Genetic engineering has failed to increase the yield of any food crop but has vastly increased the use of chemicals and the growth of “superweeds”, according to a report by 20 Indian, south-east Asian, African and Latin American food and conservation groups representing millions of people.
The so-called miracle crops, which were first sold in the US about 20 years ago and which are now grown in 29 countries on about 1.5bn hectares (3.7bn acres) of land, have been billed as potential solutions to food crises, climate change and soil erosion, but the assessment finds that they have not lived up to their promises.
The report claims that hunger has reached “epic proportions” since the technology was developed. Besides this, only two GM “traits” have been developed on any significant scale, despite investments of tens of billions of dollars, and benefits such as drought resistance and salt tolerance have yet to materialise on any scale.
Most worrisome, say the authors of the Global Citizens’ Report on the State of GMOs, is the greatly increased use of synthetic chemicals, used to control pests despite biotech companies’ justification that GM-engineered crops would reduce insecticide use.
In China, where insect-resistant Bt cotton is widely planted, populations of pests that previously posed only minor problems have increased 12-fold since 1997. A 2008 study in the International Journal of Biotechnology found that any benefits of planting Bt cotton have been eroded by the increasing use of pesticides needed to combat them.
Additionally, soya growers in Argentina and Brazil have been found to use twice as much herbicide on their GM as they do on conventional crops, and a survey by Navdanya International, in India, showed that pesticide use increased 13-fold since Bt cotton was introduced.
Micheal D. K. Owen is a professor of agronomy and an extension weed scientist at Iowa State University. He is the co-author of “The Impact of Genetically Engineered Crops on Farm Sustainability in the United States.”
Weeds, like all organisms, respond to selection pressures imposed by the environment. In this case, the primary selective pressure is the repeated use of one specific herbicide: glyphosate.
If farmers adjust their approach to weed control, they’ll be fine.
The solution to the problem for farmers who have yet to cause the evolution of glyphosate-resistant weeds is to adopt a more diverse weed management program that includes tactics other than glyphosate. By altering the selection pressure on the weeds, glyphosate resistance will be slow to evolve.
For those increasing number of farmers who have glyphosate-resistant weeds, the solution is similar but more difficult: adopt alternative tactics that will control those weeds. Of course, often these weeds have also evolved resistance to other herbicides, which, again, is attributed to the historic use of one herbicide as the sole management tactic. In this case, weed control may be more challenging and costly.
Weeds have demonstrated the ability to evolve resistance to herbicides predating the relatively recent adoption of glyphosate-resistant crops. The concern is that crop production systems (corn, soybean, cotton, sugar beets and canola) are now predominantly based on the use of glyphosate. Unless growers use more integrated weed management tactics, the problem of evolved glyphosate-resistance in weeds will likely continue to increase at a growing rate.
While it is unlikely that consumers will experience a direct impact with higher food prices, the farmers will have greater production costs and more difficult management decisions.
As far as what this problem infers about production agriculture is more difficult to assess. However, based on my experience, the risk of herbicide-resistant weeds can be addressed effectively by observing some basic principles of ecology and adjusting management tactics.
Scott M. Swinton is a professor of agricultural, food and resource economics at Michigan State University. He developed WEEDSIM, a computer program to help farmers choose profitable weed control strategies.
Roundup Ready™ crops let corn and soybean farmers rely on a single weapon. A single weapon is predicable, and any warrior who is predictable is open attack by opponents that can adjust. Roundup resistant weeds have done just that.
A choice between higher environmental costs and higher food costs for nonchemical weed control.
To overcome these new “super weeds,” farmers need to take a leaf from Sun Tzu’s “The Art of War”: study the opponent and find its weaknesses. The past 30 years of research into weed management have yielded two important keys to understanding the weaknesses of weeds.
The first key is to study the weeds in the crops. How many weeds are there? Just a few weeds may not cause enough crop damage to be worth the effort and cost of weed control. Which weed species are present? All weeds are not equal. Some weeds get bigger and do more damage than others.
There are many herbicides to choose from, and some kill certain weeds better than others. Computer programs can help farmers decide whether a herbicide is worthwhile and, if so, which one is most cost-effective. WeedSOFT is one program developed by researchers at 17 land-grant agricultural universities that can help farmers find the weapon to exploit their enemies’ weaknesses.
