Is there any such thing as a non-target species
Michael Gochfeld
gochfeld at eohsi.rutgers.edu
Mon Oct 4 06:20:39 EDT 1999
I was intrigued by Paul Cherubini's response to my posting regarding
West Nile Virus and malathion spraying.
First an update. Last night, Westchester County (southeastern New York
State adjacent to New York City) announced a weeklong plan to spray the
entire northern part of the county based on the finding of some dead
crows (numbers yet to be reported).
The crow deaths have not been confirmed to be due to West
Nile-like virus.
Moreover, even if dead crows are antibody positive, it is not
confirmed that they died of the disease.
We were in northern Westchester last night and actually found
two mosquitos in my parents house. However, the total mosquito
population this summer has been far below normal because of the drought.
Moreover, there have been no human cases of encephalitis in
northern Westchester.
So the widescale pesticide spraying is in response to crows that
have died of still undocumented cause(s). This is not a rational public
health activity.
=========================================================
Now my response:
I wrote "It is not surprising that those interested in lepidoptera
should > be appalled by the broadcast "mosquito control" spraying
programs. > However, we should also make it clear that it is not simply
the relative > value of controlling mosquitos vs preserving all the
non-target species."
Paul responded: Where are the thousands of carcasses of the non-target
species Mike?
My observation: Malathion is NOT mosquito specific. The dead non-target
species have the same status as the dead mosquitos= undocumented.
I understand that there are indeed fewer mosquitos after the
spraying than before the spraying. Whether this is due to the spraying
or represents the natural phenology of mosquitos has not been stated nor
studied. There have been no attempts to survey insects other than
mosquitos.
Paul also wrote: "Millions of people live in New York City. Dozens of
amateur lepidopterists. Hundreds of butterfly enthusiasts.
How come the only report of several dead butterflies comes from a lone
jogger? Is this adequate evidence of a "massive" monarch butterfly kill
in one of the largest metropolitan areas of the world?"
My observation: "There is no further information on dead Monarchs to my
knowledge. This year the NY-NJ area (and perhaps a larger area) has
seen the largest Monarch migration in recent years. I don't think
Monarchs are the issue. Malathion is pretty good at killing adult
Monarchs. Lots of Monarchs would have passed through areas that weren't
sprayed or would have passed before, between, or after spraying, so a
migratory species like the Monarch is probably not important to the West
Nile-pesticide discussion.
I wrote: > There are two issues that should be addressed:
> 1. Risk: someone has alread mentioned that this so-called epidemic
> represents very few cases or deaths.
Paul responded: Risk to what? What non-target organisms of value have
been killed by the Malathion spraying?
My response: This is a very important point. Who studies non-target
species. In this case a non-target species would be anything other than
mosquitos (in fact anything other than Culex).
But more importantly, what does it mean to have non-target
organisms "of value". How would one define non-target species of "no
value".
One implication is that Monarchs have value because they can be bought
and sold.
One would have to be very nihilistic about ecology to assume
that nothing other than Mosquitos (and perhaps Monarchs) have value.
Does value only apply to dollar value (something that can be
bought and sold? This is not what I learned in Ecology 101.
The implication that one would have to define the value of every
species is an argument that has been voiced against preserving
biodiversity per se. David Ehrenfeld argued persuasively that economic
value is the wrong way to approach biodiversity. I agree. Value should
be defined ecologically (certainly a difficult challenge).
My next point> 2. More importantly. The emphasis on broadcast spraying
(which is > likely to be relatively ineffectual)
Paul's response: Ineffectual? If Malathion doesn't adequately kill the
target mosquitoes very well, what basis is there to believe it will kill
significant numbers of non-target insects of value?
Malathion could be completely ineffective against the target mosquitos
if they are already indoors (in the houses where they can bite people at
night). In the Romanian epidemic of West Nile (1996) the presence of
mosquitos indoors, was a major risk factor for infection (time spent
outdoors was also somewhat important).
At the same time malathion could kill non-target species
(including outdoors mosquitos and many other insects). Malathion is
still a pretty good insecticide. So it could be ineffective in
controlling the so-called "epidemic" yet damage non-target species.
I then went on to say that the emphasis on spraying leads people to
ignore the truly > effective ways of preventing themselves from being
bitten by mosquitos > which involve control of breeding places
(elimination or treatment of > standing water), screens, repellent, and
staying away from mosquitos.
Meanwhile, I read that the CDC (the Federal epidemiologic agency which
is the premier infectious disease prevention agency in the world)
recommends the above procedures rather than widescale spraying.
