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Mosquito control comes with environmental costs

In Everglades National Park, where spraying pesticides is banned, one unprotected human can be a walking blood-meal buffet for as many as 500 mosquitoes per minute.

And how many bites does it take to ruin a poolside barbecue, or at least generate the average complaint to a mosquito control department? Precisely 1.3 per minute, said University of Florida entomologist Jonathan Day.

So you can see how tough it would be to market the state as a sunny paradise — or even as inhabitable — without mosquito control.

"It's pretty well established that the things that allowed for the development of Florida are air conditioning, interstate highways and mosquito control," Day said.

And though comfort and property values are mainly what these spraying programs are all about — and have been since the first one was established in Indian River County in 1924 — there are also West Nile virus, dengue and several other mosquito-borne illnesses to consider.

"If one or two people get sick from the disease that these carry, we'll be in a world of hurt," County Commission Chairman John Druzbick said at Tuesday's meeting.

He was responding to a report from county environmental services director Joe Stapf, who explained how the county responded to the 850 complaints from residents about the early start to mosquito season in Hernando County.

We got a few rainy days in late March, millions of adult mosquitoes emerged from the larval stage into the adult, biting stage, and by the end of last week the county had responded by spraying 225 gallons of pesticides from Ridge Manor to Hernando Beach.

The extra weeks of spraying are expected to require the return of almost all of the $102,000 removed from mosquito control's budget last year. So, it costs us, this expectation that we should be bug-free even in Florida.

This slight note of sarcasm is not to suggest, of course, that we should do away with mosquito control. It just seems like a good time to point out that every human convenience and comfort comes with an environmental cost. And, if you think about it, the ultimate — and unattainable — goal of mosquito control is pretty extreme: wiping out the bottom link of the food chain.

For example, mosquito larvae are one of the main food sources for hatchlings in our estuaries.

Less larvae mean fewer of these small fish, fewer of the medium fish that feed on them and ultimately fewer tarpon and snook.

Then there's permethrin and other pesticides from the same family that are the main chemicals the county sprays. These neurotoxins are generally less effective as body temperatures climb.

That means they have very little impact on most mammals (other than, for some reason, cats), which makes them a big improvement on malathion, which the county used until a few years ago. But that also means that they can be highly toxic to frogs, fish and other cold-blooded aquatic life, although Guangye Hu, the county's mosquito control supervisor, said he has never received a report of fish or amphibian die-offs from spraying.

And, being insecticides, obviously, permethrin is hard on honeybees, fireflies and butterflies.

If you think you see fewer fireflies than you did when you could collect a jar full, no problem, on a summer evening as a kid, well, that's a fact. They are in decline worldwide. Light pollution is probably the main culprit; it's hard for the female to be excited by a male's blinking abdomen when it's competing with a 7-Eleven sign. But agricultural and residential spraying certainly doesn't help, said Jerry Hayes, the state's chief of apiary inspection.

"Any insect that comes in contact with (permethrin) is going to be impacted," he said.

Maybe you've seen a hive of honeybees in a crawl space recently and been reassured that, despite what you've heard, the species is doing fine. Not so, Hayes said. The bees in your yard are almost certainly the hardier, more aggressive Africanized varieties.

Feral populations of the benign European bees have been almost wiped out in Florida, and insecticides have definitely played a part, he said.

The situation with butterflies is more complicated, said Mark Minno, who has written several books on the subject. Exotic ants and wasps appear to be the main culprit in the statewide decline, and in some isolated cases spraying for mosquitoes appears to have helped imperiled butterfly populations; it tends to kill these predators.

Still, there are fewer butterflies in Florida than there once were, and insecticides are one reason why.

If we can't stop spraying, then what can we do?

Well, the more you learn about mosquito control, the more you are likely to be impressed.

That 225 gallons is not much, considering the miles the spraying trucks cover, Stapf said. That's because their drivers release tiny amounts for each mile covered.

Mosquito control workers also have a lot of ways to kill larvae, most of them nontoxic and highly targeted. These include introducing gambusia (mosquitofish) to infested water, injecting the water with bacteria that feed only on mosquito larvae, and suffocating these populations with natural oils that cover the surface.

And then there's the low-tech practice of just dumping out the many isolated pools of water — in tires, children's toys, neglected bird baths — where the larvae are unlikely to boost the food chain and very likely to make our lives miserable.

So, that's one suggestion before you call mosquito control: That brown water languishing somewhere in a corner of your yard? Just dump it out.

Mosquito control comes with environmental costs 04/28/11 [Last modified: Friday, April 29, 2011 5:12pm]
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