Beet flowers and seeds, originally from ‘Koehler’s Medicinal-Plants’ circa 1887, via Wikipedia.

Beet biology

Sugar beets are biennial, which means they need two years before they reach maturity. During the 1st year, the plants produce a large root that, when dried, is 15-20% sugar. During the 2nd year, the plant uses those stored sugars to produce flowers and then seeds. Sugar beets harvested for sugar, therefore, don’t produce flowers or pollen or seeds.

Sometimes a few plants will “bolt” or flower when they aren’t supposed to, such as when there are unusual temperatures. This happens in both GM* and non-GM beets. Modern beet varieties have been bred to not bolt. In Europe, weed beets can pollenate beets grown for seed, resulting in weed x cultivated beet hybrids that might bolt, but in the US weed beets are not a problem. There is a very low percentage of bolters in any beet field – fewer than 1 per 1000 square meters of field. Another source of pollen could be beets or pieces of beets that are can be missed during harvest. These can flower during the following year as volunteers.

Bolters must be dealt with immediately, usually by removing them by hand. In the case of Roundup Ready beets where Roundup can be used to remove bolters. They have to be removed because seed from the bolters can grow into plants that harbor disease, and cause other problems. Some discussion on bolter control can be found in the University of California Cooperative Extension Sugarbeet Notes.

When they do flower, such as when beets are grown for seed, sugar beet pollen is fairly mobile, according to the Jan 2009 Pollen dispersal in sugar beet production fields. It is carried by the wind and possibly by insects as well. They found that pollen carried up to 1200 meters (that’s about 0.75 miles). These results are fairly consistent among papers testing dispersal of beet pollen. Even though pollen can move from field to field, most of it stays put. In the 1967 Cross-pollination between fields of sugar beet, the amount of pollen falling from one 20 acre beet field onto another that is 1000 meters away is estimated to be 0.004 compared to the amount of pollen coming from the field itself. Beet pollen can remain viable for a while when stored cold and dry in a lab refrigerator, but in the field it’s only viable for about 24 hours after it is shed by the flower.

Even though there’s all of this pollen flying around, most of it falls close to the parent plants. This is a good thing for any farmer trying to grow seed, or it would be impossible to produce seed with the genetics that they want.

Sugar beet by Mary Claire Garrison, via North Carolina State University.

Pollen potential

There are 4 situations I can imagine for combinations of GM and non-GM sugar beet fields. Only one is a problem because the seeds of sugar beets grown for sugar are irrelevant. You can not both harvest the root for sugar this year and harvest the seed next year. Even if a flower from a plant was pollinated with pollen that contains a transgene, the beet from that plant will not. So, there is no risk of contamination of non-GM beets with GM beet pollen – except in the case of seed production.

1. Two fields growing beets next to each other, one GM and one not GM. In this case, the only pollen around will be from bolters. Even if flowers are produced and are pollinated with pollen that has a GM gene, the root is still not GM.
2. A field growing non-GM beet seed next to a field growing GM beets. The only GM pollen around will be from bolters. It is possible that pollen from GM bolters could fertilize the non-GM beet flowers at a very low rate. Appropriate distances must be maintained by the farmer growing the seed to ensure he will produce seed with the genetics he wants.
3. A field growing GM beet seed next to a field growing non-GM beets. As in case 1, the roots in the non-GM field will not be affected. Just like in case 2, the farmer growing seed needs to maintain appropriate distances to protect her flowers from bolters to ensure her seed will have the genetics she wants.
4. Two fields growing beet seed next to each other, one GM and one not GM. This is where things get a little more complicated, just because there’s more pollen around. Since most beet seed is grown in Willamette Valley in Oregon, the potential for cross pollination is fairly high. The problem isn’t unique to GM, though.

Table beets via Wikipedia.

Sugar beets, table beets, and chard are all grown for seed in Willamette Valley, and they are all capable of cross pollination. Seed producers of any of these must keep their fields separated by distance from any other seed producers or the resulting seed could be worthless.

For example, if red table beet seeds were grown too close to sugar beet seeds, the sugar beet seed grower could end up with red sugar beet seed. Whoever bought and planted that seed would end up with a worthless crop, since all that red pigment would complicate sugar processing. Even if only a small percentage of the field had genes from table beets, the farmer would be paid less for his crop since the sugar processor would have to find a way to remove the red sugar beets. Table beets growing from the contaminated seed would likely have issues as well.

You gotta keep ‘em separated

Producing pure seed isn’t an easy job. Without GM even entering the discussion, there’s a lot to do to make sure that the seed a farmer buys is going to produce the right plants. In the case of beets, the plants are often weeded by hand to remove any plants that don’t look like the rest. The American Crystal Sugar Company has an excellent webpage that talks about sugar beet seed production, with pictures. For a non-beet centric view of how complicated it can be to produce good seed, the Seeds of Change seed company has a great article: Redefining Seed Quality. The article is about organic seed but applies equally to all seed types (there is one error in this article, see the next section of this post for details).

How do seed producers in Willamette Valley and elsewhere keep pollen from sexually compatible crops from pollinating their flowers and contaminating their seed? It all comes down to distance. The Oregon Seed Certification Service recommends different distances for stock seed and for certified seed (see the Oregon Seed Certification Service Handbook for more details on types of seed). Oregon’s sugar beet certification standards sheet (pdf) lists the following distances  for stock and certified seed production:

1. From sugar beet pollen source of different or unknown ploidy: 5000 ft, 3200 ft
2. From sugar beet pollen source of similar ploidy or between fields where male sterility is not used: 3200 ft, 2600 ft
3. From other pollinator or genus Beta that is not a sugar beet (including fodder beet, red beet, swiss chard): 10,200 ft, 8000 ft

Remember, 5,280 ft is a mile, so this standards sheet is saying that seed production fields need to be 1 to 2 miles apart (the American Crystal Sugar Company site says the distance needed might be “several miles”). If this distance works well enough to keep all the different varieites of sugar beets, table beets, and chard genetically pure, then it will work to keep GM genes out of non-GM crops. Pollen from a GM plant is no different than pollen from a non-GM plant. While I could understand if someone advocated for tests with GM pollen to determine the exact distance, I don’t think that’s necessary since we already have a lot of information on how far apart fields need to be to prevent gene flow. We just need to ask seed companies what they have found to be effective.

Don’t panic, it’s organic

The Redefining Seed Quality article has one little mistake. It says “By law organic seed can not contain genetically modified organisms (GMOs).” This is a common misconception. The law actually says that GM can not be used in organic seed, not that it can’t contain GM seed. The organic standards are processed based, not content based. As long as an organic farmer sources seed that isn’t GM and makes a reasonable effort to prevent GM materials from being in his products, organic certification will not be affected, even if the product is tested and found to have a GM gene in it. How can this be? Those reasonable efforts work the majority of the time because they are based on sound science.

