If ants invaded your house this summer, you’re not alone. Millions of the little insects move inside during Georgia’s hot, dry summer.
They’re just looking for a little water and a little food, said Jacob Holloway, a University of Georgia graduate studying Argentine ants.
That exotic invasive species has taken over much of the southern United States since they arrived with a shipment of Brazilian coffee in the late 19th century.
But rain sometimes drives them indoors, too, said Holloway.
When it’s really wet, they’re also prone to move inside from their shallow, drenched nests.
“They want to get away from flooding,” he said. “But what’s really driving them to get inside your home is water — primarily water — and a hospitable environment and food.”
Fortunately, Holloway said, those plagued by ants have some weapons to use against them.
Sealing up food in the pantry helps. Although worker ants are tiny, about a tenth of an inch long on average, they have a hard time with air-tight containers.
“But in general, you’re going to have to use some kind of chemical,” said Holloway, who has conducted research to see if natural repellents such as rosemary, spearmint leaves or soybean oils worked to keep Argentine ants out. “Everything I tested didn’t work, unfortunately,” he said.
But chemical gels and ant baits, particularly the Combat line, do work, said Holloway and UGA entomologist Dan Suiter. Controlling Argentine ants outside the house is tougher, since ant colonies are expansive.
But homeowners can make the environment less hospitable, Suiter said. The first thing is to minimize the use of mulch outside. Argentine ants usually lurk pretty close to the surface, in relatively damp, cool areas like the bottom of a thick layer of mulch.
“Use just enough to retain some moisture in the soil,” he said. “But you don’t need 10 inches. People tend to over-mulch.” Still, often the only way to do anything about ants outside is to call a professional pest control company, Holloway said.
The ants have proliferated this year, probably because they got a head start on summer during a mild winter. One year ago, the ants weren’t so numerous due to an unusually cold winter in 2011 that knocked down their numbers, Suiter said.
At the same time people are seeing lots of non-stinging Argentine ants, another kind of invasive ants has been nearly invisible this summer — the stinging fire ant. But it’s only those signature fire ant mounds that are absent, not the ants themselves.
“They only build those mounds up after a lot of rain,” said UGA entomologist and fire ant researcher Kenneth Ross. The fire ants themselves are just keeping cool deep underground.
“I don’t know of any evidence that their populations have declined here,” Ross said.
Scientists trying to knock back fire ant populations hope eventually to see some evidence that fire ant numbers really are declining. Along with scientists in states surrounding Georgia, UGA entomologist Wayne Gardner has been raising and releasing a couple of species of tiny parasitic flies over the past few years. The flies lay their eggs in fire ant workers. When the flies’ larvae begin growing and eating inside the wasp, they move to the ants’ heads, which fall off, allowing the baby flies to emerge to start a new generation.
Since the release program began, the decapitating flies have shown up in every Georgia county, Gardner said. The flies only prey on fire ants, he said.
Gardner hopes the flies are helping control fire ants, but it’s really been too dry to say for sure, he said.
“It’s hard to assess that, particularly with the drought and heat conditions we’ve had,” he said. “We’re seeing a decrease in mounds. I’d like to take some credit, but I really think high temperatures are eliminating some colonies and driving others underground.”