Column: L.A. area’s mosquito dilemma: Use pesticides or suffer through the summer plague

Close up of a mosquito in profile
The number of mosquitoes in the Los Angeles area has risen dramatically in recent years.
(Associated Press )

A year ago, I wrote a column bemoaning the arrival of mosquitoes in Los Angeles.

I was shocked by their sudden appearance in a city where I’d always been able to sit outside, where I was in the habit of leaving doors and windows open and where I’d never once been bitten.

I quoted old Los Angeles Times stories from throughout the 20th century boasting that the region didn’t have them. For instance, a story from August 1915 said: “The winged swordsman of summer is not, except in a few disfavored localities, to be found within this city.”

Yeah, well, those days are over, I wrote.

A year later, the situation is even more depressing. The “winged swordsman” — which is far too kind and poetic a name for this vicious predator — is no longer a shocking new phenomenon in Southern California. Now, sadly, it’s routine. Normal.

For a while last summer, I tried to fend off the ferocious little buggers by slathering myself in bug spray. It smelled, it was sticky, but it kept them away for a little while. Some of the repellent I used contained the chemical DEET, which I’d always heard could be dangerous. It’s the most effective repellent, by most accounts — but I worried every time I put it on.

Then a few weeks ago I bought a device that promised to create a mosquito-free area within a 15-foot radius. It’s a little black box; you push a button and an insecticide mist comes out. The active ingredient is allethrin, a synthetic compound. It’s odorless and it works moderately well so far, but it too makes me nervous as I sit within its circle.

I faced a dilemma. Was I putting my health in jeopardy to avoid some bug bites? Was I right to choose insecticides over insects? Was I being irresponsible?

The history of pesticides in this country is not pretty. Even if we haven’t read it, many of us are aware of “Silent Spring,” the book by Rachel Carson that awakened the world in 1962 to the dangers of the indiscriminate use of pesticides and led to the banning of DDT.


So I called Susanne Kluh, director of scientific and technical services at the Greater Los Angeles County Vector Control District. She started out by telling me, as others have, that the best way to control mosquitoes is to stop them from breeding in the first place by doing away with any standing water on your property — including small amounts in clogged roof gutters or flowerpots or buckets.

OK, but I’ve tried that, and it hasn’t worked. Maybe they’re breeding in someone else’s backyard.

But Kluh also told me that insect repellent isn’t really dangerous if you use it as directed, even if it contains DEET. There have been enormous amounts of research into DEET, which many consumers have been loath to use but which has been deemed safe over and over. The Centers for Disease Control and Prevention agrees that DEET is safe, especially if you keep it out of the hands of children, don’t spray it into your eyes and — listen up, fools — don’t drink it. The U.S. Environmental Protection Agency adds that, used appropriately, DEET isn’t likely to have adverse affects on “terrestrial life or aquatic organisms.”

As for allethrin, Kluh’s not a big fan of the use of residual pesticides — but not because they’re harmful to humans. Her concern is that if they’re used incorrectly, overuse and low-dose exposure could lead to resistance in mosquitoes, rendering the insecticides useless in the long term. That’d be counterproductive.

Besides, as I have to keep reminding myself when I worry about using pesticides, mosquitoes aren’t just irritants. Bill Gates once called them the most dangerous human predators in the world — which sounds like a joke when you think of lions and tigers and bears, until you reflect on it.

Mosquito-borne malaria still kills hundreds of thousands of people each year. Some believe mosquitoes have killed more humans than anything else in history.

Lions, tigers and bears can’t compete.

So insecticides serve a purpose beyond just helping us avoid itchy bites.

In Southern California today, the most worrisome mosquito-carried disease is West Nile virus, carried by Culex mosquitoes, which arrived in the region in 2003. I knew a woman who died of West Nile after being bitten by a mosquito in the Beverly-Fairfax neighborhood. This disease is no joke. Each year, 150 to 300 people in L.A. County are found to be infected with West Nile. But many more cases likely go undetected, since symptoms are often mild enough that people don’t seek medical help.

Additionally, the more recently arrived Aedes species of mosquitoes is able to carry and spread dengue fever, Zika, chikungunya and other diseases. Those dangerous diseases haven’t appeared here yet, but if a person returns from a trip infected with one of them and gets bitten here by an Aedes mosquito, it could spread.

The cases of diseases spread by mosquito, tick and flea bites more than tripled across the country between 2004 and 2018, according to the CDC.

For the record, the villain in all this is more of a winged swordswoman than a swordsman, since only female mosquitoes bite (seeking the blood they need to produce their eggs).

The way it works is that she pierces your skin with the pointy tip of her proboscis, searching for a blood vessel. She then sucks out your blood while injecting saliva that contains an anti-coagulant (which causes the itch). If she’s infected with a virus, it can be passed to you through her saliva.

Gross, right?

Meanwhile, Kluh and others are investigating other options, including releasing masses of male mosquitoes into the wild that have been infected with a particular bacterium. The sperm of the bacterium-infected males causes “cytoplasmic incompatibility” — so that any eggs that are laid do not hatch. It’s insect birth control, if you will, that reduces the population over time.

Welcome to Sci Fi 101. I hope it works.