The regulation isn’t completely clear on how all this works, so we can’t really blame Seeds of Change for assuming that the law says seed can’t contain GMOs. Back in 2004, USDA official Bill Hawks responded to questions about organic certification and GM by Gus Douglas of the National Association of State Departments of Agriculture. The excellent questions were met with excellent responses and really clears up what the policies are. The letter isn’t long, I recommend reading it in full.

This point of GM content is very important in the case we’re discussing here. If an organic beet or beet relative seed farmer (or any organic seed farmer) takes reasonable precautions, such as the appropriate distances as discussed above, it is still possible for cross pollination to occur at some low level. What level is acceptable? The regulation doesn’t say, because content isn’t the issue.

Of course, even though content isn’t the issue for organic certification, some people want to add extra levels of testing and certification beyond organic standards. The Non-GMO Project is a private labeling program that has established its own guidelines for what level of GM content is too high to allow use of their proprietary label. The Non-GMO Project Working Standard sets the following levels as the maximum allowable GM content: 0.1% for seed and other plant propagation materials, 0.5% for ingredients of human food, supplements, or hygiene products, and 0.9% for animal feed and supplements. These levels may or may not be met by the precautions required for organic certification, so farmers looking for a Non-GMO or similar label may need to take additional precautions.

Distance as mitigation strategy

As labels like Non-GMO become more widely used, more farmers will be testing their crops, so there is potential for economic harm due to even low levels of cross pollination. Still, none of this justifies a nationwide ban on GM sugar beet seed production. There are other options. Some would put the onus on the sugar industry and farmers who want to grow GM beet seeds, others put the onus on farmers who want more strict pollen control. Unfortunately, all options will make things difficult to varying degrees for one or the other, which I suppose is why the issue ended up in court instead of peacefully decided.

Judge White may not have known about distance as a mitigation strategy. If he had, perhaps he could have ruled that GM seed production could only take place a certain distance away from the fields of farmers who don’t want even the potential of GM pollen. I’d imagine there could be a legal argument that farmers using existing methods have certain rights when faced with a new method that could potentially affect their livelihoods. Setting such a distance may well effectively ban the growing of GM sugar beet seed in Willamette Valley.

Another option that was available to Judge White was to just prohibit GM beet seeds from being grown in Willamette Valley. There’s already a ban in all of Oregon against growing any canola (GM or not) because of concerns that the canola will pollinate other brassica crops grown for seed, like broccoli, although that concern might not be warranted, according to farmer Dean Freeborn in Farmer pushes for relaxation on canola rules. This could be used as precedent to justify a ban on GM sugar beet seed production in Willamette Valley, or even in all of Oregon.

Since Willamette Valley is apparently the best place to grow beet seed, a true ban or effective ban would likely harm the sugar industry and even farmers who don’t currently supply niche markets if the GM beet seed has to be grown elsewhere. I’m not sure what the law says about preferring one industry over another, but I think an argument can be made here.

Aside from the negative effects on the non-specialty seed market, there is another problem with distance. It requires, in any way I can think of it, that exact locations of fields be made public, at least to other seed farmers. From there I bet it wouldn’t be too hard for destructive activists to start pulling up plants or setting fields on fire. It’s an unfortunate reality that has to be dealt with.

Other mitigation strategies

If not distance, seed producers always have the option to use mobile, temporary tents over the plants while they are receptive to pollen. According to Seeds of Change, tents or field covers have a lot of advantages, including protecting the plants from insects and other pests. Here in Ames, Iowa researchers from USDA APHIS use tents made of fine mesh so the wind and sun can pass through while isolating the plants from undesired pollen. Of course, this would be a hassle for growers that don’t currently need to use them.

Another option is to use varieties that aren’t sexually compatible with your neighbor’s crops. Without going too much into detail, some varieties of beets have genes that only allow pollination with pollen that has a compatible gene. All the pollen in the world could be flying around, but only sexually compatible pollen would successfully fertilize flowers.

Another solution was suggested, briefly, by the (former?) Board President of the Organic Seed Growers and Trade Association Frank Morton in a post titled GMOs at the Door:

Some [mitigation strategies] are so obvious that it seems negligent to have not employed them, like using male-sterile maternal lines to carry the RR-genes (so no RR-pollen is created) in the hybrid seed production process (all GM-sugar beets are F1 hybrids).

This idea isn’t new, and works for many more crops than just beets. As described in The use of cytoplasmic male sterility for seed production (paraphrased from pdf, page 630):

CMS is used to produce hybrids of both table and sugar beets. Sugar beets are almost exclusively hybrids in the US and Europe, with some open-pollinated cultivars grown in regions of the world with lower inputs such as Morocco and Egypt. Approximately 50% of table-beet cultivars are hybrid; OP cultivars are still produced with the advantage of cheaper seed. CMS and its potential to be used to create hybrids was described in 1945.

Since hybrids are already used, it wouldn’t take much more effort to develop male sterile lines that carry the transgene. It does take some breeding work, which might be why beet seed companies who are licensing the Roundup Ready trait haven’t done it yet. Male sterile plants make a lot of sense for hybrid production in general, doubly so when dominant transgenes like Roundup Ready are involved.

This strategy is a win-win. Farmers of non-GM seed avoid any additional problems with cross pollination, all seed farmers keep using distances for isolation just as they always have, the sugar industry and sugar beet farmers get all the GM sugar beet seed they want… Once this economic cross pollination issue for seed production is resolved, there’s no reason to stop the deregulation of GM sugar beets.

Sea spinach by Squirmelia aka Jodi via Flickr.

A history of beets

Sugar beets don’t appear in nature, nor table beets. Ancestors of beets were domesticated from a seashore living species that distributed its seeds in corky fruits that floated in the water, called sea beets or sea spinach today. By ancient times, the plants were bred into something like Swiss chard, widely grown in gardens and considered to be a very healthy addition to the diet. The plants even appeared in ancient literature, such as in this culinary quote from The Acharnians by Aristophanes circa 425BC:

Beets and beet greens remained popular throughout the centuries. In 812, Charlemagne issued a decree that imperial estates include beets in their gardens, referring to a plant similar to table beets in that both leaves and roots can be eaten. In 1538, several varieties of beets were described by Andrea Cesalpino, an Italian botanist, in De Plantus. In 1600, the sweetness of beets was praised by Oliver De Serres, a French agronomist, in Théatre d’agriculture.

Finally, in 1747 Andreas Sigsmund Marggraf reported to the Prussian Academy of Sciences that he had extracted pure sugar from beets! However, the sugar was only about 1.6% of the total beet weight, which seemed too low to bother with. His student, Franz Carl Archard, working with white beets used for animal feed, developed the highly sweet White Silesian beet. Franz went on to open the first sugar beet extraction plant, and the rest is history.

Historical information is paraphrased from Sugar Beet by A. Philip Draycott.

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*GM stands for genetically modified or genetic modification.

