Argentine Ants Vol. 2, No. 24

Linepithema humile

Order: Hymenoptera
Family: Formicidae

“These ants are everywhere! They’re crawling up and down all of the trees, and they have trails all around the outside of the house. Sometimes they get in the kitchen or other parts of the house, but mostly they are outside. They’re so bad that they have even run the fire ants off!”

Argentine ants are non-native ants that first entered the US at New Orleans in the late 19th century, which means they have been here longer than fire ants. Since then, they have spread into many areas of Mississippi, but because they do not tolerate cold winter weather well, their distribution continues to be spotty, especially in the more northern portions of the state. Heavy infestations are much more common south of I-20, but isolated infestations occur as far north as Starkville, and even further north following a series of mild winters.

Although they have no sting, Argentine ants are so aggressive and become so numerous that they really do displace fire ants, as well as other ant species, especially in shady landscapes that have lots of trees and shrubs. Argentine ants do not build large visible mounds like fire ants. Instead, they will have hundreds of small, inconspicuous nests in protected areas such as: under flower pots, under piles of leaves or mulch, under bark of dead trees, in dead logs or hollow trees, in the soil, under debris lying on the ground, and similar sites. Each of these individual nest sites will have one or more queens, and they communicate with and live in harmony with other nearby nests. It’s more like there is one big mega-colony in a landscape, rather than a bunch of small independent nests.

Control: For landscapes with heavy populations of Argentine ants, successful control is best defined as just being able to keep the ants from getting indoors—most of the time. In most cases, it is not really practical to attempt to completely eliminate Argentine ants from the landscape. But there are methods and tools that can be used around the outside perimeters of buildings to help keep indoor invasions to a minimum. These include cultural practices such as pruning limbs and shrubs that touch the building and keeping debris, mulch, and leaf litter to a minimum around the immediate exterior of the building, as well as exterior perimeter insecticide treatments. Argentine ants do not take fire ant bait well and even the baits that they do take do not provide very good control.

See Extension Publication 2407, Control of Argentine Ants and Odorous House Ants in the Home, for more detailed information on Argentine ant control: http://extension.msstate.edu/sites/default/files/publications/publications/p2407_0.pdf .

Also see pages 10 - 14 of Extension Publication 2443, Control Household Insect Pests, for more information on control of home-invading ants: http://extension.msstate.edu/sites/default/files/publications/publications/p2443.pdf .

Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service. The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.

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