Un des avantages de cultiver des OGM, des Organismes Génétiquement Modifiés, selon les compagnies qui les possèdent, est la résistance de la récolte à un herbicide spécifique, permettant, promet-on, de diminuer l'épandage des herbicides, réduisant ainsi les dépenses et la pollution.
Mais malheureusement ce qui devait arriver arriva: non seulement les OGM insecticides encouragent le développement d'insectes insensibles à ces nouvelles plantes inventées par l'homme, mais la surutilisation de l'herbicide Roundup de Monsanto, ou glyphosate si vendu par les autres, a encouragé la prolifération des "mauvaises herbes" qui sont maintenant insensibles à cet herbicide, les rendant très difficile à éradiquer. Les fermiers doivent donc retourner aux anciennes façons de désherber un champ: soit utiliser des herbicides plus toxiques, soit les arracher à la main ou tout simplement faire les labours plus souvent.
"On retourne 20 ans en arrière!" se plaint un agriculteur. On espérait qu'à faire des semis directs et diminuer au minimum le labourage, on limitait l'érosion des sols et la migration des intrants vers les fossés et les cours d'eau. Mais la nature s'adapte à tout, et la liste des plantes qui ne sont plus tuées par les herbicides allonge. Les premières plantes résistantes aux herbicides ont été identifiées dans un champs de soya au Delaware en 2000. Depuis ce temps-là, il y en a partout: il y a 10 espèces de plantes résistantes dans 22 états, et elles se resèment dans des millions d'acres, surtout dans des champs de soya, de maïs-grain et de coton.
Les agriculteurs ont tellement arrosé de Roundup sur des récoltes OGM Roundup Ready qui peuvent le tolérer (90% du soya et 70% du maïs-grain et du coton sont Roundup Ready aux USA) que les "mauvaises herbes" se sont adaptées du style "évolution de Darwin haute-vitesse" selon un scientifique de l'université de l'Iowa. Des "mauvaises herbes" résistantes au Roundup comme la vergerette et l'herbe à poux géante forcent les agriculteurs à retourner à des méthodes plus dispendieuses qui avaient été mises de côté avec les nouveautés OGM. Une plante particulièrement agressive et envahissante est apparue au Tennessee seulement l'an passé: une amarante dont le nom commun est "pigweed" peut croître de 3 pouces (7,5 cm) par jour et atteint 7 pieds ou plus, étouffant les récoltes. En plus, elle est si solide qu'elle endommage l'équipement agricole.
Mais la leçon n'est pas encore apprise: Monsanto et d'autres compagnies développent d'autres récoltes génétiquement modifiées pour résister à d'autres herbicides. Bayer vent déjà du coton et du soya résistant au glufosinate, un autre herbicide. Le nouveau maïs de Monsanto tolère le glyphosate et le glufosinate, tout en développant d'autres récoltes qui résistent au dicamba, un pesticide qui existe depuis un bout de temps. Syngenta travaille sur un soya qui tolère ses produits Callisto. Dow Chemical travaille sur un maïs et du soya qui résistent au 2,4-D, un composé du Agent Orange, le défoliant utilisé durant la guerre du Vietnam.
Une parenthèse personnelle: il n'existe pas de "mauvaises herbes"; il y a seulement des plantes qui poussent aux mauvais endroits (selon les humains)!
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"U.S. Farmers Cope With Roundup-Resistant Weeds
For 15 years, Eddie Anderson, a farmer, has been a strict adherent of no-till agriculture, an environmentally friendly technique that all but eliminates plowing to curb erosion and the harmful runoff of fertilizers and pesticides. But not this year. On a recent afternoon here, Mr. Anderson watched as tractors crisscrossed a rolling field — plowing and mixing herbicides into the soil to kill weeds where soybeans will soon be planted. Just as the heavy use of antibiotics contributed to the rise of drug-resistant supergerms, American farmers’ near-ubiquitous use of the weedkiller Roundup has led to the rapid growth of tenacious new superweeds. To fight them, Mr. Anderson and farmers throughout the East, Midwest and South are being forced to spray fields with more toxic herbicides, pull weeds by hand and return to more labor-intensive methods like regular plowing.
