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Is Roundup the Next Big Threat to Our Food System?

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Roundup: The Next Big Threat to Our Food System?

Roundup, also known as GlyphosateEvery new technological fix in agriculture helps us forget a little more that it’s actually a living “thing” we’re dealing with. Kind of like an organism, a farm field lives and breathes and evolves. It’s a complex system that is quite biologically diverse and pretty capable of absorbing the next curveball we attempt to throw at it–just give it a few years.

Every new blanket approach also helps us forget a little more about the diverse weapons we once had at our disposal, often making us increasingly dependent on a handful of large-scale attacks. Glyphosate, generally sold under the name Roundup, has been a case in point. For over a decade after its 1996 release as part of the Roundup Ready genetically engineered crop and herbicide system, it seemed like a wonder drug for weeds, and began to supplant farmers’ once diverse but more toxic anti-weed arsenal. The Purdue University Extension Service gushed in a 2006 publication, “When applied postemergence to Roundup Ready soybean varieties and corn hybrids, glyphosate provides broad-spectrum, low-cost weed control with excellent crop safety. It is better than many other herbicides at controlling larger weeds, has no soil activity (allowing for flexible crop rotations), and has low environmental and human health risks.”

Beyond Pesticides, an anti-pesticide advocacy group, didn’t buy it. They wrote, “If there is one pesticide that represents the ‘fast-food,’ quick-fix generation, glyphosate would likely be it–the McPesticide of toxic chemicals…Glyphosate has replaced ecologically sound and sustainable cultural practices such as green mulching, and preventive maintenance such as aeration and dethatching.”

The one silver bullet to dwarf the weed problem seemed to have finally come along when in 1996 a glyphosate-resistant gene was successfully engineered into soybean seeds, followed by corn and cotton seeds, allowing Roundup to be sprayed indiscriminately with no damage to the crop.

Where farmers had once often had to use a cocktail of different herbicides with varying modes of action and a narrower range of target weeds, glyphosate could wipe out everything, providing a full season’s control for both broadleaves and grasses and leaving little environmental impact in its wake. “Glyphosate could make a bad farmer look good” when it came out on the market, said Robert Hartzler, professor of weed science at Iowa State University, since it left fields utterly weed-free, a feat few other herbicides could accomplish single-handedly.

Palmer Amaranth, also known as PigweedOverreliance quickly brought on the beginning of its downfall. Genes for glyphosate resistance were out there in the wild, floating within the weed gene pool, but ubiquitous glyphosate application made it all the more likely that natural selection would favor those genes where they happened to be expressed. Express themselves they did, and experts now count about ten resistant weed species, including giant and common ragweed, horseweed, Johnsongrass, waterhemp, and Palmer amaranth (also known as pigweed).

“Like the antibiotic-resistant bacteria that have infectious disease specialists fearing the worst, it is a problem we have brought on ourselves, a reminder of the futility of attempting to outrun evolution,” laments Scientific American.

Glyphosate looks irreplaceable, for the moment at least. No new herbicidal modes of action are currently being developed; the most recent mode of action to follow glyphosate’s 1970s debut was pigment inhibition, discovered in the 1980s. These developments are relatively rare, at least in comparison to plants’ abilities to evolve defenses. Glyphosate is now viewed as a once-in-a-century breakthrough.

Glyphosate resistance was almost unheard of before the release of Roundup and Roundup Ready crops, but then began to appear at a rate of about one species per year.

Almost any weed scientist would say that overreliance on one herbicide is a problem, since weeds will develop resistance without exception. It is just a question of when. The decline in glyphosate’s effectiveness is starting to signal a trend of returning to older, nastier herbicides, but weeds that have developed a glyphosate resistance are often difficult to control with other herbicides as well.

Weeds have had a largely consistent habitat to work with over the past 40-50 years, which has allowed for the selection of weeds that thrive easily in the corn-soybean rotation and under the regimen of dominantly-used herbicides. In the race for adaptability between us and them, they’ll probably take the long-term win. Life is almost always more diverse and resilient than the weapons humans invent to squelch it. And the best thing for many weeds is a predictable, controlled environment. We gave them just that in glyphosate and its exclusive application year after year.

With the eventual loss of glyphosate, farmers will again have to get used to walking their fields, observing their weeds and figuring out individual management strategies for each category. “Because of the raw profit margins, everything is designed to make it as simple as possible to cover as many acres as possible, by treating everything the same and minimizing the amount of time you spend in an individual field. We’re getting to the point where maybe that’s not going to hold up,” said Chemical and Engineering News. An important agronomic principle and a central tenet of organic agriculture, adding diversity and rotation to weed management is at the heart of what many extension agents advise. This extends to rotating between Roundup Ready and conventional crops or crops with other herbicide resistances, and not using more than two glyphosate applications on a field in a two-year period.

Some weed species are much more prone to develop a species-wide resistance to glyphosate, since the trait is spread to the next generation through pollen or seed. Weeds that are more prolific pollen and seed producers are quickly favored in natural selection against glyphosate. Contrary to common suspicions, however, the gene for resistance does not jump from the genetically modified crops to the weeds they compete with. Weeds native to the US are not similar enough to corn, cotton, and soybeans to breed with them.

One mechanism plants use to resist glyphosate is to quarantine the herbicide within the leaves, while the stem remains healthy. Interestingly, this is the same process that frequently happens with pathogen resistance, and researchers are keeping an eye on it for ideas for future pesticide developments.

Resistance means not only the need for more diversity in a farmer’s herbicide program, but it’s also meant more hoe crews out in the field to attack monster weeds. Pigweed, which can grow a stalk the width of a baseball bat, is capable of disabling a combine.

Glyphosate resistance probably could have been forestalled quite awhile if it had been used sparingly and in combination with other herbicides (but this would of course have added more expense and inconvenience to farmers’ lives). Medicine, too, takes a multiple-drug strategy to controlling fast-mutating pathogens, since an organism is not likely to spontaneously evolve resistance to several different chemicals at once.

Biotech companies are now working to engineer crops with genes for resistance to the more toxic herbicides dicamba and 2,4-D, but the lower safety ratings of these products make it harder to get them through the EPA registration process.

Scientific American remains doubtful that genetic engineering will offer the next solution on the weed management front. The two helpful and widely-used advances yielded by billions of dollars of research were, after all, glyphosate-resistant crops and Bt expression (a bacterial pesticide that has been genetically engineered into crops like corn). Conventional breeding techniques, on the other hand, got us insect and disease resistance, drought tolerance, and better yields. Maybe this old-fashioned, time-tested route that humans have taken practically since the beginning of plant and animal domestication will prove more useful than the next costly technological advance. The greater we distance ourselves from these methods, the more we forget about them – until that knowledge may no longer be close at hand as we grasp desperately to fill the void.

–Genevieve Slocum is a Contributor to The Free George.

The Free George is the online magazine and visitors’ guide of Upstate NY, covering things from Albany to Lake Placid, including Saratoga, the Lake George region and the Adirondacks. Check out our new City Blogs section for our extended coverage areas as well.

Short URL: http://thefreegeorge.com/thefreegeorge/?p=10569

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