Roundup: The perfect storm for plant disease
More than 30% of all herbicides sprayed anywhere contain glyphosate—the world’s bestselling weed killer. It was patented by Monsanto for use in their Roundup brand, which became more popular when they introduced “Roundup Ready” crops starting in 1996. These genetically modified (GM) plants, which now include soy, corn, cotton, canola, and sugar beets, have inserted genetic material from viruses and bacteria that allows the crops to withstand applications of normally deadly Roundup.
(Monsanto requires farmers who buy Roundup Ready seeds to only use the company’s Roundup brand of glyphosate. This has extended the company’s grip on the glyphosate market, even after its patent expired in 2000.)
The herbicide doesn’t destroy plants directly. It rather cooks up a unique perfect storm of conditions that revs up disease-causing organisms in the soil, and at the same time wipes out plant defenses against those diseases. The mechanisms are well-documented but rarely cited.
1. The glyphosate molecule grabs vital nutrients and doesn’t let them go. This process is called chelation and was actually the original property for which glyphosate was patented in 1964. It was only 10 years later that it was patented as an herbicide. When applied to crops, it deprives them of vital minerals necessary for healthy plant function—especially for resisting serious soilborne diseases. The importance of minerals for protecting against disease is well established. In fact, mineral availability was the single most important measurement used by several famous plant breeders to identify disease-resistant varieties.
2. Glyphosate annihilates beneficial soil organisms, such as Pseudomonas and Bacillus bacteria that live around the roots. Since they facilitate the uptake of plant nutrients and suppress disease-causing organisms, their untimely deaths means the plant gets even weaker and the pathogens even stronger.
3. The herbicide can interfere with photosynthesis, reduce water use efficiency, lower lignin , damage and shorten root systems, cause plants to release important sugars, and change soil pH—all of which can negatively affect crop health.
4. Glyphosate itself is slightly toxic to plants. It also breaks down slowly in soil to form another chemical called AMPA (aminomethylphosphonic acid) which is also toxic. But even the combined toxic effects of glyphosate and AMPA are not sufficient on their own to kill plants. It has been demonstrated numerous times since 1984
5. The actual plant assassins, according to Purdue weed scientists and others, are severe disease-causing organisms present in almost all soils. Glyphosate dramatically promotes these, which in turn overrun the weakened crops with deadly infections.
“This is the herbicidal mode of action of glyphosate,” says Don. “It increases susceptibility to disease, suppresses natural disease controls such as beneficial organisms, and promotes virulence of soilborne pathogens at the same time.” In fact, he points out that “If you apply certain fungicides to weeds, it destroys the herbicidal activity of glyphosate!”
By weakening plants and promoting disease, glyphosate opens the door for lots of problems in the field. According to Don, “There are more than 40 diseases of crop plants that are reported to increase with the use of glyphosate, and that number keeps growing as people recognize the association between glyphosate and disease.”