Using bug spray, bait and other household pesticides to prevent ant invasions is futile, according to a new study by Stanford researchers to be published in the journal American Midland Naturalist.
``People spend a lot of money on year-round pesticides,`` says Deborah M. Gordon, associate professor of biological sciences and lead author of the study, ``but it`s not the pesticide that keeps ants out of your home, it`s the weather.``
Gordon, who received a Guggenheim Fellowship earlier this month in recognition of her research on ant behavior, is author of the book Ants at Work: How Insect Society Is Organized.
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.
Rain and drought
The Stanford study is the first to examine a phenomenon Californians have long suspected: that the majority of Argentine ant invasions occur during winter rainstorms and summer droughts.
``Our goal was to determine if there really is an association between ant invasions and weather,`` says Gordon, ``and if so, does pesticide use affect the intensity of infestation.``
To find out, the Stanford team surveyed 69 households in the heart of California`s Silicon Valley - from Redwood City to Gilroy - between January 1998 and July 1999. Each week, participants were asked to estimate how many ants invaded their home and whether pesticides were used to control the invaders. Gordon and her co-workers also collected weekly temperature and
Contact: Mark Shwartz