Rise of the Superweeds

One of the arguments against GMOs has been that they caused the evolution of so-called “superweeds”, an epidemic that apparently has the world headed for a crisis. Some claim that we will soon be unable to sustain our modern agriculture techniques, and GMOs are at fault.

Fortunately, the reality is quite different. Superweeds are indeed a problem, and their evolution is causing significant problems for farmers. However, we do have options to control them, and emerging technology is going to help us out.

Superweeds – What Are They?

Superweeds really aren’t that super. They aren’t bigger, faster growing, or more competitive than “normal” weeds. All a superweed actually is is a weed that is resistant to a certain type of control. Becoming resistant to Roundup (glyphosate) doesn’t automatically make a weed more competitive, it just makes it more difficult for us to control them. It eliminates one of the tools we have in our toolbox.

palmer-amaranth
Palmer amaranth is one of the most prolific glyphosate resistant weeds in the US, producing up to a million seeds per plant. (Superior Ag Resources photo/Tom Sinnot)

A common misconception is that superweeds are only resistant to glyphosate, but that is actually not accurate. Weeds have been evolving resistance to many kinds of control for as long as agriculture has been around. In fact, in India, farmers used to hand weed barnyard grass out of rice. Barnyard grass was very similar in appearance to rice, but it had a distinctive red stem. As farmers removed those weeds year after year, a different strain of barnyard grass with a green stem became more prevalent. Eventually, farmers could no longer tell the difference between barnyard grass and rice; they had selected for green stems (read more here). Essentially, you could call that particular strain of barnyard grass a superweed. 

What Causes Superweeds to Develop?

Like the example of the red-stemmed barnyard grass, evolution of resistance to glyphosate and other chemicals is really rather simple. Continuous application of the same chemistry to the same fields year after year will allow that one weed with natural resistance to proliferate. One year, there’s one of them. That weed produces dozens or – believe it or not – millions of offspring. In year two, depending on how many germinate, survive and reproduce, an exponential increase in resistant populations begins.

All that particular weed has is a mutation that allows it to survive the chemical. Lentil harvestSometimes, it can only survive a lower rate, which is why proper application rates are
so important. As that weed begins to spread, it finds its way into other fields and other farms. Combines do a great job of blasting weed seeds hundreds of feet through the air, and with the right wind, weed seeds can even be blown into adjacent fields.

Whose Fault Is It?

Are farmers to blame for this? In a word, yes. We are responsible for understanding the chemicals we apply on our own fields. Don’t get me wrong; I’m not trying to throw myself and my colleagues under a bus here. But there have been many farmers that simply grew Roundup Ready crops over and over for over a decade – applying incredible selection pressure to their weeds. Could pesticide companies do more to educate farmers on this subject? Yes, but they have vastly improved their education efforts. A fantastic example is Bayer Crop Science’s Mix It Up campaign, which informs farmers how their products can improve resistance management (read more here). I think the key going forward is that assigning blame gets us nowhere. Let’s instead focus on solutions.

When Roundup was first released, it was a novel herbicide that was considered to have “Low” susceptibility to resistance. Because of its mode of action, weeds would have to develop a complex resistance mechanism. Sadly, this assumption led to an overapplication of glyphosate, much of it at rates too low to be totally effective, and has thereby resulted in the loss of one of the great inventions of the modern age to many regions.

How Do GMOs Fit In?

The introduction of Roundup Ready crops in the 1990’s caused a surge in the use of glyphosate. It was cheap, safe, very effective on weeds and easy to apply. Despite what has been coming out in the media about glyphosate lately (read more here), it is actually a very safe product with no known health effects in humans or animals. It was a breakthrough in agriculture, one of the greatest of our time. It is because of this that its overuse was simply inevitable.

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A young GM canola crop with developing weed competition.

It is, however, important to distinguish that although Roundup Ready crops contributed to the overuse of glyphosate, they did not cause resistance themselves. Glyphosate is not the only product with resistance problems. Other chemical groups also have issues, such as sulfonylureas, imidazolinones, PPO inhibitors, plant growth regulators and so on have all led to the proliferation of their own resistant weeds. None of these products are tied to glyphosate resistant crops. In fact, even insects and plant diseases have evolved pesticide resistance. In Europe, for example, flea beetles have become resistant to pyrethroid insecticides. Canada thistle became a problem in the prairies largely because of cultivation, which allowed their roots to be spread all over the fields.

Any type of pest control can and will cause pest resistance if the selection pressure is high enough. Unfortunately for RR crops in the United States, the selection pressure was simply too high.

What Are We Doing About It?

Every problem has a solution, and superweeds are no different. The way to fix this problem is actually pretty simple – rotation. Using a variety of crops combined with a variety of chemicals prevents weeds from building resistance. Take that Roundup-resistant weed and hit it with something else. Maybe a different chemical, maybe a little bit of strategic tillage, maybe even just a more competitive crop.

There are some incredibly exciting developments in the world of crop protection. RNA interference technology may just be the new frontier in weed management. Palmer amaranth, a particularly problematic weed in the US, resists glyphosate by producing extra copies of EPSPS, an enzyme required for amino acid synthesis that glyphosate binds to and prevents growth, eventually causing death. It overcomes the glyphosate application by simply producing so many copies of EPSPS enzyme that it overwhelms the glyphosate molecules. To stop this from happening, RNAi prevents the production of the EPSPS enzyme. With less of it produced, glyphosate is once again effective (read more here and here).

While RNAi is very new and is probably years away from production, it is promising to see innovations like this on the horizon. In Australia, where weed resistance is a major problem, some farmers are using the Harrington Seed Destructor to destroy weeds as they leave the back of the combine, which is proving to be incredible effective. Robotic weed destroyers are prototypes today, but could be a game changer in the near future. But in the meantime, we must protect what we have. Careful rotations and proper application techniques will go far to secure the usefulness of the chemicals we have for the foreseeable future.

