Better Know a Scientist: Weed Scientist Dr Lynn Sosnoskie

People: we’re in for a special treat today. One of my favorite tweeple, Dr Lynn Sosnoskie, has graciously accepted a Q&A for “Better Know a Scientist”. Dr Sosnoskie is a scientist at UC Davis’ Plant Science Department where she does research on weed control. She has a PhD in weed science from Ohio State and has done research at University of Wisconsin, as well as the University of Georgia.

I did a bit of crowd-sourcing and asked on my private Facebook profile what questions my friends and family would like to ask, and there were some excellent recommendations. My comments throughout reflect the fact that we installed fake grass in a good chunk of our yard after two trucks full of mulch created a weed-free, yet visually unappealing and fire-hazardous yard.  So here we go!

Q: Weed research seems to be a fairly random field to study. I don’t think I’ve ever met a kid or high-school student who dreams of becoming a weed researcher when they grow up. What led you to this field?

Dr Lynn Sosnoskie

A: It’s a long and random story, but I’ll try to sum it up nicely. As a biology major (during my undergraduate degree) we took a Botany class field trip to Longwood Gardens in Kennett Square, Pennsylvania. I fell in love with the place and, more importantly, fell in love with plant science. Following my graduation, I was lucky enough to intern at Longwood and a few other gardens/arboretums in the greater Philadelphia area. While attending a pest control lecture on dandelions, I just knew that I wanted to go further into the plant protection arena. After a brief detour (my MSc. in Plant Pathology), I was fortunate to get a research assistantship in a weed ecology lab at Ohio State, where I earned my PhD. I enjoyed my pathology years, but I was just always more interested in plant-plant interactions as opposed to plant-pathogen interactions.

[Biochica’s note: if only everyone was inspired by dandelions instead of being filled with rage...]

Q: What are you currently researching?

A: I have quite a few projects underway. Firstly, I am finishing up some studies looking at seed production in hairy fleabane (Conyza bonariensis) following failed herbicide applications. Hairy fleabane is a common weed in our orchard and vineyard systems in California  and many plant populations have developed resistance to glyphosate (which has been the most frequently applied herbicide in perennial systems). Hairy fleabane is a real bane to growers because it produces LOTS of wind-dispersed seed, which are responsible for both new and continuing infestations [Biochica’s note to Lynn: I see what you did there… “The Hairy fleabane is a real bane”... Awesomeness!!]. To return to my earlier statement about seed production following herbicide failures, I am interested in understanding how the plants that escape weed control efforts might affect the development of weed populations.

I am also looking at the growth and development of junglerice (Echinochloa colona), which is also a pest of California orchard systems (almonds, walnuts, pistachios etc..., under differing environmental and disturbance conditions to look at its potential to invade other cropping systems. A chunk of my time is also spent researching the biology, ecology and management of field bindweed (Convovulus arvensis), which is a significant problem in processing tomatoes.

Q: Why do some herbicides develop weed-resistant pests more quickly than others?

A: The development of resistance is a function of many different factors...the phenomenon really should be looked as an interaction between the weed, the cropping system, AND the herbicide. The simple answer to your question is ‘overuse of certain products in time and space’ and the simple solution, in turn, is that we should avoid using a single herbicide mechanism of action, exclusively, to control weeds. Yes, we have to ensure that we use our herbicides responsibly (see this post by Dr. Andrew Kniss (University of Wyoming)), but we also need to understand the current constraints on our cropping systems that might limit our abilities to diversify (see this post, also by Andrew Kniss). And let’s not forget the weeds, themselves. Certain biological characteristics appear to be more commonly associated with the development of herbicide resistance. Dr. Jodie Holt (University of California, Riverside) and some colleagues published an interesting paper in PLOS ONE looking at the ‘Taxonomic and Life History Bias in Herbicide Resistant Weeds’. They found that evolved resistance is more common in certain plant families (i.e. the Amaranthaceae, Brassicaceae, and Poaceae) than in others. They also reported that annual weed species were found more often in the list of weeds with evolved herbicide resistance, suggesting that the length of a species’ life cycle is a contributing factor. Although they didn’t have enough data to link other traits (i.e. seed production or outcrossing rate) to the development of herbicide resistance, many other sources have suggested that these characteristics can facilitate the evolutionary process.

