THE BORDERS OF THE NATURAL …
farming has to solve the same problems as conventional farming. In fact, it
uses many pesticides, extracts or decoctions of plants (neem extract, rotenone,
nicotine, pyrethrum, nettle liquid manure, etc.) and minerals (potassium soap,
copper, sulfur, calcium compounds or even arsenic in some countries, etc.) or
others, but whose purpose is the same, preserving the productivity of the crop.
recent years, some molecules such as spinosad, insecticide synthesized by
bacteria, were allowed in organic farming, because its production is natural,
although the process is completely industrial. In this case, it's the US giant
of chemistry, Dow Chemical that makes it.
All this is
fine, but leads us to a very serious reflection on a subject which strongly
aggravates the societal debate on the use of chemicals in agriculture.
was thinking to write a post about an article on this delicate subject from a
long time. To be honest, I did not really know how to do it.
recently, ForumPhyto published an article (http://www.forumphyto.fr/en/2016/01/07/comment-produire-un-herbicide-naturel-wackes-seppi-andrew-kniss/ )
speaks of an article by Wackes Seppi (http://seppi.over-blog.com/2016/01/comment-produire-un-herbicide-naturel.html )
translates an original article by Andrew Kniss (http://weedcontrolfreaks.com/2016/01/how-to-make-a-natural-weed-killer/ ).
as you can see, it is something like a chain reaction, but the topic results to
be not only interesting, but still quite essential.
basic question is: "when talking about pesticides, where ends the
natural?", And the corollary question "on what real criteria should
we consider a pesticide, natural or not?".
R. Kniss, University of Wyoming (USA), Associate Professor, Weed Biology &
let's talk the specialist. I fully rebuke the original article (and part of the
illustrations) by Andrew Kniss, and part of the illustrations of the French
translation by Wackes Seppi.
parts may seem very technical or scientific to you. But that is really worth
reading it up to the end.
“How to Make a Natural Weed Killer
January 6, 2016 Posted by Andrew
Well over a year ago, I wrote about
a homemade herbicide containing salt, vinegar, and dish soap.
“Many of you have probably seen it
posted to Facebook or Twitter or Pinterest, or on your favorite home gardening
site. One of my favorite descriptions calls it a “magical, natural, weed
That particular potion certainly
kills weeds, but it isn’t natural (and it certainly isn’t chemical-free). It
contains dish soap and vinegar, both of which are synthesized industrially, so
it isn’t natural by most definitions of the word. That’s disappointing, because
people really yearn for a natural weed-killer. They want to kill the weeds
around their homes and in their gardens, but they don’t like the idea of using
a synthetic pesticide. Most people (including me) would prefer to use something
natural, all else being equal. Unfortunately, there are very few truly natural
products that work as effective herbicides.
That being said, I’d like to introduce
you to a fascinating chemical named bilanaphos. In the early 1970’s, bilanaphos
was discovered independently by two different laboratories, one in Germany and
the other in Japan. Both groups isolated this chemical from Streptomyces
bacteria; S. viridochromogenes in Germany, and S. hygroscopicus by the Japanese
group. Bilanaphos is produced naturally by these naturally occurring bacteria.
So, by nearly any definition, bilanaphos is natural.
Bilanophos – a natural compound
isolated from at least two species of Streptomyces bacteria.
The scientists in Germany and Japan
both learned early-on that bilanaphos had strong weed-killing properties; when
it was applied to plants, the plants died. Upon further investigation,
scientists in the German group recognized that only part of the full bilanaphos
chemical was required for herbicidal activity. In fact, when bilanaphos enters
the plant, about half of the molecule is quickly chopped off, leaving behind a
smaller molecule – phosphinothricin. It is this smaller molecule that acts as an
herbicide in the plant.
When the naturally occurring
compound bilanaphos (left) enters the plant cell, the plant removes two alanine
residues leaving behind the chemical phosphinothricin (right). Phosphinothricin
exhibits herbicidal activity in most plants, by inhibiting the glutamine
So we have a natural compound
(bilanaphos) that is converted naturally by plants to another compound
(phosphinothricin) that works very effectively as an herbicide. And it turns
out that some Streptomyces species naturally produce a small amount of
phosphinothricin also. That sounds very much like a natural herbicide, right?
Not so fast…
Phosphinothricin (better known in
the US as glufosinate) is widely used as an herbicide today. It is the active
ingredient in herbicides like Rely (mostly used in tree and vine crops), and
Liberty (most commonly used in conjunction with Liberty Link crops). But even
though the chemical occurs naturally, and was first discovered by extracting it
from naturally occurring bacteria, the commercial herbicide is produced
synthetically. So it is not considered a ‘natural’ herbicide.
