GM Free Cymru

Glyphosate has strongly negative effects on crops and field ecology

Scientists finding many negative impacts of Roundup Ready GM crops

USDA doesn’t want to publicize studies showing negative impacts

Robert Kremer is a microbiologist with the US Department of Agriculture’s Agricultural Research Service and an adjunct professor in the Division of Plant Sciences at the University of Missouri. He is co-author of one of five papers published in the October 2009 issue of The European Journal of Agronomy that found negative impacts of Roundup herbicide, which is used extensively with Roundup Ready genetically modified crops. Kremer has been studying the impacts of glyphosate, the primary ingredient in Monsanto’s Roundup herbicide, since 1997.

The Organic & Non-GMO Report interviewed Mr. Kremer about his research and the reluctance of the USDA to publicize the findings of the five papers.

Please give me an overview of your research RK: We started in 1997 wanting to see if this new system, Roundup Ready, would change the production of nematodes in soybean. We started looking at organisms in soybean roots and saw microorganisms colonizing the roots. We suspected that glyphosate was having an impact. There was a root fungi problem that seemed to be encouraging sudden death syndrome (SDS). We saw the increase of these fungi in the Roundup Ready (genetically modified) system, both soybeans and corn.

What types of things are you seeing in the Roundup Ready system? RK: This system is altering the whole soil biology. We are seeing differences in bacteria in plant roots and changes in nutrient availability. Glyphosate is very systemic in the plant and is being released through the roots into the soil. Many studies show that glyphosate can have toxic effects on microorganisms and can stimulate them to germinate spores and colonize root systems. Other researchers are showing that glyphosate can immobilize manganese, an essential plant micronutrient.

What are glyphosate’s impacts on beneficial soil bacteria? RK: The most obvious impact is on rhizobia, a bacterium that fixes nitrogen. It has been shown that glyphosate can be toxic to rhizobia. (Nitrogen fixing bacteria are important to soils because nitrogen is the most commonly deficient nutrient in many soils.)

What about research showing increased incidence of Fusarium in Roundup Ready GM crops? RK: We’ve taken field surveys and seen an increase in Fusarium with the use of glyphosate. Some Roundup Ready varieties even without using glyphosate tend to be more susceptible to being impacted by Fusarium. It could be an unintended consequence of genetic manipulation that could make it more susceptible.

Your paper also mentioned the potential of glyphosate to contaminate groundwater. RK: Yes, under certain circumstances. The big assumption for claims that glyphosate is benign is that it isn’t immediately absorbed by the soil. But research is showing that isn’t necessarily true; that it is still available in the soil. If soil is full of phosphorous, glyphosate could leach into ground water. For example, farmers may use manure from confined animal feeding operations as a fertilizer. The soil will then contain high amounts of phosphorus, which overwhelms the soil. Any glyphosate that hits the soil will be a potential contaminant. It can stay in the soil or it might run off into streams or waterways.

What about glyphosate resistant weeds? RK: We have eight different species of glyphosate resistant weeds in Missouri. Some species of Johnson Grass are found in fields where Roundup is used year after year. It is a very aggressive weed. To solve the problem of weed resistance, genetic engineers are developing soybeans that tolerate Roundup and Dicamba, another herbicide. They are incorporating another gene resistant to another herbicide. When resistance happens again, will they then develop a plant resistant to five or six herbicides? It’s an illogical circle.

With so much glyphosate being used, what types of long-term impacts do you think could occur? RK: We are already seeing glyphosate-resistant weeds. If we continue to use glyphosate in the same fields year after year, it’s a matter of time until microbial communities in the soil will shift to more detrimental species. The use of glyphosate stimulates detrimental pathogens in the growing season but they go back down after the growing season. Eventually, they may build up in the soil and not go back down.

Are many researchers looking at the possibly negative impacts of glyphosate or Roundup Ready crops? RK: There are a handful of researchers. There is more research looking at the production of these crops.

The papers published in the European Journal of Agronomy received no publicity in the United States. Why is that? RK: I was working with USDA-ARS to publish a news release about these studies. I’ve gone all the way to the administrators, but they are reluctant to put something out. Their thinking is that if farmers are using this (Roundup Ready) technology, USDA doesn’t want negative information being released about it. This is how it is. I think the news release is still sitting on someone’s desk.

What about your future research? RK: We’re looking at some methods that could be used to overcome negative effects if we continue to use Roundup Ready crops, such as supplementation of nutrients by foliar application. I’m more interested in sustainable agriculture. More farmers are interested in using cover cropping to maintain soil quality and other organic amendments. But it’s a steep learning curve for them.

[[NOTE from GM Free Cymru: these findings are directly relevant to the safety / environmental impact assessments of RR crops. According to the EU Directives, when GM crops are considered, both direct and indirect effects have to be examined. If indirect negative effects (eg damage associated with applications of Roundup or other glyphosate products) are clearly established, that would be a sufficient reason for refusal of consent.]]

The key references:

European Journal of Agronomy Volume 31, Issue 3, Pages 111-176 (October 2009) Glyphosate Interactions with Physiology, Nutrition, and Diseases of Plants: Threat to Agricultural Sustainability?, Mineral Nutrition and Disease Problems in Modern Agriculture: Threats to Sustainability? Piracicaba-SP, Brazil 20-21 September 2007 Edited by Robert J. Kremer, Tsuioshi Yamada, Paolo R. de Camargo e Castro and Bruce W. Wood

articles 1 - 10

1. Acknowledgements Page iv

2. Glyphosate interactions with physiology, nutrition, and diseases of plants: Threat to agricultural sustainability? Pages 111-113 Tsuioshi Yamada, Robert J. Kremer, Paulo Roberto de Camargo e Castro, Bruce W. Wood

3. Glyphosate reduced seed and leaf concentrations of calcium, manganese, magnesium, and iron in non-glyphosate resistant soybean Pages 114-119 Ismail Cakmak, Atilla Yazici, Yusuf Tutus, Levent Ozturk

4. Turfgrass species response exposed to increasing rates of glyphosate application Pages 120-125 Y. Senem Su, L. Ozturk, I. Cakmak, H. Budak

5. Glyphosate in the rhizosphere—Role of waiting times and different glyphosate binding forms in soils for phytotoxicity to non-target plants Pages 126-132 Tsehaye Tesfamariam, S. Bott, I. Cakmak, V. Römheld, G. Neumann

6. Glyphosate associations with cereal diseases caused by Fusarium spp. in the Canadian Prairies Pages 133-143 M.R. Fernandez, R.P. Zentner, P. Basnyat, D. Gehl, F. Selles, D. Huber

7. Glyphosate effects on diseases of plants Pages 144-152 G.S. Johal, D.M. Huber

8. Glyphosate and glyphosate-resistant crop interactions with rhizosphere microorganisms Pages 153-161 Robert J. Kremer, Nathan E. Means

9. Influence of glyphosate-resistant cropping systems on weed species shifts and glyphosate-resistant weed populations Pages 162-172 William G. Johnson, Vince M. Davis, Greg R. Kruger, Stephen C. Weller

10. A simple chromatographic assay to discriminate between glyphosate- resistant and susceptible soybean (Glycine max) cultivars Pages 173-176 E.A. Bonini, M.L.L. Ferrarese, R. Marchiosi, P.C. Zonetti, O. Ferrarese-Filho