Scientists Reveal Glyphosate Poisons Crops and Soil
Glyphosate-tolerant (GT) crops have spread rapidly around the
world since they were introduced in the US in 1996, and are now
planted on 85 percent of the global area growing genetically
modified (GM) crops [1]. Concomitantly, glyphosate (commercial
formulation Roundup), promoted as safe for health and the
environment, became the most widely used herbicide in the world.
But ecological and health impacts of the GT cropping system soon
came to light, and have been worsening relentlessly over the
years while regulators turn a blind eye (see [2, 3]
Roundup Ready
Sudden Death, Superweeds, Allergens...,
SiS 28;
Ban Glyphosate Herbicides Now,
SiS 43).
Glyphosate binds with and inactivates EPSPS, the critical
enzyme in the shikimate pathway required for the synthesis of
aromatic plant metabolites including essential amino acids
phenylalanine, tryptophan and tyrosine, as well as downstream
products such as plant growth promoter, indoylacetic acid and
plant defence compounds, phytoalexins [4]. But glyphosate has
multiple adverse effects that act synergistically on crop health
and productivity that extends well beyond the plant into the
soil ecosystem and the wider environment.
The GT trait depends on incorporating an EPSPS from the soil
bacterium Agrobacterium
tumefaciens that is insensitive to glyphosate, hence
glyphosate is taken up by GT plants and translocated to the
growing parts of roots and shoots, and even exuded into the
rhizosphere (soil surrounding the roots) so it can affect the
soil community of microorganisms and also subsequent crops
planted in the soil.
Two senior scientists in the US who have been investigating
the ecological impacts of glyphosate and the Roundup Ready
cropping system for decades are warning of “dire consequences
for agriculture such as rendering soils infertile, crops
non-productive, and plants less nutritious.”
Glyphosate the single most important factor predisposing plants to
diseases and toxins
Don Huber, recently retired from Purdue University, and co-author G.S.
Johal, at Purdue’s Dept of Botany and Plant Pathology, stated in a paper
published in the October 2009 issue of European Journal of Agronomy
that the widespread use of glyphosate in the US can “significantly
increase the severity of various plants diseases, impair plant defense
to pathogens and diseases, and immobilize soil and plant nutrients
rendering them unavailable for plant use.”
Further, glyphosate stimulates the growth of fungi and enhances the
virulence of pathogens such as Fusarium, and “can have serious
consequences for sustainable production of a wide range of susceptible
crops.” They warn that “Ignoring potential non-target detrimental side
effects of any chemical, especially used as heavily as glyphosate, may
have dire consequences for agriculture such as rendering soils
infertile, crops non-productive, and plants less nutritious.”
In an interview [5] with the Organic & Non-GMO Report, Huber
said he has been researching glyphosate for 20 years, and began noticing
problems when he saw a consistent increase in “take-all”, a fungal
disease of wheat, when glyphosate had been applied in a previous year to
control weeds. He found glyphosate reduced manganese in plants, which is
essential to many plant defence reactions against disease and
environmental stress. Glyphosate can immobilize plant nutrients such as
manganese, copper, potassium iron, magnesium, calcium, and zinc, so they
are no longer nutritionally functional. Basically, glyphosate completely
weakens the plant, making it susceptible to soil-borne fungal pathogens.
“That is one reason why we see an increase in plant diseases,” he said.
There has been a general increase in the number of plant diseases in
the past 15 to 18 years. Four primary soil fungi, Fusarium,
Phythium, Rhizoccccctonia, and Phytophthora, have
become more active with the use of glyphosate; and concomitantly,
diseases caused by these fungi have increased, such as head scab in
corn, or root rot in soybeans, crown rot in sugar beets. Fusarium head
blight, which affects cereal crops, is a disease that produces a
mycotoxin that could enter the food chain.
There are more than 40 diseases reported with the use of glyphosate,
and the number keeps growing as people recognize the association, Huber
said.
When asked if glyphosate is “environmentally benign” as claimed by
proponents, he answered “Absolutely not. That’s an outright mistaken
notion. Glyphosate is the single most important agronomic factor
predisposing some plants to both disease and toxins. These toxins can
produce a serious impact on the health of animals and humans.
