[MAIPC] Glyphosate's effects on trees and soil microbia

[frazmo]

Just to amplify on what Art discusses, from my layperson/volunteer
perspective and what I synthesized in my head from years of reading and
ruminating about glyphosate --

I have not seen convincing data that glyphosate itself is particularly
risky to humans or other animals. Although obviously assertions have been
made, including the assertion that it is a carcinogen. However, it does
seem clear that some of the surfactants that have been used with the
glyphosate active ingredient ARE hazardous, especially to amphibians. Art
touches on this point that it is important to distinguish between potential
hazards of glyphosate and adjuvants or so-called "inerts" that may be mixed
with it to improve absorption. At least in theory, glyphosate-based
formulations that are approved and labeled for use in or near wetlands
should be safe for aquatic critters. We should always be alert for new data
that point to significant risks.

My own view, similar to views expressed by others, is that the responsible
use of herbicides may be a necessary evil given the destructive impacts of
invasive plants. But herbicide use should always be minimized, and we
collectively must be very aware of the risks of creating and exacerbating
herbicide resistance. Legally and ethically, the label must be followed.
And where there are realistic alternatives to herbicide use, we should
pursue them.Cheers,

Steve Young of Arlington VA, volunteer, etc.

On Wed, Oct 18, 2017 at 12:04 PM, Art Gover <aeg2 at psu.edu> wrote:

> Hi, All.
>
> A few quick points.
>
> The brief synopses Damien linked don’t match the content of the linked
> articles.
>
> The PSU article describes the persistent effect of sub-lethal doses of
> glyphosate absorbed through thin, pigmented bark.  No dispute with that.
> Larry Kuhns at PSU demonstrated that in the 1990’s - nursery treated plants
> would show symptoms years later after installation in the landscape.  Root
> absorption is not described.
>
> The Michigan State article emphasized bark absorption of triclopyr, not
> glyphosate, while treating poison ivy.  Plus, it’s a caution, not an
> observation.  Also, it does not touch on ester vs. amine formulations,
> which will likely make a difference.  No negative glyphosate effect
> described.
>
> The third article has no credibility - no citations and no direct
> observations.  Summaries of summaries.
>
> Therefore, there really isn’t anything to refute, based on those three
> sources.
>
> Granted, not necessarily the most useful approach in such matters, but
> true.  It’s a typical situation - being asked to argue against broad sweeps
> with narrowly-focused experimental data - i.e. “prove my concerns aren’t
> valid”, as opposed to asking “what data do you have to support your
> concerns?"
>
> Dewey makes a great point - it’s complicated, and 1) to date, no one has
> demonstrated a largely-negative effect of glyphosate on the soil
> microbiome.  Effects yes, ecosystem-level negative effects, no; and 2)
> science is not built to support negatives - it is most clear when
> describing what does happen, not what doesn’t happen.  In this instance,
> each side of a debate needs to provide their best evidence.  Land managers
> can provide data showing effects on exudates and therefore rhizosphere
> microbial communities - but everything we do will impact the soil
> microflora - physical disturbance, changing light and moisture conditions,
> changing plants.  Those opposed to herbicides, at this point, cannot
> provide evidence that using glyphosate to manipulate the composition of a
> plant community causes a larger negative effect than the presence of the
> exotic species.
>
> The Relyea papers are a different issue.  Good science, poorly
> communicated.  He clearly demonstrated the negative impact of certain
> adjuvants on amphibians.  He did not do a good job of differentiating
> “Roundup” (meaningless in terms of specific product description) from a
> specific product with a specific composition of glyphosate and inert
> (regulatory inert, not biological inert) ingredients.
>
> Be well.
>
> Art
>
> Penn State Wildland Weed Management
> 116 ASI Building
> University Park, PA  16802
>
> (814) 863-9904
> (814) 863-6139 FAX
> http://plantscience.psu.edu/wildland
>
> > On Oct 18, 2017, at 09:17, Ossi, Damien (DOEE) <damien.ossi at dc.gov>
> wrote:
> >
> > I am trying to convince the land managers in my city (Greenbelt, MD) to
> start managing the invasive plants on some of their land.  I am getting
> some pushback from a community group that says there’s proof that
> glyphosate will kill or damage trees and soil biota.  I’ve been looking for
> published papers that would support of refute their arguments, but have
> been unable to find much. (I don’t have access to JSTOR, BioOne, etc.)
> >
> > They are citing the following documents:
> >
> > (1) Pennsylvania Extension Service:  Tree roots absorb glyphosate; it
> has a much longer half-life than when it is in the soil.  A single
> glyphosate application results in ,persistent stunted leaf growth.
> https://extension.psu.edu/use-glyphosate-with-care-near-trees
> >
> > (2) Michigan Extension Service: Herbicides that touch the bark of
> mature, healthy trees may be absorbed by the outer bark and negatively
> affect the adjacent vascular tissue.http://msue.anr.msu.
> edu/news/be_careful_where_you_spray_that_stuff
> >
> > (3) Glyphosate interferes with the ability of tree roots to absorb
> manganese, zinc, iron, and boron from the soil; resulting in root rot,
> reduced cold hardiness, and reduced drought hardiness.http://homeguides.
> sfgate.com/effect-glyphosate-tree-roots-29076.html
> >
> > Does anyone have any resources that address these issues, or is there
> any known comprehensive document that reviews and summarizes independent
> research on the effects on glyphosate in forest ecosystems?
> >
> > Thanks,
> >
> > Damien
> >
> > Damien P. Ossi
> > Wildlife Biologist
> > Fisheries and Wildlife Division
> > Department of Energy & Environment
> > Government of the District of Columbia
> > 1200 First Street NE, 5th Floor
> > Washington, DC 20002
> > Desk: (202) 741-0840
> > Web: doee.dc.gov
> >
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