“We’re back to where we were 20 years ago,” said Mr. Anderson, who will plow about one-third of his 3,000 acres of soybean fields this spring, more than he has in years. “We’re trying to find out what works.” Farm experts say that such efforts could lead to higher food prices, lower crop yields, rising farm costs and more pollution of land and water. “It is the single largest threat to production agriculture that we have ever seen,” said Andrew Wargo III, the president of the Arkansas Association of Conservation Districts.
The first resistant species to pose a serious threat to agriculture was spotted in a Delaware soybean field in 2000. Since then, the problem has spread, with 10 resistant species in at least 22 states infesting millions of acres, predominantly soybeans, cotton and corn. The superweeds could temper American agriculture’s enthusiasm for some genetically modified crops. Soybeans, corn and cotton that are engineered to survive spraying with Roundup have become standard in American fields. However, if Roundup doesn’t kill the weeds, farmers have little incentive to spend the extra money for the special seeds.
Roundup — originally made by Monsanto but now also sold by others under the generic name glyphosate — has been little short of a miracle chemical for farmers. It kills a broad spectrum of weeds, is easy and safe to work with, and breaks down quickly, reducing its environmental impact. Sales took off in the late 1990s, after Monsanto created its brand of Roundup Ready crops that were genetically modified to tolerate the chemical, allowing farmers to spray their fields to kill the weeds while leaving the crop unharmed. Today, Roundup Ready crops account for about 90 percent of the soybeans and 70 percent of the corn and cotton grown in the United States.
But farmers sprayed so much Roundup that weeds quickly evolved to survive it. “What we’re talking about here is Darwinian evolution in fast-forward,” Mike Owen, a weed scientist at Iowa State University, said. Now, Roundup-resistant weeds like horseweed and giant ragweed are forcing farmers to go back to more expensive techniques that they had long ago abandoned. Mr. Anderson, the farmer, is wrestling with a particularly tenacious species of glyphosate-resistant pest called Palmer amaranth, or pigweed, whose resistant form began seriously infesting farms in western Tennessee only last year. Pigweed can grow three inches a day and reach seven feet or more, choking out crops; it is so sturdy that it can damage harvesting equipment.
In an attempt to kill the pest before it becomes that big, Mr. Anderson and his neighbors are plowing their fields and mixing herbicides into the soil. That threatens to reverse one of the agricultural advances bolstered by the Roundup revolution: minimum-till farming. By combining Roundup and Roundup Ready crops, farmers did not have to plow under the weeds to control them. That reduced erosion, the runoff of chemicals into waterways and the use of fuel for tractors. If frequent plowing becomes necessary again, “that is certainly a major concern for our environment,” Ken Smith, a weed scientist at the University of Arkansas, said. In addition, some critics of genetically engineered crops say that the use of extra herbicides, including some old ones that are less environmentally tolerable than Roundup, belies the claims made by the biotechnology industry that its crops would be better for the environment.
Roundup-resistant weeds are also found in several other countries, including Australia, China and Brazil, according to the survey. Monsanto, which once argued that resistance would not become a major problem, now cautions against exaggerating its impact. “It’s a serious issue, but it’s manageable,” said Rick Cole, who manages weed resistance issues in the United States for the company. Of course, Monsanto stands to lose a lot of business if farmers use less Roundup and Roundup Ready seeds. Monsanto and other agricultural biotech companies are also developing genetically engineered crops resistant to other herbicides.
Bayer is already selling cotton and soybeans resistant to glufosinate, another weedkiller. Monsanto’s newest corn is tolerant of both glyphosate and glufosinate, and the company is developing crops resistant to dicamba, an older pesticide. Syngenta is developing soybeans tolerant of its Callisto product. And Dow Chemical is developing corn and soybeans resistant to 2,4-D, a component of Agent Orange, the defoliant used in the Vietnam War."
Excerpts from article written by William Neuman and Andrew Pollack published in The New York Times here: http://www.nytimes.com/2010/05/04/business/energy-environment/04weed.html
Interesting editorial debate in The New York Times (and telling photographs&graphics!) here: http://roomfordebate.blogs.nytimes.com/2010/05/06/invasion-of-the-superweeds/
May I add that weeds are just plants we decided didn't belong there!
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