Note: Much of this post originally appeared as No risk assessment for sugar beets? but has been edited to be a broader discussion of sugar beet biology, with additional discussion of seed production. The historical part was just incidental, I found all of this cool information and just had to include it. I hope you’ll think it’s cool too!

Does changing the sugar actually make the product healthier? Unfortunately, no. Because HFCS is sweeter than cane or beet sugar, more calories of sugar have to be added to achieve the same level of sweetness. The only thing that would make a product healthier is to reduce overall sugar content. This is especially true because cane and beet sugar as well as other caloric sweeteners all contain fructose, which has been correlated with or directly connected with a variety of health problems.

Over at Science-Based Medicine, Dr. Jim Laidler (an accomplished physician turned researcher) has written High Fructose Corn Syrup: Tasty Toxin or Slandered Sweetener? It’s a very informative post, one that anyone with concerns about HFCS should read and share! He concludes that fructose is something to be concerned about, but that’s only part of the story:

For people who are worried about their health or their children’s health — and who isn’t, these days — the data suggest that the best choice is to reduce intake of all sweeteners containing fructose. That includes not only the evil HFCS, but also natural cane sugar, molasses (which is just impure cane sugar), brown sugar (ditto) and honey. Even “unsweetened” (no added sugar) fruit juices need to be considered when limiting your family’s fructose intake.

Finally, the best nutritional advice is to eat everything in moderation — and that includes sweets. While a diet high in fructose may increase your risk of obesity, diabetes and heart disease — maybe — a fructose-free diet is not guaranteed toprevent those diseases. Eat a variety of foods, including a small amount of sweets, get enough exercise, watch your (and your children’s) weight and see your doctor for regular health check-ups.

And stop worrying that HFCS is poisoning you and your children.

Practical concerns are not the only reason to label or not label foods, however. Ethics definitely comes into play. Do people have a right to labels, such as labels that indicate a product contains ingredients derived from genetically modified organisms?

Chris MacDonald

Chris MacDonald, Associate Professor in the Philosophy Department at Saint Mary’s University, has written about the ethics of labeling GMOs at The Food Ethics Blog: Should Companies Label Genetically Modified Foods? and in a peer-revied paper Corporate Decisions about Labelling Genetically Modified Foods in the Journal of Business Ethics. The full paper is well worth reading, as is the blog post, but I’ll summarize (and editorialize) a bit here.

Chris argues that corporations should only be compelled to label if the product meets any of the following criteria:

1. A law requiring it;
2. A serious threat to human health;
3. Recognition within the industry that labelling made sense as a shared way of doing business; or
4. A consumer right to the information.

Of course, a law is not warranted unless one of the three other criteria is met, but based on our standards of ethics, individuals and companies are ethically bound to follow the law.

As Chris his co-author Melissa Whellams describe, the Canadian government passed the Standard for Voluntary labelling and Advertising of Foods that are and are not Products of Genetic Engineering in April 2004 in response to consumer requests for labeling.

The voluntary nature of the Standard essentially puts the onus of labelling back onto food producers and manufacturers. Current legislation under the Canadian Food and Drugs Act requires that all foods, including GM products, be labeled where potential health and safety risks (e.g., allergens) have been identified, or where foods have undergone significant nutritional, or compositional changes. Since Health Canada has deemed GM foods to be safe, companies are not required to label products as genetically modified, but under the new Standard, companies may voluntarily label their foods as products of genetic engineering.

While the Standard was being drafted, some stakeholders argued that GMOs are a “like to know” issue and that a “Contains GMOs” type label would simply be confusing to consumers, possibly mistaken as a warning. Other stakeholders argued that GMOs are a “right to know” issue, which is where ethics comes in. Do consumers who want to know if products contain products of genetic engineering have rights that trump the rights of consumers who don’t care? What about farmers, distributors, grocers?

Chris and Melissa argue “that although unilateral action in this regard might be admirable, an agri- food company has no ethical obligation to label its GM foods, given the current social, legal, scientific, and economic context.” This includes no ethical obligation to the consumer.

How can this be, when arguments for labeling of GMOs are often rooted in rights, including the important idea of autonomy? Chris and Melissa explain autonomy ”as involving morally important kinds of control over one’s life.”

We might then say that a person has a right to X (some bit of information, in the case at hand) where X is a prerequisite for effective exercise of autonomy, i.e., for effective decision-making regarding matters about which it is morally good that I be able to make decisions.

For example, most of us agree that we have a right to know information about a diagnosis that would help us to make informed decisions about medical treatment options. This is in contrast to the way healthcare was done in decades past, where patients assumed the doctor knew best.

Despite the arguments of labeling advocates, there is no such agreement about right to know for non-health related information when it comes to food. For example, despite the importance of freedom of religion in the US and Canada, no one is arguing for mandatory labeling for non-health religious reasons. We expect people who want to keep Kosher to seek out Kosher foods themselves. If religious or spiritual food needs aren’t considered a right, why would any other “desire to know” be a right? Perhaps this will change in the future, as “desire to know” became “right to know” in health care, but until then, governments and corporations are under no ethical obligation to label.

In another post, Chris argues that in the case of Trans-fats, there does seem to be sufficient threat to human health to warrant mandatory labeling, in contrast to the lack of harm shown by genetically engineered crops. In another post, Chris addresses the idea that environmental concerns are enough to warrant labeling, arguing that the concerns aren’t science based and that labels wouldn’t actually decrease environmental harm anyway. Besides, we know that genetic engineering is less harmful to the environment than other agricultural practices that aren’t labeled.

*Chris is also the Coordinator of SMU’s M.A. Programme in Philosophy and a Nonresident Senior Fellow at Duke University’s Kenan Institute for Ethics. He serves on the Editorial Board of the Journal of Business Ethics and has been named one of the 100 Most Influential People in Business Ethics two years in a row by Ethisphere magazine.

MacDonald, C., & Whellams, M. (2007). Corporate Decisions about Labelling Genetically Modified Foods Journal of Business Ethics, 75 (2), 181-189 DOI: 10.1007/s10551-006-9245-8

we reject the organic-conventional dichotomy and emphasize that, in order to optimize environmental sustainability, individual tactics must be evaluated for their environmental impact in the context of an integrated approach, and that policy decisions must be based on empirical data and objective risk-benefit analysis, not arbitrary classifications.

The paper was Choosing Organic Pesticides over Synthetic Pesticides May Not Effectively Mitigate Environmental Risk in Soybeans (full text) by Christine Bahlai et al. Long story short, the research showed that some synthetic pesticides were more environmentally benign than some organic pesticides, showing that it’s inaccurate to say that organic pesticides are better for the environment. Sometimes they are, and sometimes they are not.

