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Science Column: Mosquito Control

I may be indulging in wishful thinking, but it’s been so warm this week I may surely be forgiven for hoping that spring is finally here. The only downside to that is that in Saskatchewan, snow season is followed promptly by mosquito season.

Fortunately, mosquito control techniques continue to advance, as the recent American Mosquito Control Association conference in Savannah, Georgia, demonstrated.

Mosquito control begins with source reduction–getting rid of the standing water in which mosquitoes breed. This can range from major drainage projects to emptying out that old bucket beside your garage.

It’s impossible to eliminate all standing water, so the next step is trying to prevent any mosquito larvae that might hatch from developing into adult mosquitoes. Options include both biological control (placing mosquito-eating fish, invertebrate predators, parasites or diseases into ditches and ponds) and chemical larvicides.

Adult mosquitoes are harder to deal with. For individuals, the first line of defense is repellent, and test after test confirms that the best repellents are those that contain the chemical DEET. The most popular area repellent is oil of citronella, usually produced by burning candles, torches or coils–all of which are only effective under windless conditions, which alas are somewhat rare in Saskatchewan.

Some people use mosquito traps, such as the popular “insect electrocutor” (better known as the bug zapper). There’s little scientific proof that they’re effective, and one recent study indicated that every time an insect is zapped, it releases a cloud of bacteria–so don’t put the bug zapper right over the picnic table, at least not if you invite me.

Another type of mosquito trap releases a plume of carbon dioxide, heat and moisture, mimicking the breath of a mammal, sometimes combined with a chemical attractant. When the insects approach, they’re sucked up by a vacuum-cleaner-like device. Again, there’s not much scientific evidence that this really helps.

Both inside and outside the house, chemical sprays can be used to kill mosquitoes. Household sprays available now are so quick and effective that very little pesticide is actually released. Of course, your mosquito problem is only solved until a new batch of the pests find their way in through open doors, loose-fitting windows, holes in screens, etc.

Outside, much greater quantities of pesticide can be applied using foggers, but again, this only provides a temporary relief–there’s always another batch of mosquitoes waiting to hatch or simply to be blown in from beyond the area that’s been fogged.

Among the new developments highlighted at the American Mosquito Control Association convention was the Larvasonic, which uses pulses of sound to kill mosquito larva growing in standing water. Resembling a rubber pickle, the Larvasonic was developed by Herb Nyborg from a prototype created by his then-15-year-old son, Michael, as a 2001 science fair project. Nyborg started marketing a professional $4,500 (U.S.) version of the device last year; now he’s trying to find investors to develop a cheaper model for home use.

Also on display was the Anileator, a $246 pesticide sprayer with triple-spray nozzles that break pesticides into microscopic particles that hang around in the air longer. Until now, that technology has mostly been used only by professionals; but due to West Nile Virus, Curtis Dyna-Fog of Indiana, which produces the Anileator, sold 600 of them last year to homeowners.

Similarly, larvicides have traditionally been applied only by professionals, but Wellmark International of Illinois last year began selling $10 bottles of its Pre-Strike mosquito larvicide through Wal-Mart.

Professionals have new tools too, though. For example, there’s a new device that uses the global positioning system to tell the pilots of pesticide-spraying airplanes precisely where the wind will blow the chemicals, so they can change course as necessary. Another system, for truck-mounted sprayers, links computers with radar guns to automatically adjust how much pesticide gets sprayed, based on the truck’s speed.

But for all the new demand for mosquito control–in the U.S., one estimate is that the market for mosquito control products has increased 25 percent due to West Nile Virus–the simplest and best method of reducing the problem still comes down to eliminating standing water.

It’s a message you can bet we’ll be hearing from our own civic governments in the near future… assuming, of course, that spring really is just around the corner.

Mosquitoes and all, here’s hoping!

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