GENTECH archive 8.96-97
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Roundup toxicity

Jaan Suurkula wrote:

>Considering that Roundup is very toxic to microorganisms, how does it affect
>the very complex soil microflora? Considering that the microflora has been
>found to contribute importantly to binding of Nitrogen and to the water
>absorbtion of the plants, how will the fertility of the soil be affected?
>The above mentioned agronomist asked Monsanto about this but they answered
>that the research results are secret. As it should not be in the interest of
>Monsant to hide positive results, the suspicion arises that the fertility
>studies indicated, as might be expected a negative effect on the fertility
>of the soil.


and in response to a question from me Jaan supplied the information from
Greenpeace shown at the end of this message.

         I have never argued that glyphosate is without environmental
impact, only that it is much softer than many herbicides already in use.

        Thus, I am very surprised to read that anyone was told that the
research results were secret since they have been widely reported in the
open literature for years and are a part of the Roundup registration
package filed at least in the US. Glyphosate does effect development of
many microbes in petri dishes etc.  Generally glyphosate is bound tightly
to the soil and is thus not available to influence the soil microflora to
any great extent in vivo.  It is efficacious against soil microorganisms
because they, like plants, rely on EPSPS in the shikimate pathway,  which
is not found in animals.

        In addition to the references cited by Greenpeace, you can look to

"The Herbicide Glyphosate", E. Grossbard and D. Atkinson,  eds, 1985 (all
European authors, published by Butterworth's London)

"Glyphosate a unique global herbicide", John Franz, Michael Mao and James
Sikorski,  American Chemical Society Monograph 189, Washington 1997

 and

GLYPHOSATE EFFECTS ON MICROBIAL BIOMASS IN A CONIFEROUS FOREST SOIL
 Stratten GW and Stewart KE  Environ Toicol Water Qual 7 (3) 1992
223-236.

        With respect to the Greenpeace review (at the end of this message),
the citations appear to be a bit selective.  For example, although repeated
applications (once every 14 days!) show effects on earthworms (ref 2
below), field trials involving the same and related species showed no
effect (Dalby et al. 1995, Soil Biol. Biochem. 27: 1661-1662). Although
glyphosate caused a significant short term effect on soil microbial
activity in one study, the effects disappeared in 6 months (ref 4).
Further, a paper immediately following ref 4 and by the same authors in the
same journal found no effect of glyphosate on ectomycorrhizal symbiosis of
red pine.  In fact, 46-48% of seedling pines failed to survive in
non-glyphosate treated plots, apparently due to competition with weeds,
whereas all survived in the glyphosate-treated plots (Chakravarty P and
Chatarpaul L (1990) Pestic. Sci. 28:243-247).

         The strongest case against glyphosate is that some of its
formulations  contain surfactants and that these are toxic to some fish and
frogs, and probably the earthworms in Greenpeace's reference 2.  Most or
all herbicides have some surfactants to help them stick to weeds when
sprayed

        The doses of Roundup needed to affect fish are relatively high.
Although I would be skeptical of recommendations to apply any pesticide
near water, US Fish and Wildlife Service scientists wrote that "Application
of Roundup, at recommended rates, along ditchbank areas of irrigation
canals should not adversely affect resident populations of fish or
invertebrates" (Folmar et al. Arch. Environ. Contam. Toxicol. 8:269-278;
ref 1b of Greenpeace).  Frogs in Australia may be more sensitive due to low
oxygen levels in most breeding sites (Mike Tyler, Dept of Zoology,
University of Adelaide).

        The advantages of glyphosate over other herbicides were discussed
by Netzer (1984, Bio/Technology 2:939-944).  I have never argued that
glyphosate
 is without environmental impact, only that it is much softer than many
herbicides already in use.


Rick


>TOXICITY OF GLYPHOSATE TO FISH, INVERTEBRATES AND MICROORGANISMS
>(Excerpts from an article by Greenpeace)
>
>Roundup can be toxic to fish to an extent which depends on several factors
>including the hardness of the water, the age of the fish and water
>temperature. In some situations concentrations as low as 10 parts per
>million of glyphosate can kill fish (1a and 1b)
>
>Glyphosate also affects the growth and survival of earthworms. A study in
>New Zealand showed that glyphosate caused a reduction in growth and increase
>in mortality of the most commonly found earthworm in New Zealand (2).
>
>Glyphosate is also toxic to many beneficial mycorrhiza fungi which help
>plants to take up nutrients from soils (3)(4)(5)(6)
>
>In this context it is also worth noting that glyphosate at least one study
>indicates is not immobilized indefinitely in the soil as maintained by the
>producer. Under certain conditions it has been found to be released and
>leach into the water (7).
>
>
>REFERENCES
>
>1 a World Health Organization, United Nations Environment Programme,
>International Labour Organization (1994) Glyphosate. Environmental Health
>Criteria 159. Geneva, Switzerland. See also:
>1 b Folmar L C, Sanders H O and Julin A M (1979) Toxicity of the herbicide
>glyphosate and several of its formulations to fish and aquatic
>invertebrates. Arch. Environ. Contam. Toxicol. 8:269-278
>1 c Wang Y, Jaw C and Chen Y (1994) Accumulation of 2,4-D and glyphosate in
>fish and water hyacinth. Water Air Soil Pollut. 74:397-403
>
>2 Springett J A and Gray R A J (1992) Effect of repeated low doses of
>biocides on the earthworm Aporrectodea caliginosa in laboratory culture.
>Soil Biol. Biochem. 24(12):1739-1744
>
>3 Estok D, Freedman B and Boyle D (1989) Effects of the herbicides 2,4-D,
>glyphosate, hexazinone, and triclopyr on the growth of three species of
>ectomycorrhizal fungi. Bull. Environ. Contam. Toxicol. 42:835-839
>
>4 Chakravarty P and Chatarpaul L (1990) Non-target effect of herbicides: I.
>Effect of glyphosate and hexazinone on soil microbial activity. Microbial
>population, and in-vitro growth ofectomycorrhizal fungi. Pestic. Sci.
>28:233-241
>
>5 Sidhu S S and Chakravarty P (1990) Effect of selected forestry herbicides
>on ectomycorrhizaldevelopment and seedling growth of lodgepole pine and
>white spruce under controlled and field environment. Eur J. For. Path.
>20:77-94
>
>6. Chakravarty P and Sidhu S S (1987) Effects of glyphosate, hexazinone and
>triclorpyr on in vitro growth of five species of ectomycorrhizal fungi. Eur.
>J. For. Path. 17:204-210
>
>7. Piccolo A et al. (1994) Adsorption and desorption of glyphosate in some
>European soils. J. Environ. Sci. Health B29(6):1105-1115
>