The paper itself is really great, deserving of its own post (see Organic pesticides aren’t necessarily more sustainable than synthetic by Colby Vorland), but I’d like to talk about the organic-conventional divide. Normally I don’t approve of thoughts in scientific journal articles that aren’t immediately related to the research, too often authors stray into questionable territory. But Christine’s thoughts here are immediately related to her findings, and her results may indicate that big changes are necessary in the way we think about farming.

Separating out “organic” as defined by the USDA may be beneficial in the short term for farmers that have transitioned to certified organic methods who can then charge a premium, but in the long term, the divide is a detriment to farmers, consumers, and the environment. If we really care about farming in a more environmentally friendly fashion, we need an entirely new system.

We all want the same things*:

1. healthy food that is accessible to everyone regardless of location or income
2. farmers that can afford to farm and to pay fair wages to their employees
3. conservation of resources (especially soil!) and protection of ecosystems

We can get those things through three complimentary and often intertwined avenues:

1. demand
2. policy
3. research

Demand driven change seems to be moving along. We see lots about healthy food in popular media, increasing popularity of farmers’ markets, talk of adding cooking classes to public schools, and a push to make school lunches healthier, just to name a few. More could be done, but it is happening. We might have different ideas of what exactly constitutes healthy food, but I don’t think anyone’s arguing that more fruits and veggies is a bad idea. Ok, probably someone is, but let’s just agree to ignore them.

Policy driven change seems to be moving along as well. Michelle Obama is leading the charge with her Let’s Move program that touches many government programs. Kathleen Merrigan is pushing for help for local food systems, even while Tom Vilsack works mostly within the status quo. As demand for healthier food increases, senators and congressmen will be more likely to support policy changes at the federal level, especially if we somehow start electing people with backgrounds other than business. Yes, it would be nice if everything changed faster, but it’s going to take a while to change a system that’s been in place for 40+ years.

With both demand and policy, the important thing is to keep pushing for changes, and over time things will change. Optimistic, simplistic, yes, but true. The alternative is revolution, which would probably suit some people, but is more than a little extreme.

That leaves us with research. Research is what informs both demand and policy – or at least it should be. Research can provide us with information about which methods are preferable to others, such as which pesticides would have the least impact on farm and off farm ecosystems. Research, if properly applied, can help guide demand and policy to improve human and environmental health, among other things.

Here’s the problem, to borrow from the pesticide comparison paper: not enough “empirical data and objective risk-benefit analysis” and too much “arbitrary classification”. When demand and policy are based on arbitrary classifications like “natural is better” without research to back it up, we end up with demand and policy that are ineffective at best. We also end up with unnecessary divisions that cause efforts to be split, even though we all really want the same thing.

Let’s look at organics as defined by the USDA:

…an ecological production management system that promotes and enhances biodiversity, biological cycles and soil biological activity… The primary goal of organic agriculture is to optimize the health and productivity of interdependent communities of soil life, plants, animals and people. (USDA National Organic Standards Board definition, April 1995)

or agriculture that does

…respond to site-specific conditions by integrating cultural, biological, and mechanical practices that foster cycling of resources, promote ecological balance, and conserve biodiversity. (CFR Regulatory Text, 7 CFR Part 205, Subpart A — Definitions. § 205.2)

Sounds great, right? Except that by separating organic out from the rest of agriculture, we’re implying two things:

1. that non-organic-certified farmers don’t have these goals in mind
2. that they don’t have to.

It probably is true that some conventional** farmers don’t care about their soil, don’t conserve resources, etc. But those aren’t going to be very sucessful farmers if their soil is poor and they have to buy way more fertilizer than their neighbors, for example. If you lined up all of the farmers in the US according to their soil quality, I bet you’d find a bell curve. In each category from bad to great soil, you’d find some conventional and some organic farmers. According to the research, organic methods can be better for soils than conventional methods***, but there is so much variation in how farmers actually apply the methods that a one farm to one farm comparison really doesn’t tell the whole story.

There are many conventional farmers that apply integrated pest management, that use rotations to reduce crop-specific pests, that use legume rotations to help reduce the amount of nitrogen that needs to be applied, that use planting methods that decrease soil compaction, and so on. And there are organic farmers that just do the minimum to keep certified. And a whole range between.

Even if we assume that, on average, organically farmed soils are superior in organic matter, microbial activity, etc, we’re still not saying much. “Certified organic cropland and pasture accounted for about 0.6 percent of U.S. total farmland in 2008″, according to the USDA. When we make regulations for such a very small portion of farms, we’re not actually doing anything at all. Consumers should demand environmentally friendly methods from the other 99.4% of farms and policy should be made that includes all of those farms – and all of it needs to be based on sound research.

Ideally, demand and policy would be based on those methods that have been shown to work. If additional research confirmed that using mineral oil was more harmful to farm ecosystems than one or more synthetic pesticides, then one would hope to see demand and policy encourage use of the insect control strategy that had the least impact instead of arbitrarily choosing the “natural” method over a synthetic. Right now, there’s little if any research driving demand or policy. Instead, we have ideology.

Infighting over whether organic or not-organic is better, can feed the world, blah blah blah, isn’t actually helping anyone. The reality is that some methods used by some organic farmers are superb and some might not be. Some should be widely adopted, and some might even be more harmful their conventional counterparts (see the study I started this post with). Complicate that with the fact that not all farmers use the same methods and trying to decide whether organic is better becomes completely futile.

The research looks at individual methods, not arbitrary classifications – which is  really the only effective way to look at things. What we really need is a system that rewards farmers for environmentally friendly farming practices****. A farmer that uses legume rotations for nitrogen but still needs to use some synthetic N, P, and K  to maintain good soil nutrients should be rewarded or recognized somehow if he uses application methods that have been shown to reduce runoff. A farmer that uses integrated pest management to reduce chemical pesticide application that farmer should be recognized.

Hypothetical label touting E-value of contents.

Perhaps there could be a scoring system where environmentally friendly methods are given a number value and farmers with higher values can seek a higher price from buyers that are interested in such things. I can easily imagine a box of corn flakes labeled “made from corn with E-values of 100 or higher!” Another option might be to revamp the whole subsidy system to focus on farming practices, where farmers could have a financial incentive to choose environmentally friendly practices, epecially in cases where a change from one method to another would have an initial capital cost (like new tilling equipment) or when the change might reduce yields or income.
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Let’s put aside the petty squabbling and focus on the research that has the potential to guide 100% of farms toward more sustainable methods. Not enough research? Let’s demand better federal funding for relevant projects. Let’s demand policy that helps all farmers and all land, not just some.

So, farmers organic and conventional, advocates of various farming methods, consumers, economists, policy analysts, everyone… What sorts of incentive systems might work? Would you spend a little more for a product that you knew was made with ingredients that were sustainable grown? Would this whole crazy idea be just too expensive to implement? Would the cost be mitigated by the benefits?

