Subscribe to our free daily newsletters
. Earth Science News .




Subscribe to our free daily newsletters



Water Found To Be Main Culprit In Argentine Ant Invasions

Argentine ants tend scale insects. Photo by Marc Dantzker.
by Staff Writers
San Diego CA (SPX) Apr 05, 2006
According to a study conducted by two biologists at the University of California, San Diego, Argentine ants in Southern California need wet soil to live and breed. So residents plagued by indoor infestations of the pesky little critters may find relief by simply shutting off or substantially limiting the use of their outdoor irrigation.

The scientists report in the March 30 issue of the Journal of Animal Ecology that they were able within a matter of weeks to increase the abundance and encourage the spread of Argentine ant ants by irrigating normally dry land. Once irrigation ended and soil moisture declined, the researchers found, the number of ants returned to pre-irrigation levels.

Biologists have long suspected that water is critical to the survival of the tiny ants, which thrive in coastal California and invade new subdivisions that have transformed much of Southern California's arid landscape into a lush oasis. But until now, no one knew for sure.

"This is the first, definitive study that provides unambiguous experimental evidence that soil moisture can control invasions of Argentine ants," says David Holway, an assistant professor of biology who conducted the study with Sean Menke, a graduate student at UCSD.

It also suggests that residents who stringently limit watering their gardens and yards may be able to reduce ant problems without using costly toxic pesticide treatments.

"Our study shows that if you irrigate, you may well have ant problems," says Holway. "And if it's dry, you're not going to get Argentine ants. If it's at all possible to limit your irrigation, you can decrease problems associated with Argentine ants."

The tiny dark-brown ants, which are about three millimeters in length, are thought to have entered the United States aboard ships carrying coffee from Brazil during the 1890s, then expanded throughout California and the southern parts of the United States.

In the Southeast, their proliferation may be now limited to some extent by the introduction of fire ants. But in California, where those competitors are largely absent, the ants thrive, killing and displacing native ants. In Southern California, Argentine ants are second only to termites as household pests.

The UCSD biologists conducted their experiments at five sites San Diego County: two reserves in the University of California Natural Reserve System (the Elliot Chaparral Reserve near the Miramar Naval Air Station and the Dawson-Mono Reserve near Carlsbad), the Los Peñasquitos Canyon Preserve, the Cabrillo National Monument and Tijuana Slough National Wildlife Refuge. At these ecologically different sites, the biologists manipulated soil moisture with drip irrigation for six months during the dry season, from May to October, and observed the effects on the ant populations.

After three months, the Argentine ants had 54 percent more nests in the irrigated sites. And when the water was shut off, the ants gradually retreated, reaching the levels of control sites after another three months.

Because irrigation increased plant growth around the study sites, the scientists also conducted experiments in which they suppressed plant growth with an herbicide. They discovered that the ant populations were 38 percent higher in the irrigated plots with plants than in those without plants, probably because of the presence of aphids, which provide an additional source of food for the ants.

However, the slight increase in the ant populations provided by plants was far less than that provided by water alone, leading the scientists to conclude that water, not plant cover, was the primary attractant for Argentine ants.

"These results are extremely clear," says Holway. "If you have wet soil outside of your home, if you irrigate your yard frequently, you're providing an environment that is attractive for Argentine ants."

The results also have implications for land-use managers who must deal with streams of irrigated water and other urban runoff from suburban developments year round.

"The extent to which urban runoff can be reduced or contained, problems associated with Argentine ants should diminish," says Holway, adding that he knows first hand how much of a nuisance Argentine ants are for residents in Southern California. "Whenever I'm out in the field and someone asks what I'm doing and I tell them I study Argentine ants, the first thing they want to know is, How do I get rid of the ants from my home?"

Related Links
University of California - San Diego

Birdsong Sounds Sweeter Because Throats Filter Out Messy Overtones
Bloomington IN (SPX) Apr 05, 2006
The purity of birdsong is owed in large part to rapid, controlled changes in the shape of the birds' upper vocal tracts, according to a new study of Northern Cardinals by scientists at Indiana University Bloomington, Purdue University and Australian National University. Their report will appear in next week's (April 4) Proceedings of the National Academy of Sciences.







  • US Struggling To Find New Disaster Chief
  • Pakistan To Relocate Town Destroyed By Earthquake
  • Engineers Making A Difference Worldwide
  • Tiny Water Purification Packet Helps Save Lives Worldwide

  • Severe Ethiopian Drought Claims Thousands Of Livestock Threatens Life
  • UN Decries Biodiversity Decline, Climate Change
  • Better Estimates For Future Extreme Precipitation In Europe
  • Climate Change Deal Will Fail Without US, China And India: Blair

  • Envisat Makes Direct Measurements Of Ocean Surface Velocities
  • NASA Scientist Claims Warmer Ocean Waters Reducing Ice Worldwide
  • Space Tool Aids Fight For Clean Drinking Water
  • FluWrap: Deadly Strain Divides

  • Common Clays Investigated For Use As High Tech Environmental Catalysts
  • New Bioproducts Research Centre Will Help Industry Create Forest Biorefinery
  • New Processing Steps Promise More Economical Ethanol Production
  • The Challenge Of Fueling The Chinese Replicator

  • Japan Developing First Fuel-Cell Powered Train
  • Plague Pits And Mass Burials
  • Supercomputer Explores Avian Flu Vaccine And Isolation Options
  • Rain Worsens Risk Of Disease In Drought-Stricken Ethiopia

  • Birdsong Sounds Sweeter Because Throats Filter Out Messy Overtones
  • Water Found To Be Main Culprit In Argentine Ant Invasions
  • Does Biodiversity Increase As Rainforest Area Expands During Global Warming
  • How Vitamin A And Meiosis Split Life In Two

  • China To Spend Over 1Bn Dollars Cleaning Up Songhua River
  • Evacuations Continue As China Gas Well Leaks After Blast
  • Subsurface Bacteria Release Phosphate To Neutralise Uranium Contamination
  • Universities Collaborate To Reduce Development Impact On James River

  • Why Are Letters The Shape That They Are
  • Technology Terror And Viagra Could Warp Sex And Relationships
  • Cortex Matures Faster In Youth With Highest IQ
  • New Light On Muscle Efficiency

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement