(Sorry, I've ignored this thread for as long as I can, even though
the broad brush characterization of 'chemicals' is one of my
pet peeves.)


Using the term 'herbicide' to describe a chemical that kill plants
is a lot like using the term 'animal' to describe something that eats
plants. There are many, many herbicides, ranging from the very old
method of salting the ground to glyphosate (Brand names Rodeo or Round-up)
which has virtually no known toxicity to mammals. Herbicides can
be broad spectrum (meaning they kill all photosynthetic plants), or
specific to a group of plants (some herbicides kill dicotyledonous
(broad-leaved) plants and have little or no effect on monocots (like grasses).
The important characteristics of a herbicide, or any pesticide, are

a) What is its residence time in the environment and how does that
vary with soil, weather, etc?

b) How target-specific is it?

c) Does it break down to form materials that mey be more toxic than
the original? (The famous downside of DDT)

d) In normal manufacturing, are any unintentional products produced?
(The famous downside of 2,4,5-T, aka, Agent Orange)

e) What is its acute and chronic toxicity to non-target organisms?

I do not own stock in Dow, Dupont, or any other pesticide manufacturer,
but the knee-jerk response to pesticide use is a fine
example of throwing the baby out with the bathwater. All pesticides
should be rigorously tested and used with care, but it doesn't hurt
to remember that no-till agriculture would be impossible without
herbicides.

Kelly Cassidy
U of WA
Seattle, WA 98105