Subject: poison spraying Part 3
Date: Oct 18 21:58:37 2002
From: Allyn Weaks - allyn. at tardigrade.net


On 18/10/02, Dlrymnd at aol.com wrote:

>After speaking to Jeff, he states that they will be using a product called
>"Round-Up Pro."

Your birds should be safe then. Roundup Pro is the exactly same
ingredients as Roundup--glyphosate and a surfactant (detergent)--but
intended for commercial dilution and application. It's more
concentrated than the consumer concentrate (though still intended for
dilution in most uses) and the label instructions are different,
primarily giving more details about application rates and listing more
techniques such as stump application and agricultural use.

The official label for Roundup Pro:
<http://www.cdms.net/ldat/ld07A008.pdf> (requires acrobat reader). You
should care about labels, because the label is literally the law for
use of a pesticide--if you understand the label, and are still worried,
you can keep an eye on the application to see at least that there are
no obvious violations such as spraying in windy conditions.

The extoxnet write-up for glyphosate:
<http://ace.orst.edu/cgi-bin/mfs/01/pips/glyphosa.htm>

"Effects on birds: Glyphosate is slightly toxic to wild birds. The
dietary LC50 in both mallards and bobwhite quail is greater than 4500
ppm [1]."

LC50 is "lethal concentration 50%", the concentration needed to kill
50% of test animals. It's usually used for concentrations in air or
water over a brief period such as 4 hours, but it can be used as a
chronic exposure value, as it is here.

As a rather rough rule of thumb, LC50 is about twice the LD50, the
amount in mg/kg for a single dose to kill half the animals in the test.
That would make for an approximate bird LD50 of 2250 mg/kg, or a single
dose of 65 mg. for a one oz. bird. A white crowned sparrow weighs
about an ounce. Measure out 1/8 tsp of table salt--that's 100 mg., so
you can see that 65 mg. is quite a hefty dose.

How much glyphosate will be involved? The label states 3-4 quarts per
acre for blackberries. From the ingredients list in the same file,
Roundup Pro contains 3 pounds per gallon glyphosate. So one acre gets
about 1300 grams. At the height of berry production, one might guess
that perhaps as much as 1% of that would coat berries (a high
estimate), but at this time of year, I'd guesstimate at most 1/10 of
that. About 1.3 grams of glyphosate (at most!) spread over all of
the berries on an entire acre. I don't know how long the blocks are,
but assuming a fairly typical 500', a three block by 15' strip is half
an acre, so we're down to 0.65 grams, or 650 mg. (And that's before
the rain comes and washes it off!) If ten sparrows ate every single
bit of that in one sitting, without sharing any of it with robins, or
bugs, or other sparrows, 5 might die. Doesn't seem a likely scenario,
though, does it? For chronic exposure, you're back to using the LC50
values. At which point you need more details about how much the
critters really eat over time, so I'll leave that as an exercise for
other tweeters :-)

It's great that you contacted them to get more details. Now that you
have that contact, you might be able to take advantage of it to find
out what Children's plans to replace those berries with. If Jeff says
'grass' or some other mundane landscaping scheme, you probably have 5-6
months to convince him and his bosses that they really ought to put in
a lovely native hedgerow instead. That really would be a win for the
birds--and for the kids!
--
Allyn Weaks allyn at tardigrade.net Seattle, WA Sunset zone 5
Pacific NW Native Wildlife Gardening: http://www.tardigrade.org/natives/
"The benefit of even limited monopolies is too doubtful, to be opposed
to that of their general suppression." Thomas Jefferson