The second is to be unpredictable. Farmers who grow Roundup Ready™ crops may find that glyphosate is nearly always the most cost-effective choice, but the wise warrior also understands the value of surprise. Relying on the same herbicide will eventually favor those weeds that can mutate to survive.
There are many strategies farmers can use to vary their attack. They can change herbicides. They can use tillage. They can also rotate different types of crops. Rotating summer crops (like corn and soybean) with winter crops (like wheat and canola) can break up weed cycles.
Alas, studying the enemy takes time and effort. Just as antibiotic-resistant germs have forced physicians to spend more time on diagnosis, so glyphsate-resistant weeds will force farmers to spend more time on weed diagnosis. This will raise their weed control costs. Unfortunately, many herbicide substitutes for glyphosate are more toxic, so the public may have to choose between higher environmental costs and higher food costs for nonchemical weed control.
Blake Hurst farms in northwestern Missouri with his family, raising corn, soybeans and greenhouse crops.
We used to control weeds by cultivating. Three triangular shovels ran between each row of crops, rooting out weeds. We were left with weeds that had tap roots and tough stalks, which slid around the shovels. Sort of a forerunner of herbicide-resistant weeds, when you think about it. We’d cut the escapes with a hoe, which was my summer job.
We used to control weeds the old-fashioned way — with hoes.
Then, we had an outbreak of shattercane, a grass closely related to grain sorghum, which seemed to thrive on the crop protection chemicals we had at the time. Shattercane seeded so profusely that the cultivator was ineffective, and would grow back from below the ground after we cut it with a hoe. A plant that was hoe resistant.
Then, we had Roundup, which ended the threat from shattercane. But some of those wily weeds have evolved to defeat Roundup, and the war between man and weed goes on. No different than it has since the beginning of time.
We haven’t noticed a large problem with Roundup-resistant weeds on our farm because we only use Roundup every other year, and we use crop protection chemicals with different modes of action to lessen the chance of resistant weeds. We will no doubt see an increase in resistant weeds, and we’ll perhaps have to lengthen the time between applications of Roundup to maintain its effectiveness.
None of this is surprising. Of course weeds evolve, and certainly some farmers have overused a wonderful tool, just as doctors have over prescribed antibiotics. Being a technological optimist, I assume that weed scientists and crop geneticists are working overtime to solve the problem. Martial metaphors are disturbing to those who imagine farming as a pastoral stroll with Gaia, but we’re in an arms race with weeds, and thus has it always been.
Can anything be done about herbicide-resistant weeds in U.S. crops?
The herbicide is as important for global food production as penicillin is for human health.
The short answer is yes. This starts with realizing that glyphosate — Roundup and other trade names — is a precious resource for current and future harvests. Glyphosate is the world’s greatest herbicide. In my view glyphosate is a one-in-a-hundred-year discovery that is as important for global food production as penicillin is for global human health.
Yet glyphosate is failing in corn, soybean and cotton crops in the American Midwest and South because of massive overuse. This is also happening in Argentina and Brazil. For some U.S. grain and cotton producers it is already too late: over-reliance on glyphosate has led to the evolution of glyphosate-resistant weeds, and alternative chemical and non-chemical solutions will be required.
However, for many, glyphosate is still working, and these farmers have the opportunity to make changes now to give themselves the best chance that glyphosate will work for future harvests. This will call for diversifying crops and giving glyphosate a rest by using other herbicides and non-chemical weed control tools that make sense. Diversity offers the best chance of saving glyphosate.
Glyphosate should be conserved for future harvests in the U.S. and world crops because without glyphosate, global grain production becomes more difficult. And that will have a large effect on the global food supply.
By THE EDITORS
American farmers’ broad use of the weedkiller glyphosphate — particularly Roundup, which was originally made by Monsanto — has led to the rapid growth in recent years of herbicide-resistant weeds. To fight them, farmers are being forced to spray fields with more toxic herbicides, pull weeds by hand and return to more labor-intensive methods like regular plowing.
What should farmers do about these superweeds? What does the problem mean for agriculture in the U.S.? Will it temper American agriculture’s enthusiasm for genetically modified crops that are engineered to survive spraying with Roundup?