New potential mosquito repellent better than DEET

IVAN

Catnip Repels Mosquitoes More Effectively
Than DEET


CHICAGO, August 27 Researchers report that nepetalactone,
the essential oil in catnip that gives the plant its characteristic
odor, is about ten times more effective at repelling mosquitoes
than DEET the compound used in most commercial insect
repellents.

The finding was reported today at the 222nd national meeting
of the American Chemical Society, the world s largest scientific
society, by the same Iowa State University research group that
two years ago discovered that catnip also repels ****roaches.

Entomologist Chris Peterson, Ph.D., with Joel Coats, Ph.D.,
chair of the university s entomology department, led the effort
to test catnip s ability to repel mosquitoes. Peterson, a former
post-doctoral research associate at the school, is now with the
U.S. Department of Agriculture Forest Service, Wood Products
Insects Research Unit, in Starkville, Miss.

While they used so-called yellow fever mosquitoes (Aedes
aegypti) one of several species of mosquitoes found in the
United States Peterson says catnip should work against all types
of mosquitoes.

Aedes aegypti, which can carry the yellow fever virus from one
host to another, is found in most parts of the United States.
Yellow fever itself, however, only occurs in Africa and South
America, according to the Centers for Disease Control.
Vaccines and mosquito control programs have essentially wiped
out the disease in the United States, although there have been
isolated reports of unvaccinated travelers returning with the
disease. The last reported outbreak in this country was in 1905.

Peterson put groups of 20 mosquitoes in a two-foot glass tube,
half of which was treated with nepetalactone. After 10
minutes, only an average of 20 percent about four mosquitoes
remained on the side of the tube treated with a high dose (1.0
percent) of the oil. In the low-dose test (0.1 percent) with
nepetalactone, an average of 25 percent five mosquitoes
stayed on the treated side. The same tests with DEET
(diethyl-m-toluamide) resulted in approximately 40 percent
to 45 percent eight-nine mosquitoes remaining on the treated
side.

In the laboratory, repellency is measured on a scale ranging
from +100 percent, considered highly repellent, to 100 percent,
considered a strong attractant. A compound with a +100
percent repellency rating would repel all mosquitoes, while 100
percent would attract them all. A rating of zero means half of
the insects would stay on the treated side and half on the
untreated side. In Peterson s tests, catnip ranged from +49
percent to +59 percent at high doses, and +39 percent to +53
percent at low doses. By comparison, at the same doses, DEET s
repellency was only about +10 percent in this bioassay, he notes.

Peterson says nepetalactone is about 10 times more effective
than DEET because it takes about one-tenth as much
nepetalactone as DEET to have the same effect. Most
commercial insect repellents contain about 5 percent to 25
percent DEET. Presumably, much less catnip oil would be
needed in a formulation to have the same level of repellency as
a DEET-based repellent.

Why catnip repels mosquitoes is still a mystery, says Peterson. It
might simply be acting as an irritant or they don t like the smell.
But nobody really knows why insect repellents work.

No animal or human tests are yet scheduled for nepetalactone,
although Peterson is hopeful that will take place in the future.

If subsequent testing shows nepetalactone is safe for people,
Peterson thinks it would not be too difficult to commercialize it
as an insect repellent. Extracting nepetalactone oil from catnip
is fairly easily, he says. Any high school science lab would have
the equipment to distill this, and on the industrial scale it s quite
easy.

Catnip is a perennial herb belonging to the mint family and
grows wild in most parts of the United States, although it also is
cultivated for commercial use. Catnip is native to Europe and
was introduced to this country in the late 18th century. It is
primarily known for the stimulating effect it has on cats,
although some people use the leaves in tea, as a meat tenderizer
and even as a folk treatment for fevers, colds, cramps and
migraines.

A patent application for the use of catnip compounds as insect
repellents was submitted last year by the Iowa State University
Research Foundation. Funding for the research was from the
Iowa Agriculture Experiment Station.

Chris Peterson, Ph.D., is a former post-doctoral research
associate at Iowa State University in Ames, Iowa, and is now a
Research Entomologist with the U.S. Department of
Agriculture Forest Service, Wood Products Insect Research
Service, in Starkville, Miss.

Joel R. Coats, Ph.D., is professor of entomology and toxicology
and Chair of the Department of Entomology at Iowa State
University in Ames, Iowa.




Note: This story has been adapted from a news release issued by American
Chemical Society for journalists and other members of the public. If you wish to
quote from any part of this story, please credit American Chemical Society as the
original source. You may also wish to include the following link in any citation:
http://www.sciencedaily.com/releases...0828075659.htm




There are also existing products with geraniol, check:
http://news.ifas.ufl.edu/print/1999/99_0629a.html

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