To spray or not to spray?

I've talked about pesticides before, mostly in regard to gardening.  The question of how to minimize loss to pests (bugs, disease, animals) is one that those interested in growing food struggle with regularly.  What constitutes "safe" or "organic" practice?  Am I at the mercy of the caterpillars, aphids, and grasshoppers?  As Jeff Gillman points out in The Truth About Organic Gardening, the answer isn't so black-and-white.  The question isn't really, "Is this okay?" But really, "Do the benefits outweigh the risks?"  Unfortunately, the risks may not always be so clear, on either side.

We had a fairly mild winter, with only one or two very short freezes.  Long enough to kill some of my veggies, but not enough to kill off the weeds...or the bugs.  That, coupled with a relatively wet spring, as resulted in a local boon in the mosquito population.  Mosquitoes a la wiki

Mosquitoes have long been trouble (literally, tens of millions of years!) - besides being a nuisance, they are one of the "best" spreaders of some dangerous pathogens.  They have been responsible for the spread of all sorts of diseases: malaria, yellow fever, dengue fever, and West Nile virus, among others.  It's the last that brings me to write.

According to the CDC, and as of 14 Aug, 2012 has seen more cases of West Nile in the US to date than any other year since it was first reported in 1999.  About 50% of those have been in Texas, and most of those have been in the Dallas-Fort Worth metroplex.  By the CDC numbers, Dallas County alone has had 114 of the 693 reported cases this year.  In Texas, 17 have died from the disease this year.  Texas Department of Health statistics

What those numbers suggest is that there's a bit of a public health crisis in DFW.  We're in the middle of August - almost to the height of mosquito activity.  In other words, the culprits will be hanging around for a while.  So, the local governments, Offices of Public Health, and CDC have gotten involved.

Some communities (including my own) have started local pesticide spraying programs.  Trucks drive around with foggers in the late evening, when most people and animals should be inside.  It's targeted - focused on areas with positive mosquito pools and confirmed human cases.  The local governments have declared an emergency and several, most notably Dallas County, are moving to approve aerial spraying which can start as early as tomorrow night.  It's a huge decision; mass spraying has not been used in the metroplex for over a decade.

Critics, though, point to "natural" or "safer" methods of controlling the mosquito population.  They raise concern about the safety of the sprayed pesticides.  (And, I'll had that asking these questions is good.  But here is where we must get past the black & white "chemicals are bad" mindset and look at the whole issue.)  Some neighboring cities, like Fort Worth, had not moved toward pesticide spraying as quickly as other municipalities, and critics pointed toward them as an example of a more conservative approach that focused on public outreach and education.  (In the past day or two, Fort Worth has announced the commencement of limited spraying, though.)

The CDC's protocol for mosquito outbreaks is clear and available online.  And spraying is, if you will, the next step, when larvacide and area control don't seem to be enough.  The CDC recognizes that there will likely be public resistance:

"Wide-area pesticide use is controversial in some communities. As the Environmental Protection Agency indicates, “no pesticide is 100% safe and care must be exercised in the use of any pesticide.”...Studies by the EPA, Karpati, et al.; Currier, M, et al.; and Peterson, et al. support the idea that the benefits of controlling the spread of vectors with pesticides, when conducted according to the directions on the label, outweigh the risks of potential harmful health effects from pesticide spraying...Mosquito control programs can use these [town hall] meetings to discuss how the relative health risk of pesticide spraying is considerably lower than the risks posed by many mosquito-borne diseases such as West Nile virus."

The debate/battle is a question of immediate public health risk versus long-term and environmental concerns.  Of course, these pesticides are not so specific as to only target mosquitoes.  The spray in question, pyrethroid, is toxic to aquatic organisms and bees.  It warns against being used on agricultural land.  But, it's also approved by the EPA for exactly this purpose - public health.

It is important to note that one time spraying does not eliminate the threat.  Only those mosquitoes that come in contact with the spray will be killed.  Typically, multiple applications are required.  And adult mosquitoes are only a portion of the problem - continued larvacide application and removal of breeding area is necessary to prevent more mosquitoes from hatching.

Education is an important first step (and one that has certainly been in the media the past few weeks).  It's not practical to tell people to avoid mosquitoes altogether, so instead, authorities are adivising the public to:

• Use insect repellents containing DEET, picaridin, or oil of lemon eucalyptus.  (MJ and I acquired some for our home a few weeks ago.)
• Wear long pants and long sleeves outside.  (A challenge when it's 100+ after 7 pm!)
• Avoid being outdoors when mosquitoes are most active at dusk and dawn.
• Drain standing water.  This is the breeding ground for mosquitoes.

"The mere implementation of risk communication messages does not mean that the public will immediately accept the program’s advice. The target audience must also see the recommended actions as practical and feasible. The public must also believe that the risk is substantial enough to take action. Several West Nile virus studies suggest that many people who ignore advice to wear repellent or adopt other preventive measures do so because they do not perceive the risk of contracting mosquito-borne disease to be high enough to warrant such actions. People most often report they believe their time of exposure is too short for them to be bitten or that repellents are inconvenient as reasons for non-use of repellent." -Before the Storm, CDC

So there is personal responsibility at play.  There's another complication, as well.  Mosquitoes have wings, so simply ignoring the insect does not solve the issue.  While there is a certain concentration to the current reported cases, there's also some evidence that the affected area is increasing, with central Texas reporting some cases as well.  Containment is needed.  Sometimes you need a really big hammer to stop the escalation.  And perhaps, if there ever was a time to consider wide-use pesticide, this is the sort of time that merits it.

What do you think?

More reading:
Dallas Morning News editorial, 9 August 2012
The spray program
Editorial on risks of West Nile virus
Fort Worth starts spraying (Includes interesting statistics on who has been infected)