Bahlai CA, Xue Y, McCreary CM, Schaafsma AW, & Hallett RH (2010). Choosing organic pesticides over synthetic pesticides may not effectively mitigate environmental risk in soybeans. PloS one, 5 (6) PMID: 20582315

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* Yes, agribusiness wants something else – money. But I’m talking about people, not corporations here. And if you think organic agribusiness cares any less about money than other companies, you are simply naive.

** I really don’t like the word conventional, but it’s better than saying “non-organic-certified” every time I want to mention farmers that aren’t organic certified.

*** To name one recent study that shows healthier soil under organic methods:  Moeskops B, et al. 2010. Soil microbial communities and activities under intensive organic and conventional vegetable farming in West Java, Indonesia. Applied soil ecology 45(2)112-120. Within the confines of this particular study, organic soils are closer to local forest soils, but I bet there are farms which would show the opposite to be true. As with all studies, we have to be careful to remember that the findings apply within the conditions of the study and may or may not apply elsewhere.

****I’m not advocating a dissolution of the certified organic system. It’s not perfect, but it’s all we’ve got at the moment. I’m just saying we can have a system that actually works to improve all farms, and organic can keep doing whatever its adherents want.

The various methods of generating electricity are a great example. Humans have become dependent on energy for so many things, some frivolous and some necessary (depending on your point of view). Unless we are all willing to forego electricity, we must find some way to power our lives. Current methods, including coal, have harmful unintended consequences that many of us would say outweigh the positives that we get from the electricity that is generated. Water power, once thought to be one of the cleanest methods of generating electricity, has been found to cause problems big and small. Nuclear has its own set of problems, as does wind.

Because each solution has positive and negative effects, the best we can do is examine each situation individually using the best science available and decide how to achieve the most positive effects while decreasing the negatives. Plant genetics is no different from power generation in this respect.

Every individual plant trait obtained with biotechnology, mutagensis, wide crosses, etc has its own set of positives and negatives. This means that sometimes a biotech solution will work well, sometimes a low-tech traditional solution is best, sometimes the necessary solution is totally out of the box. It makes no sense at all to be “pro-GMO” or “anti-hybrid” or anything like that because those stances don’t take into account the intricacies of individual situations. There might be times when using a hybrid is a bad idea and times when using a GMO is a good idea, but there will also be times when the opposite cases are true!

To complicate things further, plant traits can’t just be considered on their own merit. There will usually also be a complex set of factors including psychology in the form of tradition, fears, education, and so on. There’s economic factors from the individual level all the way up to local, national, and global levels. There’s environmental factors of course, since any agricultural methods can have an effect on ecosystems near and far. And that’s just a few of the many factors that might be involved. We also have to consider what our goals are and how they fit into the big picture.

Considering all of these factors isn’t easy, which I think is a big part of why some people like to sum things up and be anti this or pro that. Easy isn’t always right, though.

How about you? Are you pro-GMO? Anti-GMO? How about pro- or anti-mutagenesis or tissue culture or any of the other techniques out there? Does it make more sense to be pro- or anti- a specific technology or method or to consider an application of that method?

Below you can find my results with a through explanation of what I’ve done and why. The results are posted without all the commentary at Produce Pesticide Rankings which has all of the results and Pesticide Produce Rankings Tables which has comparisons of my results to the EWG results. You can download the original USDA data yourself or check out the Latest PDP Findings of Interest to Consumers.

See Produce Pesticide Rankings Part 2 for the real scoop on which produce is the most and least safe.

Concentration and LOD

My first step was to compare the detected Concentration to the Limit of Detection. The LOD seems to have been ignored by EWG. The LOD is the smallest concentration of the chemical you are looking for that will give a positive signal with the method used. Every method/chemical combination has a different LOD that can be found by comparing a blank (no chemical) to smaller and smaller concentrations of the chemical. If the detected concentration is at or below the limit of detection, it does not indicate the chemical is present – which is not the same as saying the chemical is not present. The chemical could be there, but the amount is so small that it can not be detected with the method being used.

Let’s put some numbers on it. There were 1,780,365 tests conducted on 13,381 samples (including fruits, vegetables, fish, nuts, and water), with 33,426 of those tests having a concentration listed (1.88%). Of those, 273 were equal to the LOD leaving 33,153 positive concentrations (1.86%). Not a big difference, but still, it would be incorrect to include the concentrations that are below the LOD. In a lot of experiments a blank is subtracted from the results and I can’t think of a reason why that wouldn’t be appropriate here. So, I created a column of Concentration minus LOD and used these numbers for my calculations.

One drop of water is 2 ppm of a bathtub full of water. Image from the Alaska Department of Environmental Conservation.

Units

Most of the tests have a unit of ppm (parts per million), but some are ppb (parts per billion) or ppt (parts per thousand). I converted ppb to ppm (ppb/1000=ppm) and ppt to ppm (ppt*1000=ppm) so all of the average residue values would be in the correct units.

It would be inappropriate to average values with different units. As illustrated by the Alaska Department of Environmental Conservation, ppm is drops per bathtub while ppb is drops per swimming pool!

Comparing the 2008 data with EWG

Because this investigation was inspired by EWG, let’s go through their Spreadsheet column by column to compare the top five values of each. You can find this information in Pesticide Produce Rankings Tables. The 3 types of water tested by USDA top most of the lists in the 2008 data, but since this discussion is on produce, they aren’t included here.

Percent of samples tested with detectable pesticides

This isn’t really a good metric because it doesn’t take into account which of the detected residues are above or below the EPA tolerance level and the EWG numbers don’t take the LOD into account (the numbers I report are all Concentration – LOD), but nonetheless here’s how they stack up.

• % of samples with 1 or more residues: 95.78 Peaches, 95.55 Celery, 95.24 Nectarines, 94.06 Strawberries, 92.75 Catfish.
• % of samples with 2 or more residues: 89.74 Celery, 88.66 Strawberries, 86.04 Peaches, 80.65 Nectarines, 72.22 Blueberries.
• EWG % of samples tested with detectable pesticides:  97.20 Plums, 96.20 Peaches, 95.10 Bell Peppers, 95.00 Celery, 93.60 Apples.
• EWG % of samples with two or more pesticides: 85.70 Peaches, 84.70 Celery, 82.30 Blueberries, 80.60 Bell Peppers, 74.40 Apples.

As you can see, the percentages don’t vary much from the collection of data used by EWG to the 2008 only data. Some of the foods tested in previous years weren’t tested in 2008 (apples, bell peppers).

A lot of the samples for each commodity have 1 residue, fewer have 2, fewer have 3, and so on. For some perspective, consider the percentage of all tests done on all samples for each commodity that had one or more residue.

• % of tests with 1 or more residues: 1.18 Nectarines, 0.92 Collard Greens, 0.90 Summer Squash, 0.83 Kale, 0.79 Almonds.

Average number of pesticides found on a single sample

This is a little more useful than the percent of samples with one or more residues, but not by much, since we’re still leaving out consideration of the EPA tolerance.

