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The Homeowners Column
The Buzz on Mosquito Repellants
State Master Gardener Coordinator
What is the most dangerous animal in the world? Perhaps a grizzly bear or a great white shark? It's actually the tiny mosquito. Mosquitoes are responsible for more human illness and death worldwide than any other animal. Mosquitoes spread human diseases such as malaria, dengue fever, yellow fever, encephalitis, and west Nile virus and in animals equine encephalitis and dog heartworm. Malaria kills between 700,000 to 2.7 million people every year.
Fortunately several of these diseases have been virtually eradicated from the U.S. but West Nile Virus, encephalitis and dog heartworm are still a concern. Plus mosquitoes make spending time outside uncomfortable and itchy skin from their bites is not much fun either. The importance of effective mosquito repellants relates to public health and quality of life.
Female mosquitoes (males don't bite) are attracted to large dark objects. They can detect carbon dioxide, heat, moisture and human sweat. Repellants work by blocking the female mosquito's ability to detect us as a meal.
According to U of I extension entomologist Raymond Cloyd, DEET (N, N-diethyl toluamide or N, N-diethyl-meta-toluamide), found in products such as Off® and Cutter® has been the product of choice as a mosquito repellant for many years for its high level of protection and persistence on human skin. In general, DEET has a good safety record except for some individual allergic reactions.
Repellants vary in their concentration of DEET. A 30% concentration provides up to 8 hours of protection. 6% lasts about 2 hours. Apply DEET only to exposed skin areas. DEET is toxic if swallowed. It should not be used on children less than 2 years old and only concentrations of 10% or less should be used on children. DEET is best applied to clothing, but it can harm plastics.
Avon's Skin So Soft® can help repel some mosquitoes but it lasts about 20 minutes.
Permethrin is a pyrethroid-based insecticide applied to clothing or on pretreated clothing sold as Buzz Off®. Permethrin does not repel mosquitoes, but actually kills them on contact. It should only be applied to clothing and not on skin.
According to Cloyd plant essential oils such as clove, peppermint, geranium, and catnip may repel mosquitoes. Citronella, which is derived from a lemon-scented grass (Cymbopogon nardus), is commonly used as a repellent in products such as Natrapel® and Buzz Away®. The oils, however, volatilize rapidly depending on temperature and wind so effects may be short lived. For example, citronella is only active for approximately 30 to 40 minutes.
When using any repellent, don't apply near eyes, on lips, on wounds or broken skin; avoid breathing spray, don't use near food and wash repellent off with soap and water when it's no longer needed. Always read the product label before applying.
According to University of Florida there is no scientific evidence that eating garlic or onions will make a person repellant to mosquitoes; more likely repellant to other people. Repellant wristbands have not been shown to be effective.
Wear light colored, long sleeved shirts and long pants if you will be in mosquito areas. Avoid wearing perfumes. Mosquitoes tend to bite at dawn and dusk, although the Asian tiger mosquito is a voracious feeder during the day.
Adult mosquitoes develop from larvae that live in standing water in ponds, pools, gutters, buckets, barrels and birdbaths. Make sure you are not compounding the mosquito problem in your landscape. Remove old tires, buckets and other water-holding containers. Mosquitoes can breed in containers of water as small as a tin can. Change water in birdbaths at least once a week. In rain barrels or tree holes use mosquito dunks or pellets containing the bacterial agent Bacillus thuringiensis israelensis. Don't let mosquitoes keep you from enjoying your garden.