However, CDC wrote that the message for controlling mosquitos locally is
being broadcast on radio and television.
This is certainly true on some stations and channels (the
Westchester Cable channel carried good coverage of how to control
mosquitos in your yard and home). Philadelphia television also had good
coverage (they don't have the virus and arent spraying). However,
network television in New York IS NOT CARRYING THIS INFORMATION. It is
only providing information about spraying and sometimes mentions staying
indoors during spraying.
Paul asked: Have these control measures ever proven to be practical or
truly effective in an urban or other public health setting? Thousands of
New Yorkers can't afford insect repellent let alone a place to live and
sleep that has screened windows.
Yes, these control measures are widely used throughout the
world, especially in urban areas. Some more aggressive measures (like
pouring oil on bodies of water) may not be ecologically desirable,
but are certainly effective. But many countries can't afford to do
frequent spraying for mosquitos, and the efficacy of controlling
mosquitos with spray, has been in question for 40 years.
I was in charge of an infectious disease control program in a
province in Viet Nam and we tried a several approaches to controlling
diseases in refugee camps to control Malaria (mosquito) and Plague (rat
flea).
Aerial spraying with DDT did not reduce rat flea counts (but we
did find some convulsing rats), it did cut down briefly on malaria
dissemination, but had to be repeated. Eliminating mosquito breeding
places was the most effective, followed by dusting of house walls with a
mixture of DDT and talc. We also taught people how to make their own
rat traps out of bamboo (very clever design). They caught lots of rats
that were surveyed for fleas and for plague). Once the villagers got
into it, removing the rats played a significant role in breaking our
plague epidemic. The powers that be stopped authorizing spraying.
To say that thousands of New Yorkers can't afford insect
repellent is not responsive to anything I said. And I doubt that the
mosquito control is being done to protect the homeless people which are
indeed a social and economic problem in New YOrk. If that were the case
we wouldn't see so much spraying in affluent areas of Queens, for
example.
I concluded > 3. The notion that spraying insecticides on a broadcast
basis is innocuous...
The response was:
A bottle of chlorox contains chlorine - a powerful chemical that will
kill almost any living creature undiluted out of the bottle. Yet most of
us have no problem knowing chlorine is in all our tap water - the water
we drink, cook and bathe in and the water we use in our butterfly
gardens. We know from decades of practical experience that the dose
makes the poison in the case of chlorine. Ditto for Malathion.
I would agree with this. As long as malathion is in the bottle, I have
no doubt that it is innocuous. I have a bottle myself which I reserve
for special occasions and use for spot applications. It remains
effective when applied judiciously and infrequently and safe when it
resides in a bottle in my pesticide cabinet. I also take personal
protective precautions when I apply it.
Paul added: After 4-5 decades of mostly successful use in public
health pest control, we know low doses of Malathion broadcast from the
air that are sufficient to kill target dipterans will not harm
significant numbers of non-target insects or other wildlife of value.
I personally don't know that this can be substantiated.
Malathion is a pretty broad spectrum organo-phosphate which in high
doses can effect humans. In our occupational medicine clinic I have
diagnosed humans with excessive exposure to malathion (some might even
call it malathion poisoning) based on lowered cholinesterase levels.
But it is true that the dose that kills vertebrates is higher than the
dose that kills insects. So it should be possible to achieve an
application that kills insects without killing vertebrates.
However, since the vast majority of Dipterans are non-target in
this case, I don't think the statement is correct that it would kill
"target dipterans" without harming significant numbers of non-target
insects. The evidence isn't there.
Paul concluded: Virtually all lepidopterists have years of
practical working experience with chlorine and do not fear it. But very
few have years of experience with Malathion. We fear things we don't
know about. For example, I would be nervous going on a tour of a
nuclear power plant even though I can see hundreds of people working
there safely.
Actually, very few lepidopterists have much experience with
chlorine itself (a highly toxic gas that is one of the main causes of
large scale human evacuations). We do have experience with chlorox, and
don't fear it. Most of us don't fear chlorine in our drinking water (we
don't have it in our well water). I don't think many people fear
malathion either. It's not the fear, but the irrational basis for
applying it that I objected to.
But not to worry, I also visit nuclear power plants (as part of
my job) and recently conducted an inspection tour of a nuclear reactor
that was in the process of being "cocooned" (a neat technical term for
sealing up the core completely to contain the radiation for a period of
at least 75 years).
By using the term "cocoon" the radiation safety specialists
must be thinking that in the next century the radiation will emerge as a
beautiful moth.
Michael Gochfeld
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