West Nile virus, water conservation, and your landscape
Posted on Aug 17, 2012 by Michael Parkey
Last night my east Dallas neighborhood received the first aerial spraying for mosquitoes in an attempt to control the West Nile virus outbreak. I took no special precautions, and this morning my chickens, pigeons, doves, and goldfish were all happy, apparently healthy, and eager for breakfast. Of course any possible long-term effects are not visible. I have been waiting for reports from my bee-keeping friends, but the worst predictions of disaster seem to be unfounded. But that does not make me happy about aerial spraying.
Make no mistake, we are in a public health crisis. I will not quote the statistics repeated in every news report, but in my neighborhood of 379 homes, two residents are sick with the virus. These are not statistics, these are my neighbors who live less than a block away. For public health officials, this is a classic “damned if you do, damned if you don’t” scenario.
How did the crisis develop? A warm winter and relatively wet spring created good conditions for mosquitoes. In fact, a mosquito borne West Nile Virus outbreak is almost as predictable as hot weather in the summer here. But we didn’t take any steps to prevent it early in the year. Instead, we neglected the problem until it became a crisis, just like we neglect city infrastructure, air quality, and other public health problems.
When the crisis hits, we then reach for what I call the Texas Big Fix: a spectacular, expensive, inefficient, and rather ineffective solution that arouses great controversy. The “ground assault”, “aerial attack”, “war on West Nile” is a perfect example.
The best way to control mosquitoes is to kill their larva and eliminate their breeding habitat. This is far more effective and safer than ground or aerial spraying, but it requires a sustained, patient, labor-intensive, and skillful effort. It also requires an informed public who is willing to participate. The techniques are well known. Drain all stagnant water, especially that which collects accidentally in normal objects of the urban environment. If the water cannot be drained, treat it with Bacillus thuringiensis israelensis (Bti) or stock it with Gambusia affinis, the native mosquito fish. Send out code inspectors to cite owners of neglected swimming pools. This all takes work, but it is not rocket science. Local governments could hire and train our own citizens to do it, instead of giving the money to out-of-state aerial pesticide application companies.
And stop over-watering your landscape! Early last Wednesday, my neighborhood received about two inches of rain. As I walked one block to a visit a neighbor that same evening, I saw three irrigation systems running! And all of them produced fugitive water that ran down the street and into the storm drain.
Not only is this wasteful and stupid, but I can guarantee that the 60 year old storm sewers in our neighborhood are not working perfectly any more, if they ever did. The soil has moved, pipes have settled and broken, and water stands in them. These are bacteria-rich pools of stagnant water, protected from extremes of temperature, the perfect environment for mosquito larva.
Unlike most public health emergencies, West Nile virus is most prevalent in the richest parts of Dallas County: the Park cities and north Dallas. These are precisely the areas where people habitually over-water their landscapes. Most of us know that mosquitoes lay their eggs in stagnant water. But did you know that adult mosquitoes need shady, humid, wind-free places to rest during the day? And they need fresh, juicy plant growth. Male mosquitoes eat nothing but plant sap and nectar, which they suck from soft plant tissues. Depending on their species, female mosquitoes can subsist on plant sap for a long time, but they need a blood meal in order to lay eggs. That is why they bite us.
Sacramento and Yolo Counties in California have been controlling mosquitoes for many years with aerial spraying. They tell us that they can detect no adverse effects on humans, animals, or the environment. Aerial spraying is probably not the Apocalypse, but it should not be our only solution either. What really frightens me is that when the disease subsides, with or without aerial spraying, we will all go back to sleep. And do nothing about the mosquitoes until next summer, when we will have another outbreak, and reach for the Texas Big Fix again.