Glyphosate decreases yield, seedling quality of Roundup Ready soybeans; increases rate of fungal disease

(NaturalNews) The blockbuster herbicide glyphosate (marketed as Roundup) causes toxic effects even to plants supposedly engineered to resist it, according to a study conducted by Brazilian researchers and published in the journal Planta Daninha. The researchers found that use of glyphosate on Roundup Ready soybeans led to an increase in fungal infections and to lower crop yields.

The study offers another blow to herbicide-resistant crops, which are increasingly coming under fire for promoting increased use of toxic chemicals without actually benefiting farmers through increased crop yields.

Even resistant crops are poisoned

Following their introduction in the 1990s, herbicide-resistant crops were widely adopted by farmers in a variety of countries, including the United States and Brazil. The new study was carried out over two seasons in Roundup Ready soybean fields in Mandaguari, Parana, Brazil. It was a randomized trial consisting of five separate applications of glyphosate.

The researchers found that glyphosate treatment led to increased infection with a fungus that causes leaf blight. In addition, increased doses of glyphosate led to a reduction in the proportion of seedlings that came up normal. The study also suggested that soybean yield decreased as glyphosate dose increased.

"The results indicate that there is potential for damage by glyphosate... which are most likely related to or arise from potential injuries or the deleterious action of glyphosate," the researchers wrote.

"[C]hanges in the nutritional balance and physiology of the plant as a whole, as well as in photosynthesis and other biosynthetic processes, can lead to decreased biomass accumulation in the tissues of agronomic interest, with potential negative effects in not only plant development but also the productivity and quality of seed harvested."

Herbicide "arms race"

Another recent study also concluded that glyphosate use did not increase crop yield in Roundup Ready crops. This finding came from a joint scientific report by the environmental agencies of Austria and Switzerland and the German nature conservation agency, BfN, which reviewed the existing research on the safety and effects of herbicide-resistant genetically engineered (GE) crop cultivation.

Rather than increasing yields, the report said, the primary motivation for using herbicide-resistant crops is to reduce costs for farmers. This benefit is largely enabled by the current low prices of herbicides.

Although herbicide-resistant crops are also touted as reducing use of toxic chemicals, the report found that the opposite was the case. In the first few years after the adoption of herbicide-resistant crops, herbicide use did decrease. Since 2000, however, herbicide use in GE fields has increased every single year.

This is because the use of herbicide-resistant crops encourages farmers to rely exclusively on just one or two herbicides for weed control, and to apply those chemicals in ever larger does. This, in turn, creates selective pressure for the evolution of new Roundup-resistant weeds, which leads farmers to use even higher doses of glyphosate, and so on.

Herbicide-resistant crops have also been in the news more because the U.S. Environmental Protection Agency is considering approval of new GE corn and soy varieties engineered for resistance not just to glyphosate but also to the Agent Orange ingredient 2,4-D.

"This is part of a growing problem, an escalating chemical arms race going on across America's heartland," wrote the Center for Food Safety at Dow-Watch.org. "Dow Chemical is hyping GE 2,4-D corn and soy as the solution to resistant weeds, but GE crop systems caused the 'superweeds' in the first place. Like Roundup before it, 2,4-D is only a temporary solution that will require more and more toxic chemicals leaching into our environment and food supply."

Sources for this article include:

http://www.scielo.br

http://www.gmwatch.org

http://www.bfn.info [PDF]

http://www.nature.com

http://dow-watch.org