effects of a chemical on the beneficial insect community without even realizing that at the scale of the landscape, the landscape will actually rule over what you would see in that specific set of fields. When you’re standing at the kitchen window and looking out onto a corn field that’s bordered by a forest, for example, the insect community in the field’s edge is dependent in part on the landscape fabric. And it goes right out the window. It’s not just the corn field, it’s not just the soybean field. All of this stuff gets messier. The error rate increases. I think the important point here is that nature is messy by design. The resilience of an intact, functioning ecological system arises from multiple processes occurring that contribute to pest regulation and the ecosystem service provision dynamics that we’ve been talking about. They’re harder to measure and many fewer people try to measure them. Honestly I think part of the reason is that it’s not even in people’s mind to measure them in the first place. Or even ask about the bees we’ll lose when herbicide drifts and we kill all the broadleaf plants in the field edge.

ACRES U.S.A. When research is hard to do, what is the biggest practical barrier you face?

MORTENSEN. It’s more expensive to do, and there’s only a subset of funding sources that will even consider it. That holds it back somewhat. Until we require such data before we make these important regulatory and policy decisions about the directions of agriculture — when we’re making a major directional change as we are with technology like this — I think it will continue being a struggle because of the reasons I just described. I am hopeful that I’m seeing more young people who want to do this work. I’m 58 years old, and I love working with bright young people. That’s one of the real perks of my job. This new cadre of ecologically minded agriculturalists comes with a cool kind of landscape perspective on things, and they want to get the kind of education that enables them to go out and do the messy stuff. Having more people doing the messy stuff is what we need to be doing. So I’m hopeful.

This interview is in the August 2014 issue of Acres U.S.A.