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Re: [SG] Herbicides

Bobbi,
> (A) glyphosate herbicides (e.g., Round-up)?
I use RoundUp according to label directions for edging; for killing sod
pre-tilling; and for spot control especially of perennial weeds.  It is an
extremely effective (albeit slow-acting) herbicide.

To me, this is a matter of scale.  For small areas, RoundUp is a
convenience.  In small areas, it is almost as easy to control weeds with a
hoe, or with the Butch Ragland newspaper-and-mulch trick.  On larger areas,
or when time is limiting, RoundUp certainly has utility.  I help to
maintain ornamental gardens for family relatives who live 3+ hrs from us.
RoundUp controls the weeds in the border areas much more time-efficiently
than I could by hand, because my hands spend so little time there.

That being said, there is a fair amount of literature on the potential
negative impacts of RoundUp.  Here is a link that has a lot of
environmental studies re RoundUp impacts:
Extoxnet  http://ace.ace.orst.edu/info/extoxnet/

In all fairness, most of these reports deal with ecosystem impacts, and as
such, the negative impacts would probably be true for any herbicide use.
For example, if you kill the vegetation in an area, you should expect the
population of herbivores (things that eat the vegetation) to decline.  When
the plant eaters go away, the things that eat the plant eaters will then go
away.  All of this makes sense, and to me, is not necessarily
RoundUp-specific.

If you have specific questions after looking at some of the literature, let
me know.

RoundUp will bind to the soil, and there should be little movement from the
location where you spray it.  If you spray on a windy day, the aerosol
containing the herbicide will drift in the air: be careful.  I tend to mix
up a 2 gal pump-up sprayer at a time, and the droplets can actually bounce
from one leaf to another.  I have lost plants by being a little
over-aggressive with the RoundUp sprayer nozzle.

> (B) soap-based fatty acid herbicides (e.g., Sharpshooter)?
The detergent-based herbicides work OK, too.  They function by dissolving
the waxy layer off the plant, thus permitting the plant to dry out when
exposed to sun and dry air.  Normal soil bacteria and fungi should cause
the detergent herbicides to decompose relatively quickly, assuming that you
have an adequate amount of precipitation (and in IN, you will).  The water
dilutes the concentration of the detergent in the soil, allowing bugs to
grow and consume what's there.  When the concentration is high, bugs don't
grow because they lose water to the detergent.  As it rains, the detergent
gets diluted and the bugs can begin to chew it up.

Except for concentrated spills, which have to dilute and decompose over
time, the detergent herbicides should be relatively innocuous.  They will
also work best on young weed seedlings (soft water-full tissue), and worst
on mature (tough, dry) weeds.  I would not expect these herbicides to have
much effectiveness at all on mature perennial weeds.

You should also expect these herbicides to be most effective when applied
in the early morning of bright sunny days.  A cloudy rainy day could see no
impact at all: the rain would wash the detergent away, and the weed would
lose no water and not dry up.

Rick Grazzini
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