Carcinogenic Glysophate? Organic Farming Offers Alternatives

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September 17, 2015 - Glyphosate, the active ingredient in the weed killer Roundup, is the most intensively used pesticide in the United States. Following a 2015 report that classified the herbicide as a probable carcinogen from the United Nation’s International Agency for Research and Cancer, the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA) has published its intent to list glyphosate as a known carcinogen in California.

The concerns that glyphosate is a carcinogen and that it is used so intensively enhance the importance of organic weed management, and reducing our dependence on glyphosate in agriculture. Weed control techniques used by more than 19,000 organic operations in the U.S. can be powerful tools available to all farmers in order to reduce the use of glyphosate and other herbicides.

The latest EPA data on pesticide use, from 2007, shows that glyphosate is by far the most-used pesticide at a rate of 180 to 185 million pounds per year. It is the most-used pesticide of any category, including insecticides, herbicides and fungicides. Although the EPA does not have a current report on pesticide use rates, the number of acres planted with herbicide-tolerant corn and soy has increased substantially from 2007 to 2015. There has been a major shift from the mid 1990s when little glyphosate was used on corn and soy crops, to 2010, with the great majority of corn and soy acres treated with glyphosate (USDA, 2015; Figure 1). The intensive use of glyphosate represents a change in farming practices due to the technology of genetically modified crops, and also a set of new risks for the environment and human health from glyphosate pollution.

 

Figure 1.  Herbicide use trends for soy and corn planted from 1996-2012.

 

Pollution problem

As a result of the widespread use of glyphosate in agriculture, U.S. Geological Survey monitoring has shown that glyphosate and its breakdown product AMPA are ubiquitous in the environment (Battaglin et al., 2014).

The research shows that glyphosate or AMPA are present in the majority of streams, large rivers, precipitation, agricultural ditches and drains, and soil and sediment sampled from 2001-2010 in the USGS study (Battaglin et al., 2014; Figure 2). In addition, the prevalence of glyphosate and AMPA in the environment was higher in samples from 2006-2010 than from 2001-2005, demonstrating that the increased use of glyphosate directly translates to increased pollution. The pollution caused by glyphosate creates risks, especially as drinking water sources become contaminated. The new classification of glyphosate as a known carcinogen in California heightens the need for curtailed use and more sustainable weed management practices.

 

Figure 2. Presence of glyphosate and AMPA in sampled sites (USGS, 2014).

Organic solutions

Weed management is a challenge on all farms, and is particularly difficult on organic farms. However, weed management practices employed on organic farms offer alternatives to glyphosate and other herbicides that can be applied to all farms. Organic weed control techniques employ a multitude of strategies. Careful planning and implementation of organic weed control methods successfully control weeds in organic systems. Some organic strategies explained in detail in Smith et al. (2000) include: pre-germination of weeds, burying drip irrigation to only water crops, increasing crop competitiveness, reducing the weed seed bank, weed cultivation, flame weeding, soil sterilization, mulches, using weeder geese, and new organic herbicides.

Knowing which of these techniques to use depends on the specific scale of the farming operation, the climate conditions, the unique soil and weed characteristics of the farm, and the skills and equipment available to the farmer. These weed control techniques are being used on over 19,000 organic operations in the U.S., and they can also be used to replace some of the herbicide use in conventional agriculture. By using these organic practices to reduce the amount of herbicides, like glyphosate, we would see benefits of cleaner water and reduced health risks.

 

By Joanna Ory, OFRF Research Associate