Conor,
I am a graduate student in Rick Relyea's lab at the University of
Pittsburgh. Our lab has been looking at the direct and indirect impacts of
many types of pesticides on amphibians for the better part of this decade.
We have found that the direct impacts of pesticide exposure on amphibians
varies considerably depending on the mode of action of the pesticide, as
well as the species of amphibian. For example, we have found that some
herbicides, such as Roundup, are incredibly deadly to amphibians at
concentrations well below EPA standards. It's not the chemical itself, but
the surfactant that is highly toxic to many species of amphibians, but does
not . However, other herbicides such as Atrazine are not very lethal to
amphibians in concentrations that are likely to be observed in surface
waters.
Malathion is likely to be the insecticide that would be sprayed on
crops and wetlands for pest control and can be directly lethal to amphibians
at doses that could follow a direct overspray application. Our lab is just
discovering that endosulfan, another commonly applied insecticide, is
incredibly lethal to amphibians in concentrations as low as 1 ppb, way below
the estimated environmental concentrations according the the EPA. If
Endosulfan use in the area is high, I would not be surprised if it was at
least partially responsible for declines in amphibian populations. I hope
this helps with the "quasi-silent spring" bit of your question.
For additional information please see:
For direct impacts of malathion:
Relyea, RA. 2004. Synergistic impacts of malathion and predatory
stress on six species of North American tadpoles. *
Environmental Toxicology and Chemistry*; (23) 1080-1084.
For direct/indirect impacts of a suite of herbicides/insecticides:
Relyea, RA. 2009. A cocktail of contaminants: how mixtures of
pesticides at low doses effect aquatic communities. *Oecologia*;
(159) 363-376.
Relyea, RA
Will Brogan
On Thu, Jul 9, 2009 at 12:10 PM, Paul Cherubini <[email protected]> wrote:
> Conor_Flynn wrote:
>
> > we've noticed something interesting: there are no
> > mosquitoes in or near Alamosa. This is because the
> > city sprays for them regularly. We have also noticed
> > fewer grasshoppers, bees, and frogs than we might
> > otherwise expect.
>
> Michael Cooperman wrote:
>
> > I don't know what chemical your county uses for mosquito
> > control but probably it is not specific to mosquitoes and
> > would affect other insects just as strongly.
>
> Interesting these comments suggesting great harm to
> both mosquitoes and non-target insects appeared just after
> Mitch Cruzan said: "Critical thinking/reading is a primary goal
> of all graduate programs and is something we introduce
> undergraduates to in advanced courses."
>
> A critical thinker would say it wildly speculative for anyone to
> claim, without extensive direct evidence, that:
>
> 1) There really are no mosquitoes and fewer grasshoppers, bees,
> and frogs in Alamosa, Colorado.
>
> 2) Mosquito spraying is the underlying cause of these declines.
>
> Paul Cherubini
> El Dorado, Calif.
>
--
William R. Brogan III
University of Pittsburgh
Department of Biology
101 Clapp Hall
Pittsburgh, PA 15224
"Not everything that counts can be counted, and not everything that can be
counted counts."
-Albert Einstein