The story of phosphinothricin,
while very interesting, is not unique. A huge number of scientists around the
world are searching nature to find new chemicals that have antibiotic,
pesticidal, or other useful properties. Between 1997 and 2010, USDA scientists
estimate that about 69% of all new pesticide active ingredients registered by
the EPA were either natural products, synthetic products derived from natural
sources (like phosphinothricin), or biological in nature. For example, another
commonly used corn herbicide was discovered after an initial observation that
few plants could grow underneath a red bottlebrush bush in a garden. But weed
killers are actually the smallest component (less than 7%) of these new
pesticides of natural origin; around 30% of new insecticide or fungicide active
ingredients are either natural products or natural product-derived.
Currently, the FDA is struggling to
define the word natural on food labels. It is an often-used marketing term with
no clear definition. It may be even more difficult to define when discussing
pesticides. As the phosphinothricin example shows, the lines between natural
and synthetic can get blurred quickly. Is it natural because it occurs in
nature? Or does it have to be physically extracted from nature to be considered
The ‘natural or not‘ distinction
can distract from what is really important when discussing pesticides. If the
compound is structurally the same, the naturally occurring and the
synthetically produced versions will share the same properties. The properties
of the compound are far more important, in my opinion, than the source of the
compound. Is the pesticide safe for applicators and the environment? Does it
break down quickly in the environment to non-toxic products? If so, then I’m
much less worried about whether it is natural or not, regardless of how we
But there are questions related to
the source of the product that can be important. In particular, which has a
greater impact, synthesis in the lab? Or extraction from natural sources? I
rarely hear discussions related to this question, but this is among the most
important questions related to natural products (provided they are deemed
safe). If we can efficiently extract a renewable resource from nature, and
avoid the energy and fossil fuel requirements of synthetic production, then a
naturally produced product sounds pretty good to me. But if extracting
something from nature means we’ll have a greater negative impact on the
environment than we would producing it in a factory, then please give me the
Hoerlein (1994) Glufosinate
(Phosphinothricin), A Natural Amino Acid with Unexpected Herbicidal Properties.
p 73-145 in Reviews of Environmental
Contamination and Toxicology (Vol 138)
Dayan et al. (2011) Rationale for a
natural products approach to herbicide discovery. Pest Management Science.
Cantrell et al. (2012) Natural
Products as Sources for New Pesticides. Journal of Natural Products. 75:1231-1242. »
Andrew Kniss is Professor of Ecology and weed management at the University of
man has always be inspired by Nature to evolve. Chemists as well. Despite the
power of his imagination, man has not yet found a better source of inspiration
that Nature herself.
ultimately, we come to a relevant note, full of deep consequences:
copies of natural molecules, but manufactured synthetically, were allowed in
organic farming, most crops could find reasonable solutions for almost all of
the usual pest problems, and we could actually witness an explosion of Organic
synthetic production of natural molecules, I wonder if someone has already
addressed a question, yet fundamental: what agricultural area should be devoted
to the production of natural molecules, if the entire global agricultural
production become organic?
it reasonable, in view of a population of 9 to 10 billion people or more, not
to devote maximum resources to the production of food and raw materials, by
pure ideological concerns?
So when will
the organic ideology relax its criteria so that integrated farming can at last
find its rightful place?
we give the chemistry of the imitation of nature a greater protagonism?
Are we sure
that the extraction of natural substances are not detrimental to the
environment, and the staff who works there?
it not high time that we reasonably study the real needs, disregarding the
limits established by the dogma?
We know how
to make a very environment friendly agriculture, while being productive,
efficient to solve the problems of humanity, not wasting, and reasonably
profitable for farmers.
current state of knowledge and available means, contrary to what some claim, it
is not possible to make a 100% organic production of food to feed 7.5 billion
inhabitants. However, it would be possible to do in a very high percentage, if
we accept the "pesticides copies".
It is very
damaging to everyone that the debate has been so corrupted by shortsighted
dogma, culminating in recent years on an authentic "agri-sharia" true
holy war against chemistry, without any deep reflection, based above all on a
media hype, without impartial scientific support, essentially repeating past
denies today, that the "Green Revolution" has had negative
consequences in many respects, despite its good original intentions.
But the lack
of scientific knowledge was the basis of these errors, and the needs of the
post-war justified it.
changed a lot in 50 years, but it seems that only farmers know that.
real political support, and a few good Media corrections may be enough to put
the record straight.