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Daily News Archive
From May 7, 2001

Study Proves Pesticides Ineffective Against Ant Infestations

According to a new study by Stanford researchers to be published in the journal American Midland Naturalist, using bug sprays, baits and other household pesticides to prevent ant invasions is futile. "People spend a lot of money on year-round pesticides," Deborah M. Gordon, associate professor of biological sciences and lead author of the study told the Stanford Report, "but it's not the pesticide that keeps ants out of your home, it's the weather."

Dr. Gordon, an ant expert who recently received a Guggenheim Fellowship earlier this month in recognition of her research on ant behavior, focused her study on the Argentine ant, which routinely invades homes and apartments throughout California during periods of rainy weather and drought. She and her colleagues based their pesticide study on an 18-month survey of homes and apartments in the greater San Francisco Bay Area, a region plagued by the Argentine ant (Linepithema humile) -- an invasive South American species introduced into California nearly a century ago. Lacking natural enemies, Argentine ants have taken over large areas of the state, wiping out native ant species and routinely invading human households. The aggressive insect also has become a major pest in other parts of the world with mild winters -- including Hawaii, South Africa, Australia and the French Riviera.

To control infestations, participants in the study reported using a variety of ant killers including: pesticide sprays, such as Raid, Black Flag and Hot Shot; baits and traps, including Combat, Grant's and Ortho Ant Kill; cleansers, such as bleach, ammonia, soap, Windex and Formula 409; and herbal and natural products, including hot pepper, chili oil, lemon and vinegar. Nothing worked. "The most reliable cause of a decline in infestation may be a change in the weather. They come in because of the weather, and they go out because of the weather," Dr. Gordon concludes. "By putting out ant killers when there's no infestation, we're only harming ourselves."