Clemson scientists hot on trail of ‘crazy’ ant species that might soon invade S.C.
CLEMSON — A dangerously prolific invasive ant species, which first surfaced in the United States almost 15 years ago, has been spreading throughout the South ever since and now appears to be on the verge of entering South Carolina for the first time. But a team of Clemson University scientists is hot on the trail.
Native to South America and the Caribbean, the tawny crazy ant was originally found in Texas in 2002. But it has since entered other Southern states, such as Florida, and in 2013 it was discovered in several counties in Georgia. Two years later, it was found as far north as the Savannah River, which indicates it soon might invade South Carolina.
“The predictive models show that the tawny crazy ant could become established in South Carolina in 2016, especially along the coastal counties from Jasper up to Georgetown,” said Eric Benson, professor and Extension entomologist in the plant and environmental sciences department at Clemson University.
“Once established, this invasive species multiplies very quickly and can overwhelm its new surroundings,” he said. “These ants feed aggressively on anything organic and can outstrip an area of available food resources. They can even kill ground-nesting animals and become a danger to poultry, livestock and agriculture. They’re called crazy ants because they run around like they’re crazy, like they don’t know what they’re doing. But they do know what they’re doing, and they are highly efficient foragers.”
Unlike fire ants, tawny crazy ants don’t sting or bite humans. Rather, it’s their sheer numbers that create the most problems. Because their colonies have multiple queens, they can reproduce far faster than most of their ant counterparts. In fact, tawny crazy ants can take over entire areas, both on the ground and in trees and foliage. In the process, they can kill all other ants in their path. This includes “bad” ants such as fire ants, but also “good” ants, which comprise about 90 percent of the ant population.
South Carolina is home to an estimated 200 species of ants, and most of them are beneficial to the environment. But when an invasive species takes over, it can displace all the other ant species, negatively changing the ecology.
“Through sheer strength of numbers, tawny crazy ants can rise to become the predominant species,” Benson said. “In terms of destroying fire ants, this might seem like a panacea. But in reality it’s not the best solution. This is because a monoculture of one particular ant is not as good for the health of the environment as is a diverse group of ants. To some people, tawny crazy ants might seem like they’re only a nuisance because they don’t sting. But in urban settings, they can short out electrical equipment and infest homes. If you have millions of ants moving into a nursing home, a school, a hospital or any place that’s a sensitive environment, they will go from being a nuisance to an extremely serious problem. Entire floors of buildings can become covered with these ants.”
Several Clemson scientists, including Benson, are completing plans for a project to survey areas along South Carolina’s southern coast to see if the ants are there and, if so, to document their spread and habits. The team includes Pat Zungoli, professor of entomology and interim chair of the plant and environmental sciences and agricultural sciences departments; Billy Bridges, a statistical analysis expert in the mathematical sciences department; David Bowers, a graduate student in entomology; Jinbo Song, a post-doctoral scholar in plant and environmental sciences; and Brittany Ellis, a lab technician. Another important player is former Clemson Extension agent Tim Davis, who is now with the University of Georgia.
“We’ll be surveying in places where we think these tawny crazy ants might show up first, and if they show up, we’ll document what happens,” Benson said. “But ultimately we’ll want to look at control strategies. If left to their own devices, a relatively small number of these ants can grow into hundreds of millions. So they are far easier to control if they are dealt with early on.
“In South Carolina, at least, we’ll have the winter as part of our arsenal, as opposed to portions of Texas and Florida that are pretty much always warm, so there should be things that we can do — taking into account our four seasons — that would help with an integrated pest-management strategy.”
On their own, tawny crazy ants establish new territory slowly because they don’t have winged forms that can fly to distant places like some ants do. But since they thrive in a variety of conditions, from shady wooded areas to dry, sandy fields, they tend to inhabit places where they can crawl aboard cars, trucks, boats, shipping containers and plant materials and move from one place to the next like tiny stowaways.
“They’ll often nest in areas that are disturbed or places that normally you might park a vehicle or you might camp,” Benson said. “They’re also found in ports of entry where there’s a lot of activity and a lot of containers and once they’ve moved from point A to point B, they crawl off and begin the process of taking over the new location.”
Treatments against the spread of tawny crazy ants are relatively limited. Insecticides will kill the ants, but this doesn’t help much if you kill a million of them and still have 99 million left. The effectiveness of baits is also limited because the ants strip them to nothing without suffering enough casualties to slow them down. This is why early detection and treatment are so important. Benson and his team are already in contact with dozens of regulatory officials and pest-control operators throughout the state to be on the lookout.
“With other species of pest ants in South Carolina, their numbers aren’t as high in March when they’re just coming out of wintertime. They’ve coalesced their nests and basically put all their eggs in one basket. So we can kill a lot of ants with very targeted insecticides or baits,” Benson said. “This might be something we’ll be able to use against the tawny crazy ant. Unlike more southern areas, we’ll have the benefit of using the winter as part of our control strategies. With pest ant control, the sooner you do something, the better off you are. Research has shown that if you suppress them early in the year, their numbers in July through October, when they’re usually at their peak, will be much lower and easier to combat.”
The Clemson project will begin soon. Its goals are to survey for the presence of tawny crazy ants in the state, establish an ant diversity baseline for species in areas where tawny crazy ants are likely to colonize, and monitor the impact and interactions of ant species before and after the invasion. The ultimate goal of the research is to provide information that will help South Carolina residents and managers of wildlife areas understand the impact of tawny crazy ants and to develop strategies to aid pest-management professionals in controlling these ants.
The scientists will employ techniques that are similar to ones already being used in Georgia. Once they’ve chosen an area to investigate, they will string long lines – usually about the length of a football field – and then sample for ants about every 30 feet. This will establish a baseline for what’s there now. If the tawny crazy ants do appear, a second sampling will show what kind of impact the invasive species has on the other ants.
“We’ll use a host of methods because these ants can be down in the leaf litter, they can be in a log, they can be on a tree,” Benson said. “We’ll use pitfall traps that the ants fall into and can’t escape. We’ll take small logs and break them up in different areas of the forest to see what ants are there. And we’ll put out baits, which are usually either bits of hotdogs or sweet cookies, and collect the ants that swarm on the baits. So if the invasion does occur as expected, we’ll have already acquired some knowledge that will help us fight back.”