[afro-nets] Cinnamon Oil Found Effective in Mosquito Control

[Claudio Schuftan <claudio@hcmc.netnam.vn>]

Cinnamon Oil Found Effective in Mosquito Control
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Cinnamon oil kills mosquitoes

Cinnamon oil shows promise as a great-smelling, environmentally
friendly pesticide, with the ability to kill mosquito larvae,
according to a new study published in the July 14 issue of the
Journal of Agricultural and Food Chemistry, a peer-reviewed
journal of the American Chemical Society, the world's largest
scientific society.

The researchers also expect that cinnamon oil could be a good
mosquito repellant, though they have not yet tested it against
adult mosquitoes.

Besides being a summer nuisance, mosquitoes pose some major pub-
lic health problems, carrying such deadly agents as malaria,
yellow fever and West Nile virus. While conventional pesticide
application is often effective in controlling mosquito larvae
before they hatch, repeated use of these agents has raised seri-
ous environmental and health concerns.

"These problems have highlighted the need for new strategies for
mosquito larval control," says Peter Shang-Tzen Chang, a profes-
sor in the School of Forestry and Resource Conservation at Na-
tional Taiwan University and lead author of the paper. Scien-
tists are increasingly turning to more benign natural chemicals
to ward off mosquitoes and other pests.

Chang and his coworkers tested eleven compounds in cinnamon leaf
oil for their ability to kill emerging larvae of the yellow fe-
ver mosquito, Aedes aegypti. "Four compounds - cinnamaldehyde,
cinnamyl acetate, eugenol and anethole - exhibited the strongest
activity against A. aegypti in 24 hours of testing," Chang says.

Larvicidal activity is judged with a measurement called LC50.
"The LC50 value is the concentration that kills 50 percent of
mosquito larvae in 24 hours," Chang explains. Lower LC50 trans-
lates into higher activity, because it takes a lower concentra-
tion to kill larvae in the same amount of time. All four com-
pounds had LC50 values of less than 50 parts per million (ppm),
with cinnamaldehyde showing the strongest activity at an LC50 of
29 ppm.

Other common essential oils, such as catnip, have shown similar
promise in fighting off mosquitoes, but this is the first time
researchers have demonstrated cinnamon's potential as a safe and
effective pesticide, according to Chang.

Cinnamaldehyde is the main constituent in cinnamon leaf oil and
is used worldwide as a food additive and flavoring agent. A for-
mulation using the compound could be sprayed just like a pesti-
cide, but without the potential for adverse health effects -
plus the added bonus of a pleasant smell.

Bark oil from the Cinnamomum cassia tree is the most common
source of cinnamaldehyde, but the tree used in this study - in-
digenous cinnamon, or Cinnamomum osmophloeum - has been of in-
terest to researchers because the constituents of its leaf oil
are similar to those of C. cassia bark oil. The leaves of C. os-
mophloeum, which grows in Taiwan's natural hardwood forests,
could be a more economical and sustainable source of cinnamon
oil than isolating it from bark, Chang says.

Though the team only tested the oil against the yellow fever
mosquito, cinnamon oil should prove similarly lethal to the lar-
vae of other mosquito species, the researchers say. In further
studies they plan to test cinnamon oil against other types of
mosquitoes as well as different commercial pesticides.

"We think that cinnamon oil might also affect adult mosquitoes
by acting as a repellant," Chang says. The researchers haven't
yet tested this theory, but they plan to find out in the near
future.

The Council of Agriculture of the Executive Yuan, a government
agency in Taiwan, provided support for this research.