Researchers Find Over Time Roundup is Not Effective on Weeds


(Beyond Pesticides, August 18, 2006)

Research conducted at the University of Kansas (KU) showed findings that the popular herbicide Roundup (glyphosate) could lose its effectiveness on weeds over time. The research team, which included Ernst Schnbrunn, associate professor of medicinal chemistry, and Todd Funke, doctoral student at KU, analyzed the protein that makes certain crops resistant to the herbicide Roundup, chemically named glyphosate. The study was recently published in the peer-review journal Proceedings of the National Academy of Sciences. The team’s findings suggest that the farming industry might need to develop a new weed killer or develop better management practices that are environmentally friendly.

Successful alternative least-toxic weed strategies are available with prevention being the key to managing weeds. Cultural practices have been proven to be the single most effective method of weed management. In states such as Wyoming, noxious weeds are being successfully controlled with Cashmere goats. (See PAY Vol. 21, No 4 2001.)

During the 1990s Monsanto found a bacteria that could resist Roundup in a production factory where the herbicide was highly concentrated. Crops were given a DNA sequence from the resistant bacteria and were then able to make a protein that allowed them to resist Roundup. The crops were dubbed Roundup-Ready. Weeds do not possess the same protein and thus are killed by the herbicide.

According to Mr. Funke, Roundup-Ready crops have been on the market for years, but no one knew exactly what allowed this protein to work. Dr. Schnbrunn said results of their research indicates that weeds could soon become resistant to Roundup, as did the bacteria in the production factory, because the chemical change needed for plants to resist the herbicide is so minor. Dr. Schnbrunn continued, “The scary thing is that glyphosate, or Roundup, is commercially very successful because it is toxic to plants but doesn’t harm animals or the environment and that all other known herbicides are more poisonous to animals and cause more environmental damage.” Exposure to glyphosate can cause asthma-like symptoms and breathing difficulty. Undisclosed, or proprietary, ingredients (called “inert ingredients”) in Roundup, a common formulation of glyphosate, have been linked to pneumonia and damage to the mucous membrane tissue and the upper respiratory tract.

Symptoms following exposure to glyphosate formulations include: swollen eyes, face and joints; facial numbness; burning and/or itching skin; blisters; rapid heart rate; elevated blood pressure; chest pains, congestion; coughing; headache; and nausea. In developmental toxicity studies using pregnant rats and rabbits, glyphosate caused treatment-related effects in high dose groups, including diarrhea, decreased body weight gain, nasal discharge and death. A 2002 peer-reviewed study finds children born to parents exposed to glyphosate (Roundup) show a higher incidence of attention deficit disorder and hyperactivity. EPA material safety data sheets for the common herbicides glyphosate (Roundup), 2,4-D, mecoprop, and dicamba, (often combined as Trimec) list them as respiratory irritants that can cause irritation to skin and mucous membranes, chest burning, coughing, nausea and vomiting.

According to Mr. Funke, “there is a bright side to the team’s findings that could lead to the development of drugs that fight microbial infections, such as pneumonia or malaria.” Mr. Funke continued, “All bacteria, plants, fungi and many parasites use this protein, but humans don’t. So there’s a lot of interest in designing chemicals to stop this protein from functioning.” The researchers plan to search for chemicals that target this protein in order to develop new antibiotics and herbicides.

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