“Toxins produced can infect the roots and head of the plant and be
transferred to the rest of the plant.” Huber explained. “The toxin
levels in straw can be high enough to make cattle and pigs infertile.”
One way in which glyphosate can affect human health is that
“micronutrients such as manganese, copper, potassium, iron, magnesium,
calcium, and zinc are essential to humans. All of them can be reduced in
availability by glyphosate; so glyphosate treated GT plants as well as
other plants exposed to glyphosate have less mineral nutrients. “We are
seeing a reduction in nutrient quality [in our food].”
“The [Roundup Ready] gene will reduce micronutrient efficiency up to
50 percent for zinc and manganese…This could also account for the yield
drag [reported for GT soybeans].”
“Unfortunately, most researchers are forbidden to do work in the
area. They don’t have access to isogenic lines [conventional and Roundup
Ready plant lines that are otherwise genetically identical], the
materials are denied to researchers.”
Huber and Johal recommend using as little glyphosate as possible.
Unfortunately, reducing the dose of glyphosate will be insufficient
for killing weeds, particularly as numerous weeds are becoming highly
resistant to the herbicide (see [6]
GM Crops
Facing Meltdown in the USA, SiS 46)
Roundup Ready system alters the whole soil biology
Robert Kremer is a microbiologist with the USDA-ARS (US Department of
Agriculture- Agricultural Research Service) and an adjunct professor in
the Division of Plant Sciences at the University of Missouri. He started
in 1997 to investigate how the new Monsanto Roundup Ready system
(Roundup herbicide and GT cropping) would change the level of nematodes
in soybean. His research team began looking at the roots and saw
microorganisms colonizing the roots, and suspected that glyphosate was
having an impact. There was a root fungi problem that seemed to
encourage sudden death syndrome.
In fact, the system is “altering the whole soil biology.” Kremer told
The Organic & Non-GM Report [7]. “We are seeing differences in
bacteria in plant roots and changes in nutrient availability. Many
studies show that glyphosate can have toxic effects on [some]
microorganisms and can stimulate [others] to germinate spores and
colonize roots systems. Other researchers are showing that glyphosate
can immobilize manganese, an essential plant micronutrient.”
Glyphosate is toxic to beneficial bacteria like rhiozbia, which fixes
nitrogen, but increases the incidence of pathogens like Fusarium.
“Some Roundup Ready varieties even without using glyphosate, tend to be
more susceptible to Fusarium,” possibly an unintended effect of
genetic modification.
If the soil is full of phosphate (as when livestock manure is used as
a fertilizer), glyphosate could leach into ground water (and poison
other wild-life and human beings).
“We saw the increase of these fungi in the Roundup Ready system, both
soybeans and corn.” Kremer said.
The papers describing the work of his research team, published in the
European Journal of Agronomy [8] received no publicity in the US.
Kremer said [7]: “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.”
Kremer concluded [7]: “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,” but
added, “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.”
References
1. Yamada T. Kremer RJ. De Carmargo e Castro and Wood BW. Glyphosate
interactions with physiology, nutrition, and diseases of plants: threats
to agricultural sustainability? Europ J Agronomy 2009 31, 111-3
2. Ho MW and Cummins J. Roundup Ready sudden death, superweeds,
allergens…time to wipe GM crops off the globe.
Science in Society
28, 26-27, 2005.
3. Ho MW. Ban glyphosate herbicides now.
Science in Society
43, 34-35, 2009.
4. Johal GS and Huber DM. Glyphosate effects on diseases of plants.
Eur J Agron 2009, 144-52.
5. “Scientist warns of dire consequences with widespread use of
glyphosate”, The Organic & Non-GMO Report, May 2010,
http://www.non-gmoreport.com/articles/may10/consequenceso_widespread_glyphosate_use.php
6. Ho MW. GM crops facing meltdown in the USA. Science in Society 46
(in press).
7. “Scientist finding many negative impacts of Roundup Ready GM
crops, USDA doesn’t want to publicize studies showing negative impact2,
The Organic & Non-GMO Report, January 2010,
http://www.non-gmoreport.com/articles/jan10/scientists_find_negative_impacts_of_GM_crops.php
8. Kremer RJ and Means NE. Glyphosate and glyphosate-resistant crop
interactions with rhizosphere microorganisms. European Journal of
Agronomy 2009, 31, 153-61.
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