2,4-D - every bite a killer

April 2011

Roundup herbicide and its active ingredient, glyphosate, have been getting a lot of bad press recently.  But it seems there's worse to come.


In 1997, just when the first GM Roundup Ready crops were emerging in the fields, Monsanto scientists were successfully arguing against any possibility that weeds might also manage to make themselves Roundup Ready.

The evidence to support thier argument seemed to be that, in over 20 years of worldwide use, there had been no verified evidence of weeds evolving resistance to glyphosate (the key herbicidal ingredient in Roundup).  This success was put down to glyphosate's unique chemical structure and metabolism, its unique mechanism of plant-annihilation, and the lack of residual activity in the soil.  Moreover, even if the weeds did begin to become tolerant, they would still be so weakened by the glyphosate, they wouldn't survive.  Weeds with tricks up their sleeves, such as stacks of duplicated genes to overwhelm the herbicide, were dismissed as “unlikely” (see WEEDS HAVE TRICKS UP THEIR SLEEVES - Archive news, February 2010).

Common marestail. Image Wiki Commons
As early as 2001, the first glyphosate-resistant marestail weeds were noticed: farmers began to find themselves with a problem which hadn't previously been a problem.  Add to this that warnings were already sounding about a reduction (by up to 17%) in rental value of any farmland with uncontrolled weeds, with glyphosate-resistance as the No.1 concern.

The manufacturers of Roundup and Roundup Ready seed, however, continued to be dismissive.  In 2003, Monsanto International's technical manager was telling soyabean farmers "If I were in growers' shoes, I would look for effective, cost-efficient weed control, which is what Roundup provides.  If it's a dead weed, it won't produce seed.”  He assured customers that many growers  had used Roundup Ready soyabeans (plus Roundup) continuously for eight years without any problems, and that long-term university research had demonstrated that growers could successfully grow Roundup Ready crops in rotation with each other.  Complaints about the emergence of problematic glyphosate-resistant waterhemp  were blamed on the farmers' bad management: they were taking too long to get around to applying the Roundup, and then using it at too low a concentration for the size of the weeds.  Other grumbling about non-dead weeds were met with advice to use glyphosate at the maximum rate and to add in other herbicidal chemistries.

A policy of don't-look-don't-see was definitely in operation at this time.  One US University weed specialist pointed out that, despite glyphosate's increasing failure, “The companies aren't looking for new products.  It's just not happening”.

By 2010, 90 percent of GM crops were Roundup Ready varieties.  The population of glyphosate-resistant weeds which, in 2007, had stood at eight weed species on 3,251 sites covering 2.4 million acres, exploded into 14,262 sites covering 5.4 million acres in 2009, and mushroomed to 19 weed species on 30,000 sites covering 11.4 million acres just a year later.  Monsanto was reported to be paying farmers to spray chemicals made by other companies and some farmers were resorting to hand-weeding.  One weed scientist caused a stir by proposing to the government that it should restrict the use of herbicide-tolerant crops and impose a tax on biotech seeds to fund research and educational programmes for farmers.

The situation was clearly getting out of control ...

While Monsanto's prototype herbicide/GM-crop package was having its successes and failures, other biotech companies were watching and learning.  They could see that herbicide-tolerant GM crops were too lucrative to let slip, and that Roundup's days were numbered.  All it needed was an alternative weedkiller effective enough be sold to farmers, and safe enough to be spun to regulators.

Dow AgroSciences has come up with just such a sales package to “complement” glyphosate-resistant crops.

The new weedkiller is an old one, 2,4-D (2,4-dichlorophenoxyacetic acid), a plant-hormone mimic which has been around for some 60 years (much longer than glyphosate).

The GM genes put into crops to inactivate the 2,4-D are copied from a bacterium.  The enzyme generated by the GM genes has been found to degrade, not only 2,4-D but a variety of other herbicides.  This paves the way nicely for a deluge of chemicals on and in our food crops (providing they are GM).

2,4-D is described by Dow scientists as being low-cost, environmentally-friendly, and having low-persistence, plus low-toxicity to humans and wildlife.  If this sound suspiciously like the “glyphosate is safe as salt” sound-byte of yesteryear (see GM time-bomb - Safe as salt?  Not Roundup), the US Department of Agriculture Forest Service might agree.  The Service's 'Human Health and Ecological Risk Assessment  for the chemical notes that:
 “... many non-accidental exposure scenario – i.e. exposures that are plausible under normal conditions of use – also exceed the level (triggering) concern, and often by a very substantial margin.”
“Unless steps are taken to mitigate risks, workers involved in the application of 2,4-D and members of the general public who consume vegetation contaminated with 2,4-D could be exposed to 2,4-D levels greater than those which are generally regarded as acceptable.  In some cases, the exceedances are substantial.  Similarly, adverse effects in the normal use of 2,4-D salts of esters could occur in groups of non-target organisms including terrestrial and aquatic plants, mammals, and possibly birds.”
Regarding human exposure “Based on recent studies published in the open literature, 2,4-D is toxic to the immune system and developing immune system, especially when used in combination with other herbicides.  The mechanism of action of 2,4-D toxicity is cell membrane disruption and cellular metabolic processes.  The molecular basis for 2,4-D toxicity to human lymphocytes and nerve tissue is likely the induction of programmed cellular death known as apoptosis.”

In safety data sheets, 2,4-D is classed as 'Toxic' if swallowed or inhaled, and is described as an experimental carcinogen and teratogen which may cause central nervous system damage.


Add to all the above comments that a plant genetically transformed to resist 2,4-D and other chemicals will end up accumulating any one such chemical, maybe all of them, and/or a host of their toxic breakdown products.  People will then swallow this cocktail in their food, and inhale the cocktail in plant debris in the air.

The USDA Forest Service paints a very different, and worrying, picture of 2,4-D compared with the glowing description given by the biotech company intending to sell it.  Your future diet sounds as if it will deliver  a double whammy of fertility damage from glyphosate and immunity damage from 2,4-D, plus whatever effects there might be from whatever other chemicals are there.

That is, of course, if you decide to eat up whatever Mssrs. Monsanto and Dow have decided to feed you.  The choice is yours.

  • T. R. Wright, et al., 2010, Robust crop resistance to broadleaf and grass herbicides provided by aryloxyalkanoate dioxygenase transgenes, PNAS, 107:47
  • Human Health and Ecological risk Assessment for 2,4-0D, SDA Forest Service, 30.09.06
  • Growing Roundup-resistant weed problem must be dealt with, expert says,, 14.09.10
  • Charles Margulis, Monsanto's Superweeds Come Home to Roost, Generation Green, 26.10.10
  • As weeds become glyphosate-resistant, farmers asked to very control methods, Farm Industry News, 5.02.03
  • A. D. Bradshaw, et al., 1997, Perspectives on Glyphosate Resistance, Weed Technology 11

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