sealPurdue News

May 22, 2002

For mosquito protection, repellents are best, devices don't work

WEST LAFAYETTE, Ind. – If you don't want to be covered with mosquito bites, a Purdue University entomologist suggests using a good repellent and skipping expensive devices advertised to eliminate the blood-sucking insect.

"A lot of gadgets claim they control mosquito populations, but none have proven effective," said Ralph Williams, Purdue entomology professor. This includes "bug zappers," the plug-in lights that lure insects and then kill them when they touch an electric grill.

Of all the ways touted for keeping mosquitoes at bay, the best are eliminating their breeding areas and using a spray or lotion that drives the pesky creatures away, Williams said.

Only use a repellent that is Environmental Protection Agency-registered; you can find the registration number on the container, he said. The best repellents have diethyl-meta-toluamide (DEET). For children, only use products specifically labeled for their use. It's also important to follow the instructions found on the repellent container because some can be used on the skin while others are only for use on clothes.

The clothes you wear also can help deter mosquitoes, Williams said. Light colored clothing with long sleeves and long pants provide the best protection. Williams also suggests dumping or draining standing water, which acts as a mosquito breeding ground.

These methods are far superior to fancy, ineffective equipment, he said.

"Research studies have been done at Notre Dame University that show that the bug zappers don't reduce mosquito biting or the population," Williams said. "They will kill a lot of insects but actually may make your mosquito problem worse."

This is because the light lures mosquitoes that otherwise might not come near your property, and the swarms it attracts are far more than the light device will kill, he said.

Even a worse bet for ridding your property of the pest are ultrasonic gadgets. Not only don't they deter or kill mosquitoes, they won't chase away rodents or any other vermin, Williams said. In addition, Indiana has made over-the-counter sales of these devices illegal. However, many people still are buying them through phone and Internet orders, he said.

Williams said the state registers devices that can back up the claims they make in connection with insect or animal control.

Other methods of eliminating mosquitoes also have not been supported by studies.

"There is no evidence that spreading garlic juice or planting certain flowers, or "mosquito plants," will have any effect in controlling mosquitoes," Williams said.

Candles with citronella can be helpful, he said, but where they're placed and the size will determine how much protection they provide. In addition, the candles obviously won't be helpful in windy conditions.

One new device that shows promise in mosquito control uses carbon dioxide to attract the bugs, Williams said. It's successful because mosquitoes are drawn to sources of blood by odors, including perspiration and the carbon dioxide expelled by mammals when they breathe.

Though there are insecticides made specifically for use on mosquito larvae, Williams said homeowners should have someone trained in mosquito control, such as health department personnel, apply them. Homeowners don't usually know and understand the mosquito life cycle or recognize mosquito larvae well enough to use these insecticides, he said.

Writer: Susan A. Steeves, (765) 447-6566,

Source: Ralph Williams, (765) 494-4560

Ag Communications: (765) 494-2722; Beth Forbes,;

Related Web sites:
Purdue Extension resources for West Nile virus
Animal and Plant Health Inspection Service
Indiana Department of Health
Centers for Disease Control and Prevention

Purdue News Service: (765) 494-2096;

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