[Biochica’s note to Lynn: does this mean that I can ask the spouse to go kill the weeds as soon as possible, because if he doesn’t they’ll evolve to become herbicide tolerant? Don’t answer that! That’s what I’m going to tell him...]

Q: What beneficial weeds do we often overlook when thinking about weeds?

A: I think the biggest beneficial weed on (almost) everyone’s mind is milkweed, which is a host for monarch butterflies. Many people might ask themselves: “Should I be actively planting milkweed on my property?” Only you can answer that question. Talk to your local extension agents or master gardeners if this species is an appropriate addition for your yard. At the very least they can direct you to the appropriate resources.

Q: How often have you had to say “No, I’m not *that* kind of weed scientist”? Do you have a poster of Cheech in your office?

A: A lot. Whenever one of my professional societies (California Weed Science Society, Western Weed Science Society, Weed Science Society of America) has a meeting somewhere, and people see our name badges, there is the inevitable “Wow. You must have some great parties, you know what I mean.” I do know what they mean and, sorry to say, they are likely to be sorely disappointed if they ever found out the truth about our parties (we just talk about weeds, the ‘boring’ ones). I do have a cheeky magnet from the city of Weed, California, on my filing cabinet, though.

[Biochica’s note: yeah… I’m going to need video footage of the next “Weed Science Society of America” conference. But I’ve got a nagging suspicion that it’s a “what happens at the conference, stays at the conference” kind of event *Wink, wink* ]

Q: Currently, there’s a lot of buzz surrounding “chemicals” in and on our food. Do you think that a world without herbicides is possible?

A: Is it possible? Sure. Don’t forget we farmed without synthetic, exogenous herbicides for millennia. And, despite what many might think, numerous weed scientists are looking at non-chemical strategies for weed control. For instance, in Georgia, we had a serious problem with glyphosate-resistant Palmer amaranth (Amaranthus palmeri). I worked with Dr. Stanley Culpepper (University of Georgia) to investigate the use of a fall tillage (soil inversion to a depth of 12 inches) coupled with a rye cover crop that we killed in the spring and used as a mulch to suppress Palmer seed germination/seedling emergence. Using  this strategy, we were able to reduce our in-crop Palmer amaranth densities by 90% or more. Now, we weren’t completely free of herbicides, but we did reduce the selective pressure that we put on them. As another example, Drs. Steve Fennimore and David Slaughter (University of California, Davis) are doing some really great work to develop automated weeding machines to use in high-value specialty crops (which have a limited number of herbicides available to them). However, with respect to your original question (Do you think that a world without herbicides is possible?), I’m going to have to say no… at least not at this time. We (weed scientists) are working with growers to diversify their weed production practices, but many do not have the money, the labor pool, the infrastructure, etc that will allow them to abandon herbicide use completely. Herbicides are a tool and our goal is to help growers use as many tools as are appropriate in their systems both safely and effectively.

[Biochica’s note: The Food Babe disagrees with you: no amount of chemicals is acceptable. Ever. Your nuanced explanation with references carries little weight when the Food Babe has spoken on the topic.]

Q: What are some of the more effective ways to get rid of weeds?

Lynn's picture of Bindweed

A: The answer to that question will depend on more than a few criteria, such as: what is the weed you are trying to get rid of, where is the weed located, and how hard do you want to work at getting rid of it, to name just a few. The most effective weed management strategies that might be employed in one’s backyard may be very different from those used by a commercial grower. For example, in a small patio space, hand-weeding is a viable strategy...the same is not true for thousands of acres of soybean. But all weed control strategies can be grouped into a few general categories: 1) exclusion or preventative measures (i.e. preventing weeds from entering your system), 2) physical disturbance (i.e. hand-weeding and cultivation), 3) obstruction (i.e. the use of a mulch or other time of barrier), 4) cultural practices (i.e. using crop rotation to manage weed populations), 5) biological control (i.e. allowing sheep to graze on edible weeds), and 6) chemical control (i.e. using a synthetic or organic herbicide to disturb plant growth and development). Ideally, we would encourage anyone/everyone to make use of as many strategies as are appropriate for their system. And, remember, you don’t have to figure this all out by yourself; your state extension personnel are there to help you with these kinds of decisions.

[Biochica’s note to the spouse: there are weed control strategies other than mulching!!]

