To address this issue, one must first look at the current state of herbicide resistance and then examine the definitions of Sustainable Agriculture and the recommendations of public and private weed scientists to best manage resistance.
Resistance is not new nor is it isolated to glyphosate. The first case of resistance to a herbicide was recorded in 1957, and since this time resistance has been recorded for just about every herbicide being used today. Relative to most of the other herbicide classes, there is less resistance to glyphosate – even though no herbicide has been used more than glyphosate. While some have branded the weeds resistant to glyphosate as ‘superweeds’, weed scientists would explain that these same species have resistant populations to many other herbicides, and therefore highlighting the issue relative to only glyphosate is a misrepresentation of the facts. In short, public and private weed scientists work to reduce the risk and impact of resistance to all our herbicide resources.
As defined by USDA, there are three goals to Sustainable Agriculture:
(1) Improve farmer short-term and long-term profitability,
(2) Steward the nation’s land, air and water resources, and
(3) Improve farmers quality of life (www.sare.org).
Weeds are one of the most economically important pests that famers have to manage to ensure long-term profitability. The Weed Science Society of America has published a set of best management practices at www.wssas.net which specifies that the best way to proactively prevent or delay herbicide resistance is to employ a diversified weed management program that includes the use of multiple herbicides with overlapping activity and/or use of herbicides in combination with mechanical and/or cultural practices. The implementation of diversified programs is applicable and recommended to be used before resistance is present in a field, as well as after resistant biotypes have become established in a field. In short, multiple weed control practices in the form of multiple herbicides and/or use of herbicides in combination with non-chemical practices are base recommendations of academics, government and extension weed scientists throughout the US.
The question becomes: how does the implementation of diversified weed management programs fit with the goals of sustainable agriculture? Using the three goals listed above, the answer is as follows:
(1) Diversified weed management programs (i.e. use of multiple herbicides) improves short- and long-term profitability of farmers by increasing the yield potential of their crops. Weeds are a threat to yields and, if not effectively controlled, cause the greatest reduction in yields compared to losses due to insects and diseases. Using multiple herbicides, in mixtures or sequences, reduces the likelihood that weeds will reduce yields.
(2) Herbicides combined with diversified herbicide weed management programs are one of two main technologies that have allowed farmers to adopt conservation tillage practices. The other key technology has been in advances in planters that that can be used in heavy plant residue situations. Without herbicides, farmers would have to rely on mechanical tillage of the soil to control weeds. USDA and university researchers throughout the US have documented the environmental advantages of conservation tillage, which includes reduced soil and nutrient erosion into our streams, rivers and lakes. This practice has also addressed the significant erosion of soil by wind that occurred during the ‘dust bowl’ years in the 1930s and 1940s, when mechanical tillage was the primary method of weed control.
(3) Diversified weed management programs, in general and specifically those including glyphosate or other broad spectrum herbicides, provide greater flexibility and assurance to farmers in their ability to effectively control weeds and thus positively affect farmers’ lives.
Another environmental advantage of herbicides and diversified weed management practices is improved yield. The more yield produced per acre of farmland the less land needed to feed a growing population. This reduces land converted from native vegetation to farm production allowing more land for wildlife and increased plant diversity.
In summary, I hope you can see that there is another important side of the story relative to the value and use of herbicides and use of diversified weed management programs and the connection with Sustainable Agriculture. Monsanto’s role to provide new weed control options, as it facilitates use of diversified weed management programs and subsequently reduces the risk of resistance, is in fact very consistent with the basic goals of Sustainable Agriculture.