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Photo: Mosquito Aedes aegypti.
ARS scientists and their collaborators in a company called Agro Research, Inc., are working to identify the active ingredients of a mosquito- and ant-repelling essential oil that comes from a native American Samoan plant. Photo courtesy of Jessica Lawrence, NC State Entomology Dept.,

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Plant Essential Oil Eyed as Mosquito, Ant Repellent

By Sharon Durham
August 24, 2009

Agricultural Research Service (ARS) scientists have teamed up with researchers from a company in American Samoa to investigate the chemical makeup of a mosquito- and ant-repellent essential oil from a native Samoan plant.

The ARS scientists and researchers at Agro Research, Inc., in Pago Pago, American Samoa, discovered that the oil from a local plant repelled mosquitoes and pest ants in preliminary studies, which were conducted under a material transfer agreement. The isolation and identification of the active component (or components) will be done as part of a recently established one-year cooperative research and development agreement.

The plant is one of the 540 native species of flowering plants in American Samoa, a U.S. island territory in the South Pacific.

ARS chemists Robert Vander Meer and Ulrich Bernier at the agency’s Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Fla., are working with Agro Research, Inc.’s Pemerika Tauiliili to identify the active ingredients in the plant essential oil.

Two mosquito species—Aedes aegypti and Anopheles albimanus—were used to evaluate the essential oil’s repellency. A. aegypti transmits viruses that cause yellow fever, dengue and chikungunya. A. albimanus transmits malaria parasites and is not as susceptible to repellents as many other mosquito species.

The essential oil was also tested on the red imported fire ant, Solenopsis invicta. Significant repellency was observed with concentrations diluted more than 100-fold, and the active components are likely a small fraction of the total oil.

While American Samoa is malaria-free, mosquitoes pose significant problems for the Samoan population due to transmission of dengue virus.

Exploration for new active ingredients among botanical extracts has value because it can lead to the discovery of new synthetic analogs with unique and useful properties.

ARS is the principal intramural scientific research agency in the U.S. Department of Agriculture.