The December/January 2010 issue of The
Organic & Non-GMO Report featured an interview with Robert
Kremer, an adjunct professor in the Division of Plant Sciences
at the University of Missouri, whose research showed negative
environmental impacts caused by glyphosate, the main ingredient
in Monsanto's Roundup herbicide, which is used extensively with
Roundup Ready genetically modified crops.
The following interview is with another scientist, Don Huber,
who recently retired from Purdue University, who has also
documented negative environmental impacts from glyphosate.
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The widespread use of glyphosate is causing negative impacts on
soil and plants as well as possibly animal and human health.
These are key findings of Don Huber, emeritus professor of plant
pathology, Purdue University.
Compromise agricultural sustainability, animal and human health
In a paper published in the European Journal of Agronomy in
October 2009, Huber and co-author G.S. Johal, from Purdue's
department of botany and plant pathology, state that the
widespread use of glyphosate that we see today in agriculture in
the United States can "significantly increase the severity of
various plant diseases, impair plant defense to pathogens and
diseases, and immobilize soil and plant nutrients rendering them
unavailable for plant use." Further, the authors state that
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." The authors warn "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. To do otherwise
might well compromise not only agricultural sustainability, but
also the health and well-being of animals and humans."
Please tell me about your research with glyphosate.
Don Huber: I have been doing research on glyphosate for 20
years. I began noticing problems when I saw a consistent
increase in "take-all" (a fungal disease that impacts wheat)
where glyphosate had been applied in a previous year for weed
control. I tried to understand why there was an increase in
disease with glyphosate.
I found that glyphosate has an effect on reducing manganese in
plants, which is essential to many plant defense reactions that
protect plants from 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.
Glyphosate kills weeds by tying up essential nutrients needed to
keep plant defenses active. Glyphosate doesn't kill weeds
directly but shuts down their defense mechanisms so pathogens in
the soil can mobilize and kill the weeds. 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.
Glyphosate causes plants to be more susceptible and greatly
stimulates the virulence of pathogens that kill plants.
How many plant diseases are linked to glyphosate?
DH: There has been a general increase in the number of plant
diseases in the last 15 to 18 years.
There are four primary soil fungi-Fusarium, Phythium,
Rhizoctonia, and Phytophthora- that become more active with the
use of glyphosate.
There has been an increase in take-all, Fusarium diseases, such
as head scab, Gibberella (Fusarium) in corn, Pythium,
Corynespora or root rot in soybeans, crown rot in sugar beets,
and bacterial and fungal diseases. 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 use of glyphosate,
and that number keeps growing as people recognize the
association (between glyphosate and disease).
Has research confirmed the link between glyphosate and Fusarium?
DH: There is plenty of data to show that, and it raises concerns
about toxins in food.
Can you give an example of a specific crop that has been
negatively impacted by glyphosate?
DH: Last summer I visited farms that had typical glyphosate
damage. I received a call from a potato seed farmer in Minnesota
who grows 1000 acres of seed potatoes. There was so much
glyphosate in the potato tubers from a previous crop of Roundup
Ready soybeans that the potatoes can't be used as seed and could
not be certified.
Proponents of glyphosate say it is environmentally benign. Would
you agree with that assessment?
DH: 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. The toxin levels in
straw can be high enough to make cattle and pigs infertile.
In your paper you say that "the introduction of such an intense
mineral chelator as glyphosate into the food chain through
accumulation in feed, forage, and food, and root exudation into
ground water, could pose significant health concerns for animals
and humans and needs further evaluation." Could you elaborate on
this?
DH: Micronutrients such as manganese, copper, potassium, iron,
magnesium, calcium, and zinc are essential to human health. All
of them can be reduced in availability by glyphosate; mineral
nutrients are less in glyphosate treated plants. We are seeing a
reduction in nutrient quality (in food crops).
There are also reports of allergic reactions, such as stomach
lesions, produced by the Roundup Ready (genetically modified)
gene.
These reactions need to be studied; there needs to be a lot more
information that we don't have. This type of research has been
prevented by a lack of access to information.
What other impacts do you see caused by the Roundup Ready gene?
DH: The gene will reduce micronutrient efficiency up to 50% for
zinc and manganese. It's very significant unless the plant is
supplemented with micronutrients. This could also account for
the yield drag (reported with Roundup Ready crops).
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.
In your paper you recommend using as small a dose of glyphosate
as possible. Why is this?
DH: To my knowledge we've never had this much reliance on one
herbicide. It's hard to find an acre in the US that hasn't had
glyphosate applied on it in the last three years.
We need to have judicious use of glyphosate and remediate the
damage that it does. If we continue to abuse the use of
glyphosate, it's just a matter of time before we see more
serious negative ramifications. We will have increasing toxin
levels (in crops), reduced nutrient values, and the direct
presence of glyphosate in crops.
There are a lot of serious questions about the impacts of
glyphosate that we need answers for in order to continue using
this technology. I don't believe we can ignore these questions
any more if we want to ensure a safe, sustainable food supply
and abundant crop production.