[With a note on some confusion about wheat, and if it has been genetically modified (see below)]
The herbicide 2,4 D is pretty powerful stuff. It has recently been in the news because it kills weeds that have developed resistance to glyphosate (brand name Roundup). In May, I wrote about efforts by Dow AgroSciences to bring a new genetically modified corn to market that has been engineered to be tolerant to 2,4 D.
The idea is that the new corn would withstand applications of both glyphosate and 2,4 D, and that farmers would use those two herbicides, and presumably a rotation of at least one other chemical control, to kill weeds and prevent new occurrences of resistant weeds.
Along with the new corn, Dow scientists created a new version of 2,4 D, called 2,4 D Choline, that is less likely to drift off the fields where it has been applied. Now, one group of growers, the Save Our Crops Coalition, has issued a joint statement with Dow saying that the information Dow has supplied about reduced drift and volatility, along with the company’s pledge to investigate non-target claims, has gone a long way to satisfy its concerns about migrating herbicide. Both SOCC and Dow say they have “agreed to modify positions with respect to pending regulatory matters around 2,4-D tolerant crops.”
Prior to this agreement, the Save Our Crops Coalition had used the USDA’s open comment period to request an environmental impact statement to assess the likelihood of drift from 2,4 D applications.
They pointed out that since not all farmers will be growing 2,4 D tolerant crops, drift to non-intended targets could result in significant crop damage, since it would be applied during the growing season (imaging a field of vegetables that got smogged by 2,4 D – the plants would croak along with the weeds).
I reported on Dow’s work to reduce migration of 2,4 D in the C&EN feature story. Here’s the relevant background:
David E. Hillger, an application technology specialist at Dow AgroSciences, explains that rather than traditional ester or amine forms of the molecule, which can volatilize in the environment, the new version is a more stable quaternary ammonium salt.
In addition, Hillger says Dow’s proprietary manufacturing process produces a product with less particle drift when application directions are followed. Dow recently reported that field tests of the formula showed a 92% reduction in volatility and a 90% reduction in drift.
Crops that contain the 2,4-D tolerance- trait will also tolerate older versions of 2,4-D. However, Dow has developed a stewardship program that obligates farmers to use a premixed combination of 2,4-D choline and glyphosate. The program includes farmer education about using multiple herbicide modes of action, the requirement to use Dow’s new herbicide mixture, and labeling instructions for proper application. State pesticide regulations generally require farmers to follow labeling guidelines when using herbicides.
For now DowAgrosciences is waiting on regulatory authorizations for 2,4-D tolerant corn, but the company says it plans to get the green light in time for the 2013 growing season.
Certainly there are other criticisms of the 2,4 D-tolerant crops still out there. One important concern is that farmers may use chemical fertilizers in such a way as to promote even more herbicide-resistant weeds – ones that cannot be killed with 2,4 D or glyphosate. Another is the possibility that the amount of 2,4 D used on crops will dramatically increase (glyphosate, though used in large amounts, breaks down rather quickly in soil).
And of course, foes of all types of GMO crops abound, and anyone who is against Roundup Ready corn is not likely to be in favor of the new varieties.
Speaking of which, I’ve noted a number of commentaries relating to wheat lately, apparently due to the rise of anti-gluten eating. Many leave the reader with the impression that the U.S. is awash in genetically modified wheat. This is incorrect – there are many wheat hybrids on the market today, but none have been genetically engineered.
I find it handy to refer to an online USDA list – updated seemingly daily – which lists pending GM crops as well as those that have been approved already (in the section titled Determinations of Nonregulated Status). You may want to bookmark it, or have it printed on handy cards to give to people.
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