GAINESVILLE, Fla. — University of Florida Institute of Food and Agricultural Sciences researchers have discovered a new invasive ant species in south Florida that can have dire consequences for homeowners and for surrounding ecosystems.

The yellow ant, Plagiolepis alluaudi, is native to Madagascar and is already invasive in several Caribbean Islands, including Barbados, St. Lucia and Nevis, among others, said Thomas Chouvenc, UF/IFAS assistant professor of urban entomology. The ant has also previously been detected in Australia and Hawaii, he said.

In early 2017, researchers spotted the yellow ant in the continental United States for the first time. The new ant species was found in the Riverland neighborhood of Fort Lauderdale, said Chouvenc, who is based at the UF/IFAS Fort Lauderdale Research and Education Center.

“Over a period of six months, the big-headed ants that were dominant in that area were apparently displaced by this tiny yellow ant, which was quite surprising,” Chouvenc said. “Subsequent surveys in the Riverland area lead us to believe that the new ant species could have been established for several years before being detected.”

The good news is that the yellow ant does not bite or sting, Chouvenc said. The bad news is that because the ants are so small, they are hard to detect before they reach high population density, and become a nuisance, he said. “They also have an intricate nesting system with multiple queens, which results in super colonies,” Chouvenc said. “They are small and hard to see at first, and by the time you detect them, the colonies are so big and spread out that they are hard to control,” he said.

Nests were detected in dead branches of vegetation, both on living trees and on twigs on the soil surface, Chouvenc said. Forager ants were eventually found infesting a home, and researchers used baits as an attempt to stop the infestation.

“Within a couple of days, the home infestation stopped. However, it had limited success because large ant populations are established outside of the home, and we only killed a small fraction of the foraging population,” Chouvenc said. “Within a week, subsequent infestations were observed. As long, as the established population outside the home is not affected, more foragers will be coming into the home,” he said.

Homeowners can manage an infestation by regularly baiting populations with sweet liquid baits, but in areas with high ant densities, recurrent infestations may be unavoidable, Chouvenc said. “Unfortunately, this will probably be another ant on the invasive species list that will cause homeowners problems down the road,” he said.

The recent hurricane may have contributed to the problem, Chouvenc said. “With Hurricane Irma, a lot of plant debris were scattered during and after the storm, and it may have helped disperse this new ant species,” he said. “However, as a tropical species, we hope the little yellow ant will be contained to south Florida. But looking at patterns of invasive ants in the southeast U.S. over the past 50 years, it may be a small ant, but it still going to be a big problem.”

In addition to being a household pest, this ant can potentially impact Florida agriculture, Chouvenc said. UF/IFAS researchers reported that the new invasive ant is strongly associated with aphids, mealybugs and scale insects, which can harm crops and ornamental plants.

“Unfortunately, we know very little about this new ant species. We only started investigating it, so it will take time to figure out what impact this new ant will actually have on Florida communities,” he said.

An article on the new ant species will be published in an upcoming issue of Florida Entomologist.

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The mission of the University of Florida Institute of Food and Agricultural Sciences is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS works to bring science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents. Visit the UF/IFAS web site at ifas.ufl.edu and follow us on social media at @UF_IFAS.

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