April 24, 2003
AMES, Iowa — Iowa State University researchers have begun testing catnip oil as a possible repellent against mosquitoes carrying the West Nile Virus. Joel Coats, an Iowa State entomologist, began investigating the idea of using catnip oil as a mosquito repellent five years ago with Chris Peterson, a former graduate student. The researchers found that catnip oil repels mosquitoes significantly better than the compound used in most commercial bug repellents. Nepetalactone, the primary active ingredient in catnip oil, was recently patented by ISU. "Consumers are developing some concern about traditional bug sprays. They seem to be looking for alternatives and believe that natural alternatives may be safer," Coats said. Gretchen Schultz, an Iowa State entomology graduate student, is now working with Coats to test nepetalactone's effectiveness against the mosquito species that carries West Nile Virus. The virus can cause fatal encephalitis in humans and horses, and can kill certain domestic and wild birds. The researchers also are conducting tests to compare the repellency of catnip oil to DEET (diethyl-meta-toluamide), the compound used in many commercial repellents. In laboratory tests, the nepetalactone repelled more mosquitoes at lower concentrations. When tested on cockroaches, the repellency of catnip oil didn't last as long as the DEET. Schultz and Coats are currently testing the repellency time of catnip oil against mosquitoes. "We've begun testing on the species of mosquito that transmits West Nile Virus," Coats said. "We also are studying how long catnip oil will protect against mosquitoes. That seems to be the big issue at this time." Catnip is primarily known for its stimulating effect on cats, although some people use the leaves in tea, as a meat tenderizer and as a folk treatment for fevers, colds, cramps and migraines. The catnip plant is a perennial herb in the mint family and grows wild in most parts of the United States. Coats warns that pure catnip oil is too strong to put directly on skin. The doses tested in his laboratory only contain one to five percent of the essential oil. No human testing is planned at Iowa State.