• Mean residues detected per sample: 5.15 Celery, 4.94 Strawberries, 3.61 Blueberries, 3.50 Peaches, 2.46 Spinach.
• EWG Average number of pesticides found on a single sample: 3.79 Celery, 3.08 Peaches, 3.00 Blueberries, 2.90 Strawberries, 2.75 Apples.

The USDA lets us know in their Latest PDP Findings of Interest to Consumers that the number of samples with pesticides and number of pesticides per sample doesn’t correlate to pesticides per serving size because the sample sizes were a lot more than a serving. “Sample size ranges from 16 ounces to 5 pounds depending on food tested. For example, for peaches and celery, the sample size is 5 pounds; for strawberries and blueberries is 3 pounds and 1 pound respectively.”

In regards to number of pesticides per sample, the USDA states: “There may be many more pesticides available for use by food producers, but 20 years of testing show that no food has ever been treated with all available pesticides.”

Average amount of pesticides found in ppm

This might be the worst metric of all because it averages pesticides that have very different toxicity levels. One ppm of one pesticide can be very different from one ppm of another pesticide! Still, here’s where we start to see some real differences!

• Mean ppm residue by commodity: 0.8 Potatoes, 0.61 Spinach, 0.37 Rice, 0.35 Nectarines, 0.33 Sweet Potatoes.
• EWG Average ppm of all pesticides found: 1.602 Potatoes, 1.373 Spinach, 1.200 Plums, 1.066 Peaches, 0.906 Red Raspberries.

The EWG shows average ppm of pesticides that are twice what I’ve got from the 2008 data! What’s happening here? One possibility is that EWG didn’t convert the ppt to ppm, but surely they’d notice the different units in the data, so it must be something else. We could have done the averages differently, but that’s unlikely too, it’s just averaging.

The only other thing I can think of is that there were high levels of residues in the past, high enough to skew the overall averages. If this is true, then we have something to celebrate – there have been great reductions in pesticide residues over the years!

Still, this brings up a question: why would the EWG tell people that produce has such high amounts of pesticide residues when produce today actually has much less? If the goal is to tell people what are the safest foods to buy for their families today, why include old data?

The USDA states specifically in their Latest PDP Findings of Interest to Consumers that there have been significant changes over the years, with reduced number of samples with pesticides and reduced ppm of pesticides. Specifically, there have been reductions in the most harmful pesticides as safer alternatives have been approved for use.

Maximum number of pesticides found on a single sample

Again, this metric does not take the EPA tolerances into consideration, and the results are about the same..

• Maximum residues detected per sample: 14 each Strawberries and Celery, 12 Blueberries, 11 Catfish, 10 each Spinach, Collard Greens, and Peaches.
• EWG Maximum number of pesticides found on a single sample: 13 each Blueberries, Strawberries, and Celery, 11 Bell Peppers, and 10 Kale.

Considering the EPA tolerance levels

Now that we have those comparisons out of the way, let’s look at the pesticide residues that the USDA finds to be of concern: Pesticide Produce Rankings Part 2.

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*Thanks to my husband for explaining that it makes a lot more sense to keep the test data and the sample data in two separate tables that you join when needed based on the sample number. Having all the data in one JMP file is about 8mB which doesn’t work all that well even on a good computer.

EWG gives many many reasons why they think you should use the guide, specifying that you (the consumer) should eat organic or at least choose the Clean 15™ over the  Dirty Dozen™:

The 12 most contaminated fruits and vegetables (the “Dirty Dozen”) are contaminated with an average of 10 different pesticides, with many tainting more than one type of produce. In contrast, the “Clean 15,” the 15 least contaminated fruits and vegetables, contain an average of less than 2. Eating organic food lowers pesticide body burdens as well. Research shows that concentrations of pesticides in children’s bodies peak during seasons that they eat the most produce, but fall to below detectable levels in just 5 days when they eat organic food.

The list of reasons has a lot of scary facts about how many pesticides detected on food, just how “polluted” our bodies are from the things we eat, and explains how our government barely regulates pesticides. Near the bottom, EWG lets us know that despite the scary facts that the need to eat fresh produce outweighs any risk from pesticide residues. They also remind consumers of the importance of eating fresh produce on their FAQ page. Unfortunately, I’m not sure if anyone gets to that part, considering that media coverage of the Shopper’s Guide rarely mentions it, instead focusing on the scary facts (as in ‘Dirty dozen’ produce carries more pesticide residue, group says on CNN Health, which dismisses the silly government for thinking that small amounts of pesticides won’t hurt us).

The truth is, pesticides are scary. As EWG’s Amy Rosenthal says, “Pesticides are designed to kill things.”

The devil, as always, is in the details.

We need the EWG

Before we get into those details, I’d like to say a few things about the Environmental Working Group in general, or really any group that does what EWG tries to do. EWG has the ability to provide a very important benefit to society. Government spending on science has decreased over the years, leaving most toxicity research to the companies that make the products being tested. Until we follow the wise leadership of India and develop a network of government certified independent testing labs, we’re all kind of left with less information than I’d prefer for many products we use every day. It’s not that I think every corporation is driven by people who choose profits over safety (on the contrary, they have to at least think their products are safe or suffer bad press or worse if people get sick) but results of corporate funded tests are often not made available to the public which leaves regulators with less info than they need to make good science-based decisions. Our system works fairly well (the grand majority of people get through life without health problems caused by things they can’t control other than their own genetics*) but it could always be better. EWG works to get information to regulators and presents a non-industry point of view, which is much needed. Unfortunately, despite their outwardly awesome intentions, some of the results are less than awesome.

Details, details

Danger, elephants. Taken by Adam Foster at Knowsley Safari Park in England. via Flickr.

In the materials accompanying the Shopper’s Guide, there are two details that are never discussed.

The first elephant in the room is dose. For any compound, from water to arsenic to ricin to organophosphates, there are amounts that are safe and amounts that are hazardous. There are amounts that will cause acute (immediate) reactions and amounts that will cause chronic problems after long term exposure. Are the amounts of pesticides found on produce enough to cause acute or chronic health problems? The EWG list does consider amount, but does not compare the amounts to EPA guidelines. The accompanying materials focus on the number of pesticides, not the dose.

The second elephant is the type of pesticides that were found on produce. There isn’t any weighting in the Shopper’s Guide of individual pesticides based on relative toxicity. This could be a problem because not all pesticides are created equal. Organophosphates, for example, are extremely dangerous because they affect cholinesterase, an enzyme that is essential for the human nervous system. Glyphosate, on the other hand, affects EPSPS, an enzyme that is only found in plants so human toxicity is low (surfactants and other ingredients in glyphosate containing herbicides may be dangerous in their own right, but EWG to my knowledge isn’t talking about those types of ingredients).

