The latest advent in genetic crop technology – 2,4-D resistant corn and soybean crops from Dow Chemical – is renewing the three-decade long debate over genetically engineered crops for the next generation. And while it’s impossible to know how science and public opinion will ultimately resolve this fight, today’s farmers are facing more immediate questions about Dow’s latest development. Specifically, whether 2,4-D resistant crops will be the next best thing in agronomy or will they go the route of Roundup-resistant crops – creating resistant weeds in the process?
The history of pest-resistant or pesticide-resistant crops reflects significant changes that have been made in American agriculture in recent decades. Roundup-ready (glyphosate-resistant) soybeans were released for use in 1996, with the first glyphosate-resistant weeds showing up within four years and several more in the first decade of field use. Though the bacteria Bacillus thuringiensis (Bt) has been sprayed on crops since the 1950’s, killing insects and breaking down in the environment within a week, Bt GMO corn has only been available since 1998, with Bt-resistant insects showing up in 2011. So what went wrong with these wonder crops?
In the case of Roundup-ready crops, once seed was released for sale, glyphosate use increased dramatically, though it was using a less dangerous pesticide. This killed off weeds that were not glyphosate resistant, leaving a few weeds that were resistant with less competition for water, nutrients, and sunlight, allowing them to flourish and reproduce. The second way Roundup-ready crops led to resistance was by cross-pollinating with wild relative weeds in the environment. Because the wild relatives often were not in the field, resistance from this method often went unnoticed for some time.
In Bt crops, the effectiveness of spraying the bacteria on the crops directly was high because it was only done on an as-needed basis and didn’t linger in the environment, which prevented resistance from building up in insects. When Bt GMO crops were engineered, however, the toxin remained in every cell of every plant in the environment, creating a consistent exposure to the toxin. Because it did not have a direct route to resistance through cross-pollination such as the Roundup-ready weeds, Bt-resistant insects took longer to become apparent on the scene, a little over three times as long.
A USDA comment period on the 2,4-D resistant corn variety and two soybean varieties was run in January and February. Among the statements from the USDA at this time included,
“Dow AgroSciences’ GE corn and soybean plants are the first developed to be resistant to 2,4-D and are intended to provide farmers with new plants to help address the problem of weeds that have developed resistance to other herbicides.”
There was an immediate and strong outcry from natural food proponents, who began referring to these GMOs as “Agent Orange” crops.
Though 2,4-D has been used for decades as a relatively mild and safe pesticide, it was also one of the two pesticides used in Agent Orange, spurring great debate and controversy in the natural foods sector. Agent Orange has been related to a large number of extremely serious side effects and diseases, especially in military veterans who were exposed during their time in Vietnam. What these advocates don’t mention is that it is the other pesticide, 2,4,5-T, that causes these effects and that it has been removed from the market for those reasons.
The concern with 2,4-D resistant crops relates most strongly to the fast development of Roundup-resistant crops. If 2,4-D is used in these new crops as glyphosate was in Roundup-ready crops, the fear is that we will have not one, but two pesticides that these “superweeds” are resistant to. The best possible solution is to encourage the responsible use of 2,4-D with these crops, using an effective integrated pest management (IPM) strategy. This includes regular monitoring of pests and providing the minimum effective treatment, rather than spraying crops in record amounts of pesticide.
GMO crops have a proven track record of effectiveness; how effective they remain is up to us, the farmers in the field, by using them responsibly.