Scientific Research Findings
In research conducted at Iowa State University, it was found that natural oils including catnip were 10 times more effective at repelling mosquitoes than the compound used in mist commercial bug repellents.
The finding was reported at the 222nd Anual Meeting of the American Chemical Society in Chicago. Chris Peterson and Joel Coates studied the effect of nepetalactone on mosquitoes.
Nepetalactone is an essential oil in catnip that gives the plant its odor.In past studies, the researchers had found that catnip oils could repel cockroaches. Peterson recently left a post-doctoral research position at Iowa State University and is now working as an entomologist with the U.S. Forestry Service in Starkville, Mississippi. Joel Coates is the Chair of ISU's Department of Entomology.
The researchers placed a group of 20 mosquitoes in a glass tube treated on one side with a huge dose of nepetalactone. After 10 minutes, an average of 80% of the mosquitoes had moved to the untreated side of the test tube. In a low dose test, an average of 75% had moved to the untreated side.
The researchers conducted similar tests with DEET (Diethyl-Meto-Toulamide), the compound used in many commercial repellents. In those tests 55% to 60% of the insects moved away from the treated side.
In the laboratory, repellency is measured on a scale from 100% (all mosquitoes repelled) to -100% (all mosquitoes attracted). In the ISU tests, catnip ratings ranged from 49% to 59% at high doses, and 39% to 49% in low doses.
Peterson said that it took about one tenth as much nepetalactone to have the same repellency DEET. "In other words, nepetalactone is about ten times more effective than DEET," he said.
"Most commercial insect repellents contain about 5-10% DEET. Presumably, much lass catnip oil would be needed to achieve the same repellency as a DEET based repellent."