Q:  Are there any new, more selective (and perhaps safer) herbicides in the pipeline?

A: I always tell my growers that they shouldn’t rely on the introduction of a new herbicide for weed control. We saw an abundance of products being released in the 1970’s and 1980’s, however the number of new discoveries has certainly plateaued. I don’t work for a chemical company, so I don’t know what the research pipelines look like, currently. If I had to speculate, I would suggest that the corporations are putting more money into crop trait development and big data. Assuming that we aren’t going to be getting a new herbicide product anytime soon, I think that we need to become smarter about how we use the ones that are available to us. For example, improved knowledge about weed biology and ecology will helps target weeds at the more vulnerable parts of their life cycles; in doing so, we will maximize the use of our herbicide tools and, hopefully, use them less frequently.

[Biochica’s note to Lynn: chemical companies should get into the astroturf business. Best weed-control system in California!!]

Q: Dr Andrew Kniss wrote an awesome post looking into that meme that I keep seeing on Facebook, about how vinegar+soap is “better” than Round-Up. He concludes that Vinegar+soap has a more toxic profile and is also more expensive. What often heard myth about weed science would you like to dispel if you could?

A: That we are only interested in applying herbicides. Yes, herbicides are useful tools, but weed scientists study/evaluate a wide range of management strategies. For example, I have worked, and still work with herbicides, but I have also been involved in other research projects looking at the effects of tillage, crop rotation, and cover crops on weed suppression and changes in weed community composition and structure. My colleagues at UC Davis and other institutions are engaged in many fascinating projects designed to further our understanding of weed biology and ecology, resistance evolution, and precision agriculture with respect to weed control.

[Biochica’s note to Lynn: my backyard is open to UC Davis plant community to study the impact of concrete and astroturf on weed development. I've actually had a few weeds make their way through!! I have created superweeds!!]

Q: You are stuck on an island and about to go insane from boredom. A genie suddenly appears and gives you the following choices (you have to pick one): a) an iPad with infinite battery life where your only App is Twitter and it's locked so you can only follow Nassim Taleb or b) A copy of "Seeds of Deception" by Jeffrey Smith. Which do you pick?

A: Taleb’s twitter feed. Although I disagree with his stance on GMOs, and often find him to be rude, there is interesting dialogue to be had.

Review of "Compositional differences in soybeans on the market: Glyphosate accumulates in Roundup Ready GM soybeans"

Soy bean field with irrigation system.
Wikimedia Commons. Image by Dwight Burdette.

A friend asked me to review the paper entitled "Compositional differences in soybeans on the market" (free available here), so I thought I'd make my comments publicly available. I'm going to read the paper first, provide comments as I go along, and then find reviews online (if any exist).

The paper starts by outlining the principle of substantial equivalence, meaning that GMOs have the same nutritional content than their unmodified counterparts. The authors outline that studies examining substantial equivalence for Round-Up Ready soybean were performed early on, but not when treated with Round-Up. A follow-up study found substantial equivalence when the soy was sprayed with Round-Up, but didn't examine how much glyphosate accumulated in the plant. It is the authors' hypothesis that this is a flaw and their study is designed to examine this question (i.e. is GMO Round-Up Ready soy substantially equivalent to its non-GMO counterpart when sprayed with Round-Up, and how much Round-Up accumulates). They hypothesize that high levels of glyphosate may affect plant metabolism. The authors point out that USDA data highlights that glyphosate use is increasing, so this question is all the more important.

I pause here to note that the authors do not clarify if this is glyphosate use per acre, or total glyphosate use. If I owned a house with 0.5 acre backyard ten years ago and now owned a house with 10 acre yard, and I used weed killers on both properties, then of course the total amount of weed killer I used would show an increase, simply because I have more land. But that may not mean that I've been using more weed killer per acre.

In their study, they examine 31 samples of soybeans grown in the state of Iowa to examine their two questions. They examined 3 different types of soy:
1) Round-Up Ready Soy
2) Conventional Soy possibly sprayed with other pesticides
3) Organic Soy bean which would have no glyphosate residues

The authors then list the variety of soy bean and how they were grown. They collected 3 kilos of soy from 31 different farmers, and it seems very odd to me that they'd select different varieties of soy and different methods of treatment for each category. Why wouldn't they try to find 31 farmers that used the same type of seed? The authors don't specify if the conventional soy is the isogenic variety to the Round-Up Ready soy. This is a key issue given the question they're trying to answer: for example, if I did a study on apples and collected apples from 31 different farmers, you'd want them all to be of the same variety rather then having some Red Delicious, some Fuji, etc.  Otherwise, it's not really an apples to apples comparison. Ha!! Get it???

