22 Jan 2013

A blog I wrote last May was titled “Infamy” after the great line for Kenneth Williams in Carry on Cleopatra, “Infamy, infamy, they have all got it in for me”. The blog was about the persecution of glyphosate by the anti-GM movement.

Well, the persecution is unremitting. Perhaps in many ways this could be good news. The protesters have thrown all they can at GM glyphosate tolerant crops and yet the worldwide adoption (excluding Europe!) of this technology increases significantly with each passing year. So now those who oppose it have fixed their sights upon the non-GM part of the issue, the herbicide glyphosate.

It reminds me of the advice given out to Americans and Australians during their gold rushes: the only sure way to make money out of a gold rush is to sell pickaxes.

The constant stream of negative statements appears to be having some effect. Some leading farmers are saying that they want to cut down the use of glyphosate because it reduces soil health and affects biodiversity: both aspects feature strongly in the anti-glyphosate literature.

Personally, I have no objection to cutting down on the reliance on glyphosate, particularly when direct drilling is adopted. This is the arable situation where we would expect herbicide resistance to develop most rapidly, because there is no seed shed in previous years being returned to the soil surface layers by cultivations. Hence, there is no slow down in the process of selecting for resistance.

However, to reduce glyphosate usage based on the evidence presented by the anti-GM movement is another thing. The protesters may be quoting scientific papers, but some of these have been authored by those who appear to share the same view. The recent scandal about GM maize apparently causing cancer seems to come into this category.

The protesters may also be quoting results of experiments done by objective scientists but who espouse their own personal interpretation of the results. An example of the latter is a paper published by a researcher from Rothamsted in the 1970s. In this experiment, a very large population of common couch was treated or not treated with glyphosate shortly before winter wheat was established. The winter wheat got more Take-all where glyphosate was used. The simplistic interpretation is that the glyphosate use was the cause of the additional Take-all. In reality, the researcher proved that the glyphosate killed the couch rhizomes but not the Take-all on the rhizomes so it moved to the wheat.

Finally, the anti-GM lobby may well be quoting the results of good experiments but the treatments are not directly related to what will occur in commercial practice. They may be laboratory based experiments or field experiments that use far higher doses than those used in practice.

Due to the charges made by the protesters, there have been reviews of all the available data on glyphosate. One was written for the US Department of Agriculture which concluded “scientific accounts about increased plant disease and mineral nutrition problems in GR [glyphosate resistant] crops are based on publications from a limited number of researchers. In the context of the entire body of relevant science, the significance of these reports is questionable.”

Another review paper concludes “although some laboratory tests have shown effects on nitrogen-fixing bacteria and soil fungi, effects are typically observed only under artificial laboratory conditions and at glyphosate concentrations well above normal field application rates”.

Finally, a review on the impact of glyphosate on biodiversity concludes “In summary, the literature supports the conclusion that non-target arthropods are at minimal risk from glyphosate and its formulations in offsite areas. Within treated areas, applications of the herbicide can produce changes in species diversity and in population size and structure for beneficial insects through modifications of available food sources and habitat.” 

So, the major impact of glyphosate on biodiversity is that it kills vegetation, i.e. what we use it for in Europe.  When used in GM glyphosate tolerant crops its extra efficacy may have some effect on biodiversity. However, sympathetically managed the opposite could well be true.

The associated issue is, if not glyphosate use in order to kill annual weeds prior to drilling...what do we use? Adopting additional cultivations may have a much more negative impact on the environment and the soil. In Europe the only alternative non-selective herbicides are diquat and glufosinate but neither is as effective as glyphosate on grass weeds. In addition, glufosinate is under risk of withdrawal in Europe because it may exceed some of the hazard criteria that are now being used in the registration process.

Although I will stand accused by some of being a ‘Monsatan lackey' or following my own agenda, I would rather back the views of mainstream science.