Superweeds are nothing new. Weeds always have and always will evolve survival mechanisms against our strategies to control them. GMOs are not the culprit here; a lack of discipline in the use of our most valuable chemistries is the reason we are having the problems we are having. Panic by local governments and knee-jerk reactions will not help us deal with weed resistance. Education, research and new ideas are what we need to combat this problem. Weeds have always been one of farmers’ greatest challenges, and we will have to continue to be innovative and determined to stay ahead of them.

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Why I Grow GMOs

What do you think about GMOs?

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Is there a more emotionally charged question out there in this part of today’s world? Certainly, it is understandable that the food we eat be an engaging issue for consumer and producer alike. There has been a drive from the consumer to learn about the food they eat. They want to know how it is produced, and whether it is in a sustainable fashion. Ultimately, and most importantly, they want to know if it is safe.  An unknown factor like genetic modification is a cause for concern for these people, because the long-term effects are not readily available to us.

I support and applaud those in the public that ask these critical questions. Too many people don’t think about the things that are done by the government, business and other organizations. The problem isn’t in people asking questions; it is in people asking the wrong questions to the wrong sources – and believing the answers without question.

I am a farmer that grows genetically modified (GM) crops. Not all of my crops are GMOs. In fact, in a usual rotation of 5-7 different crops, only two are GMOs. Canola and soybeans, two of my farm’s most economically important crops, are GMOs. Other crops, like wheat, peas and flax, are not GMOs, for there are simply none available. Contrary to popular belief, I do have a choice to buy GM crops or alternatives. So why do I grow GM crops when there are so many other cropping options?

That is a good question, and the answer will be different for every farm. In my life on the farm, canola and soybeans are our two newest crop options. In Western Canada, we have been growing wheat for as long as we’ve been farming. Flax and peas are old crops for us as well. Canola is one that we have really only been growing in earnest on our farm for the past 15 or so years. We only just started growing soybeans 3 years ago.

I suppose we could grow old open-pollinated canola and conventional soybeans (these are not GMOs). But would we do that? The claim I hear from some consumers is that GMOs are hazardous. By association then, I must be either cruel or naïve to grow these dangerous crops, putting other people at risk.

But here is the question I pose to the GMO haters: do you really believe I would grow these crops if I believed they were unsafe? My family eats the food we grow. I would not put them at risk if I truly believed GMOs were hazardous.

Honestly, I don’t believe they are. GM crops are not dangerous1. In the almost 20 years since Monsanto started genetically modifying corn, soybeans and canola, the evidence has become clear that the benefits of genetic modification far outweigh the risks1. This isn’t an opinion by a biased industry representative. The information I use comes directly from peer reviewed journal articles, the best source of information on anything scientific. GM crops also have dramatically reduced use of the most dangerous and volatile chemicals to control weeds2. Most of the GM plants we deal with are “Roundup Ready”, which means they are resistant to the active ingredient of Roundup, which is glyphosate. The way we measure the toxicity of chemicals like glyphosate is its LD50 number. This refers to the amount of the chemical, given all at once, which results in the death of 50% of the test animals3. The acute Low Acute Toxicity for oral consumption of glyphosate in rats is an LD50 value greater than 5,000 mg/kg of body weight4. This means that if you were a rat, and you weighed in at 3 kg, you would have to consume 15 grams of glyphosate for it to become toxic to you. That is quite a lot. Comparatively, the LD50 of caffeine is 192 mg/kg body weight. How much coffee do you have in a day? The point is, the dosage makes the poison, and any chemical can be toxic in a large enough dose.

Today’s farm operation is a complicated business. Every year, we run through the numbers on each crop to decide which ones to grow and on how many acres. Canola and soybeans, and especially canola, are profitable crop options for us. So yes, we do grow these GM crops because they allow our farm to make money. Are they making us rich? I wish! But they do allow our farm business to make enough money to survive, and hopefully, over time, prosper. Is this not the dream for us all?

Ultimately, the question of why I grow GMOs comes down to the fundamental freedom that we all have in our democratic society: the freedom of choice. It is my choice to grow GM crops. Conversely, if you don’t approve of them, it is your choice to buy something else. However, keep in mind the unintended consequences of doing so. GM crops allow us to use less toxic pesticides at lower rates. Furthermore, we can achieve unprecedented yields with the incredible biological advances made with these GM varieties. We need to grow 70% more food by 2050 to feed this growing world5; we are going to need all the tools we can get to accomplish this.

My farm grows GM crops, and I am proud to say that we do.  They are safe and sustainable crop options that we have the right to grow if we choose to. I hope that you will think about what I have said the next time someone asks you, “what do you think about GMOs?”

References:

  1. Stella G. Uzogara, 2000. The impact of genetic modification of human foods in the 21st century: A review. Biotechnology Advances 18 (2000): 179-206.
  2. RH. Phipps and J.R. Park, 2002. Environmental benefits of genetically modified crops: Global and European perspectives on their ability to reduce pesticide use. Journal of Animal and Feed Sciences, Vol. 11, pp. 1-18.
  3. United States Environmental Protection Agency, 2012. Lethal Dosage (LD50) Values. http://www.epa.gov/oecaagct/ag101/pestlethal.html
  4. Cornell University, 1994. Extension Toxicology Network. http://pmep.cce.cornell.edu/profiles/extoxnet/dienochlor-glyphosate/glyphosate-ext.html
  5. Agricultural Development Economics Division, 2009. High Level Expert Forum – How to Feed the World in 2050. http://www.fao.org/fileadmin/templates/wsfs/docs/Issues_papers/HLEF2050_Global_Agriculture.pdf