Keeping Roaches at Bay

Researchers have confirmed an old wives' tale: placing catnip around the house helps keep cockroaches away.

Iowa State University researchers Chris Peterson and Joel Coats, Ph.D., reported that cockroaches are repelled by catnip - specifically, two forms of the chemical called nepetalactone, found in the catnip plant. Their findings could lead to the development of new natural insect repellents that could be sprayed along baseboards to keep roaches from coming out of the walls.

"There are really no commercial cockroach repellents," said Peterson. "Most are insecticides designed to kill roaches. People don't seem to just want them to go away, they want them dead."

Peterson, a graduate research assistant in the school's department of entomology, also tested osage orange, commonly known as hedgeapple. The inedible softball-sized fruit has long been touted in folklore for its ability to repel "cockroaches, spiders, mice, flies, crickets or just about anything people care to repel," he says.

His study identified the compounds in hedgeapples that repel insects. More work is needed to identify the active agents.

German cockroaches, which are about the size of crickets and common in many parts of the United States, were the only insects studied. Studies of mosquitoes are underway. As yet, there are no plans to examine the effects of catnip and hedgeapple on American cockroaches, though Peterson suspects they would respond the same way as their German cousins.

The Iowa State researchers also confirmed an earlier study's finding that male cockroaches seem to be more sensitive than females to the repellent activity of catnip and hedgeapples. "Why that is, nobody has even offered a guess at this point," Peterson said.

*An American Chemistry Society release.