So, they did a bunch of analyses on the soy beans. They found residues of glyphosate and one of the compounds it breaks down into in all the GM-soy, but not the conventional or organic (oddly enough, their graph doesn't have error bars...). Then, they did statistics on nutritional content and the authors highlight some of the differences (it's also worth nothing that they highlight measurements where the organic category had higher measurements, but not where GM/conventional had higher measurements). The authors then cluster the soy samples based on the results and find that the three different categories tend to group together.

Then the authors go on to reject the null-hypothesis of substantial equivalence. They highlight that their paper identified glyphosate residues in the crops at higher levels than had been hypothesized. They highlight the "toxicity" of Round-Up by citing Seralini (minus 200 points for citing Seralini).

My main comment, as I've mentioned in the past, is that substantial equivalence does not mean identical: "Substantial equivalence is often confused for identicality, however, the Food and Agricultural Organization of the United Nations states that substantial equivalence “is established by a demonstration that the characteristics assessed for the genetically modified organism, or the specific food product derived therefrom, are equivalent to the same characteristics of the conventional comparator. The levels and variation for characteristics in the genetically modified organism must be within the natural range of variation for those characteristics considered in the comparator and be based upon an appropriate analysis of data”" (emphasis has been added)

Also, the levels of glyphosate are provided and the authors point out that these are below the maximum permissible levels. So I'm not sure what their problemo is.

So, I searched for reviews of the paper and found one on GMOanswers, written by someone at Monsanto. They too, made the same criticism as me about the seeds: "When the authors collected the soybean varieties for this study, they separated them into the three groups — organic, conventional and GM. Unfortunately, each group contained different soybean varieties, with no overlap (with one exception) of varieties between the three groups, so each group was already inherently different from the others. Even the authors acknowledge that different varieties can have widely different seed composition. Therefore, concluding that any differences between the groups in this study were due to the way the soybeans were grown (organically or not), or the presence/absence of a glyphosate-tolerance gene in the GM varieties, is simply not possible. The three groups are expected to produce different results because they started out with different genetics."

GMOanswers also notes the fact that they were grown in different farms: "Since the plants in this study were not grown together but rather taken from separate fields across a region spanning a 200 km radius, any real differences between the three groups can’t be separated from the variation caused by location, and no reliable conclusion about their nutritional quality can be made. To put this in context, we are looking at satellite imagery to help farmers make more-informed decisions by increments of meters, not miles." I agree with this point, but having a bunch of crops that were grown in the same area could have provided some information if they were the same type of seed. But since they weren't, the different farms makes matters only worse.

GMOanswers puts the findings within the context of natural variation, which I appreciated: "Finally, when we take into account the effects of genetics and location, we see that the compositional differences the authors observed in this design are not unexpected. Protein levels in soybeans generally average ~40 percent dry weight (dwt) but have been shown to range naturally from 34.1 to 56.8 percent dwt (Wilson, 2004). This natural variability can be due to variety, location or environment, and it means that people are already consuming soybeans with larger variability than the differences in soybeans reported here."

The reviewer also notes that glyphosate residues were within permissible levels and then there's a blurb about the safety assessment of pesticides, yada, yada, yada... He also noted the slant that the authors have in not really discussing what pesticide residues in organic food means.

Amelia Jordan, whom I've interviewed in my series "Better Know a Scientist", did a review on Skepti-forum, and highlighted several other issues: the fact that there's no information on how the organic crops were treated, how the soil was treated in any of the farms, and very importantly, the
fact that 31 samples for a study with this much variability in a number of factors is very, very low.

All in all, I don't think the study is conducted well enough to draw any meaningful conclusion, especially not the one that they're trying to draw which is that organic food is "better" than GM. Their finding about glyphosate is interesting and I think that future studies that examine compositional differences between pesticide/herbicide tolerant crops and controls should do similar analyses, but the measurements in this study have been deemed to be safe.