Careful consideration of dose and toxicity of pesticides on produce may mean a reordering of the list is necessary in order to truly keep consumers safe. It may also mean that many of the scary facts need some sober facts alongside to help us keep things in perspective. Let’s look at the  methods that EWG used to make the list and at the original USDA data.

EWG’s Methods

I have to tip my hat to EWG for providing their methods on their website. I don’t know how many people look at it, but I certainly did! They provide justifications for not discussing dose or type of pesticide:

The goal is to include a range of different measures of pesticide contamination to account for uncertainties in the science. All categories were treated equally; for example, a pesticide linked to cancer is counted the same as a pesticide linked to brain and nervous system toxicity, and the likelihood of eating multiple pesticides on a single food is given the same weight as the amounts of the pesticide detected or the percent of the crop on which pesticides were found.

The problem is that, as strange as it may sound, there are safe amounts of pesticides. With the incredibly low detection limits that advanced methods provide us, we can expect many positive results that aren’t biologically significant. This is why the EPA bothers to determine tolerance limits for each pesticide (see below: The Data). The EWG continues:

The EWG’s Shopper’s Guide is not built on a complex assessment of pesticide risks but instead reflects the overall pesticide loads of common fruits and vegetables. This approach best captures the uncertainties of the risks of pesticide exposure and gives shoppers confidence that when they follow the guide they are buying foods with consistently lower overall levels of pesticide contamination.

In other words, science-based risk assessment is bad because it’s complex? A less complex and unscientific method gives consumers more confidence than a science-based method? Perhaps, but this explanation of the method is a little too close to fibbing for my taste. Maybe we need to look deeper.

EWG looked at contamination in 6 different ways:

• “Percent of samples tested with detectable pesticides.” Assuming that the data was used properly, this is a good metric. It tells us how many of all the samples within a category had pesticide residues.
• “Percent of samples with two or more pesticides.” This metric might be useful if we are concerned about potential effects of consuming more than one pesticide.
• “Average number of pesticides found on a single sample.” This isn’t as useful as a median number of pesticides could be. If most of the samples contain 0 pesticides, the average would be lower than the median. If only one of the samples contains a very large number of pesticides, the average would be artificially high.
• “Average amount (level in parts per million) of all pesticides found.” Here’s where the science gets thrown out. The type of pesticide isn’t considered even though we know that some pesticides are dangerous at low doses while other pesticides are safe at much higher doses. The ppm of different pesticides should not be averaged unless they have similar toxic doses. No where on the Shopper’s Guide site  is there a discussion of how the pesticide levels found in produce match up to EPA guidelines, or how those guidelines are created (in most cases the guidelines from the EPA are at least 10 times lower than the actual dangerous dose).
• “Maximum number of pesticides found on a single sample.” This isn’t very useful either. Perhaps one sample was grown by a particularly zealous farmer who used more pesticides than she should. Perhaps the single sample was accidentally contaminated. Should the entire category of produce be condemned because of this single sample, out of hundreds of samples? Using the median number of pesticides for all of the samples make much more sense.
• “Total number of pesticides found on the commodity.” Again, this number could be based on one or a few samples which are not representative of all of the samples.

The Data

High speed capture of dye droplets by Derek Purdy. via Flickr.

Since 1991, the Agricultural Marketing Service (part of the USDA) has collected data on pesticide residues in food as part of the Pesticide Data Program (PDP) using pretty rigorous methods (pdf). In addition to this testing, the FDA tests domestic and imported food to ensure that pesticide residues are below the tolerance levels (FDA probably doesn’t test enough samples due to funding cuts but that’s another post). The results are compared to tolerance levels (maximum pesticide residue limits) that are set by the EPA (you can find the tolerance for each crop/pesticide/country combo at Maximum Residue Levels database). According to the Latest PDP Findings of Interest to Consumers (pdf), ”the vast majority of samples tested are well below the tolerance levels”. Specifically:

The USDA provides some comparisons to help us understand what 1 part per million is: 1 ounce of salt in a mountain of 62,500 pounds of sugar or 1 ounce of dye in 7,350 gallons of water.

The most recent Annual Summary of the PDP (pdf) contains data that was collected in 2008 and was released in December 2009. The Executive Summary tells us that 11,960 samples were analyzed, including fresh and processed fruit and vegetables (9,028 and 1,354 samples respectively), almonds, honey, corn, and rice (municipal drinking water is also tested). The positive pesticide residue detections were combined by food type; on average 1.6% of samples had positive residue detections. For fresh produce, positive samples ranged from 0 to 3.3% with an average of 1.9%. They go on to say:

For samples containing residues, the vast majority of the detections were well below established tolerances and/or action levels. Before allowing the use of a pesticide on food crops, EPA sets a tolerance, or maximum residue limit, which is the amount of pesticide residue allowed to remain in or on each treated food commodity. Established tolerances are listed in the Code of Federal Regulations, Title 40, Part 180. In setting the tolerance, EPA must make a safety nding that the pesticide can be used with “reasonable certainty of no harm” and that residues at (or below) the tolerance are safe. The reporting of residues present at levels below the established tolerance serves to ensure and verify the safety of the Nation’s food supply.

To restate, the methods used to detect pesticides are very sensitive, but a positive sample does not indicate a problem unless the detected level is above the established tolerance level. “A tolerance violation occurs when a residue is found that exceeds the tolerance level or when a residue is found for which there is no established tolerance.”

There were 60 samples that exceeded tolerance levels, making up 0.5% of all the samples (58 with 1 residue exceeding the tolerance and 2 with 2). There were 442 samples that had pesticide residues that don’t have established tolerance levels, making up 3.7% of all the samples (one reason why there isn’t an established tolerance level is that the pesticide in question isn’t labeled for use on the specific crop being tested). “In most cases, these residues were detected at very low levels and some residues may have resulted from spray drift or crop rotations.” Starting on page 51 of 202, the results are presented in a table the includes the number of samples tested, the number of positive samples by pesticide type, the amount of pesticide detected, and the EPA tolerance for that pesticide. I encourage you to see the report for all the details. The actual data can be downloaded from the Agriculture Marketing Service, although sadly it isn’t in any sort of convenient format (I’m wrestling with the data right now).

Peaches

There do seem to be some discrepancies between what EWG says the USDA data says and what the USDA data says.

The EWG says “more than 96 percent of peaches tested positive for pesticides”, and “peaches had been treated with more pesticides than any other produce, registering combinations of up to 67 different chemicals.” That sounds pretty bad.

Table 3 of the 2008 USDA report lists the “Number of Samples Analyzed and Summary of Results per Commodity” (page 34). According to this table, 616 peach samples were analyzed, with an average number of 130 different analyses conducted on each individual sample, resulting in a total of 80,184 tests done on the 616 peach samples. Of these tests, 2,155 were positive for pesticide residues, and 52 different pesticides were detected. While the number of positive detections out of all the tests isn’t the same as the number of positive samples out of all the samples, it is still interesting to know that only 2.7% of all the tests conducted on peaches were positive.

