Monsanto's Roundup—the glyphosate-based pesticide—is currently the most heavily used weed killer in the country, but its efficacy is waning as farmers across the nation are reporting Roundup-resistant 'superweeds' and pesticide resistant insects taking hold in their fields and leaving farmers with no option but to return to controversial chemicals like 2,4-D, also known as Agent Orange.
In lieu of new developments in weed management to combat the failing of Monsanto's Roundup to effectively manage pests and weeds, 2, 4-D (2,4-Dichlorophenoxyacetic acid) the oldest chemical pesticide used heavily in the 1940s and '50s is now returning as a popular defense against the growing number of resistant weeds. One of the main ingredients in Dow's Agent Orange, 2, 4-D is a known drifter, and can spread easily to neighboring crops. While the EPA does not consider 2,4-D cancer causing, the International Agency for Research on Cancer classifies it as a 2B carcinogen (possibly carcinogenic to humans).
Dow is now also working on genetically engineered plants including the popular Roundup Ready Monsanto corn and soy that will be resistant to both glyphosate and 2, 4-D. They're expected to roll out in 2013 and 2015 respectively.
Also returning to fields is dicamba (3,6-dichloro-2-methoxybenzoic acid), an organochlorine compound, and like glyphosate, it's known to cause plants to become resistant to its pesticide protection. Dicamba is not considered cancer causing, but it has been linked to liver malfunction and fertility issues. It also has undesirable effects on soil quality, notably reduced nitrification; and it has been found in considerably high concentrations in ground water. Scientists at Monsanto and BASF are working on a glyphosate-dicamba 'system' that is due to hit the market by 2015 for soy, cotton and then corn.
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Image: Christian Haugen