52 isn’t 67. 2.7% isn’t 96%. What’s happening here?

EWG didn’t use the most recent data. Instead, they seem to have combined data from 2000 to 2008. That seems very strange to me, considering that EPA regulations for allowed pesticide use and allowed pesticide tolerances have been changing over the years, becoming more strict. At least they didn’t include pre-2000 data, but still this isn’t the best way to find the information that consumers want. We need to know how many fruits and vegetables today are positive for pesticides, not all the fruits and vegetables in the past decade.

Even when we consider the fact that the EWG isn’t working with the best dataset, that still doesn’t answer how they decided that more than 96% of peaches were positive for pesticides. Hopefully the answer will be clear once I’ve looked at the USDA data myself.

If not scary “facts”, then what?

I am definitely an advocate of using science-based approaches to farming that reduce input use overall, and of careful Integrated Pest Management strategies that use the safest possible solutions to any pest problem, only using inputs if other options have been unsuccessful, and using the safest possible pesticide whether that pesticide is natural or synthetic.

How do we encourage government to introduce regulation that will make this happen and how do we encourage consumers to care about this enough to talk to their elected officials?

The best course of action would be to present the information in a less agenda driven way. Provide the data along with the EPA guidelines, which would show that the great majority of produce is well within guidelines. There are ways to advocate for reduced pesticide use without alarming people unnecessarily.

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* In the developed world, health problems caused by our own choices (bad nutrition, lack of exercise, smoking, and so on) dwarfs any problems that might be caused by normal use of household chemicals, plastics, foods, etc.

Note: A group called Alliance for Food and Farming, called an “industry front group” by EWG has challenged the Shopper’s Guide, saying that it unnecessarily alarms consumers. I have not read any materials from AFF on this subject prior to writing this post to be sure that my comments were not based even subconsciously on their comments. I heard about the AFF response through the Iowa State Sustainable Agriculture Listserv, which led me to write a few responses about the Shopper’s Guide to the original poster which then were turned into this post. This year’s Shopper’s Guide came out in June 2010.

Bt effectively and selectively kills certain insects. Images from the Bacillus thuringiensis info page.

Bt, short for Bacillus thuringiensis, is a bacteria that produces a protein that kills certain types of insects. Different types of the gene that produces thais protein have been engineered into crops to make them resistant to those insects. The approach has been quite successful but the details can be confusing.

If you’re looking for science-based information on Bt crops, check out the Bacillus thuringiensis info page that was developed by Karen Chien of the University of California, San Diego, with the assistance of Raffi Aroian. The material is a little dated, but it’s still a great resource. I especially enjoy the cartoons!  :)

The Aroian lab studies the ways that “target pests develop resistance to Bacillus thuringiensis crystal proteins in order to protect this valuable natural resource.” They’re also studying how Bt could be used to treat parasites in animals and people, as in their recent article in PLoS: Bacillus thuringiensis Cry5B protein is highly efficacious as a single-dose therapy against an intestinal roundworm infection in mice (full text).

Thanks to Mica Veihman (@Mica_MON on Twitter) for reminding me about this great resource.

An Arabidopsis stomate showing two guard cells exhibiting green fluorescent protein and native chloroplast (red) fluorescence. via Wikipedia.

This image is an extreme closeup of a stomate (singular, the plural form is stomata). These two cells, called guard cells, control the plant’s respiration: how much carbon dioxide gets in and how much oxygen and water vapor gets out. The control isn’t very good, though. Most plants just have their stomata open all day every day so they can pull in lots of CO2 to use during photosynthesis to make sugar. And that means a lot of water, painstakingly pulled up from the soil, through the roots, gets lost. If stomata could be more selective, only opening when more CO2 was needed for photosynthesis, then water could be conserved.

An enzyme called carbonic anhydrase raises the levels of CO2 in chloroplasts so the plant can make plenty of sugar. It does this by converting CO2 from its storage form carbonic acid back to it’s useable form: CO2 + H2O ⇌ H2CO3.

Carbonic anhydrase also appears in the guard cells, where it controls the opening and closing of stomata.

Julian Schroeder, Professor of Biology at UC, San Diego hypothesized that more carbonic anhydrase in the guard cells would place tighter control over opening and closing. His group tried shutting off the carbonic anhydrase gene in the stomata of a little plant called Arabidopsis. Those plants were unable to respond to increased CO2 concentrations in the air, remaining open all day. They also tried expressing additional copies of the carbonic anhydrase gene in the stomata. Those plants closed their stomata when water was scarce. This makes sense – carbonic anhdrase needs water to function, so it can’t function when water’s not around.

Honghong Hu, a postdoctoral research working on the project, said in the press release Newly Identified Enzymes Help Plants Sense and Respond to Elevated Carbon Dioxide and Could Lead to Water-wise Crops: “The guard cells respond to CO2 more vigorously. For every molecule of CO2 they take in, they lose 44 percent less water.”

This research, Carbonic anhydrases are upstream regulators of CO2-controlled stomatal movements in guard cells, published in January 2010, indicates that increasing the number of carbonic anhydrase genes in the stomata could potentially decrease the water lost through stomata in crops. The implications for drought prone regions are obvious. Plants could need less water and could hold on to the water they have longer. It won’t be plug and play, though. As stated in the press release, water that evaporates from stomata cools the plants just like water evaporating from our pores cools us. Increased expression of carbonic anhydrase will have to be tested to determine its effects on plants in high temperature environments.

Hu H, Boisson-Dernier A, Israelsson-Nordström M, Böhmer M, Xue S, Ries A, Godoski J, Kuhn JM, & Schroeder JI (2010). Carbonic anhydrases are upstream regulators of CO2-controlled stomatal movements in guard cells. Nature cell biology, 12 (1) PMID: 20010812

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Thanks to @RivenCactus for bringing this research to my attention by Tweeting a link to the TreeHugger article Newly Discovered Enzyme Could Create Crops That Thrive in Dry, High CO2 Conditions.

If a gene like this was used to make crops more drought tolerant, could it spread to weeds and make weeds weedier?

Yes and no.

If there was a sexually compatible wild relative or weed species growing nearby the drought tolerant crop, it is possible that weed/crop hybrids could include the gene. Sexual compatibility means that the weed not only has to be a fairly close relative to the crop but also means that they have to be pollinated by the same method, have pollen shed at the same time, not have any incompatibility genes, etc. In the United States, there are few weed species that are sexually compatible with crop species, but there are some. In these cases, farmers can use the same sort of strategies to reduce gene flow that they would use to avoid spread of a conventionally bred trait.

If gene flow does happen, the gene will only be present in the weed population at low levels, unless the gene makes the weeds that have it able to outcompete weeds that don’t have it. See Escape! Crop-Specific Gene Flow to Wild Relatives and Those naughty plants! on Biofortified for more discussion of gene flow.