Team uses parasitic flies to control fire ants on base

  • Published
  • By Capt. Joe Knable
  • 19th Airlift Wing Public Affairs
LITTLE ROCK AIR FORCE BASE, Ark. --  A team from the University of Arkansas Cooperative Extension Service is conducting a study of red imported fire ants on base.

Dr. Kelly Loftin and Dr. John Hopkins, natural scientists with the extension service, were recently invited by Jim Popham, the base natural resources manager, to conduct these ant studies as a non-chemical means to control the non-native ant population.

They were joined June 7 by Allan Beuerman, a Pulaski county extension service agent, Ricky Corder of the extension service and Mr. Popham to collect a golf ball-sized cluster of the fire ants from each of eight different ant hills around base. The scientists previously surveyed the base for suitable locations for collection.

The ants were accidently imported from South America and introduced with soil used with ballasts in cargo shipments to Mobile, Ala. from approximately 1920 to 1930, said Dr. Loftin. The ants have been found throughout the southeast U.S., California, and recently as far away as Australia and Taiwan. The natural enemies or diseases that control the imported fire ants in their natural habitat do not exist here.

"With an invasive species," said Mr. Popham, "there are no natural controls, so they just overwhelm the ecology and the population explodes" to eight times what they are in their native South America.

Fire ants are one of the few ants that can sting people like a bee, but these ants sting multiple times, said Mr. Beuerman. It's very itchy afterward.

Fire ant hills are a mound of loose dirt whereas native ant hills look more like a chimney top. When disturbed, the red ants will swarm to the top, unlike native ants, said Mr. Beuerman.

The collection took about three hours. The scientists placed small sections of PVC pipe over anthills. The ant hills were disturbed by whacking the hills with shovels to collect the ants. They then tapped the ants crawling on the PVC pipe into a bucket. The bucket and the top of the PVC pipe collection device are lined with fluon, a Teflon-type substance that contains the ants and keeps them from crawling on and biting the scientists.

These particular fire ants, "Solenopsis invicta," were then shipped to a lab in Gainesville, Fla., where they will be parasitized by a group of Phorid flies, "Pseudacteon curvatus," said Dr. Loftin. These flies are about the size of a pinhead. It's important to introduce multiple species of Phorid flies over time to effectively control the ant population. They have introduced three species so far in Arkansas and they hope to introduce a fourth soon.

The fly lays eggs in the ant, said Dr. Loftin. The egg hatches into a larvae (a maggot), which makes its way to the head and starts consuming the contents of the head, where it transitions to the pupal stage. Digestive enzymes then cause the head to fall off.

"When the Phorid flies are present, the ants' behavior is disrupted. The ants gather less food, which leads to smaller ant colonies, and the native ant species can then compete. Over time and with multiple Phorid fly species, this process gets the imported fire ants much closer to their native density which is about eight-fold less than their current density in the United States," said Dr. Loftin.

The team will collect another batch June 14 and will release each batch of parasitized fire ants approximately one week after the collection, after receiving them back from the USDA, said Dr. Loftin.

The base has other invasive species, such as plants like honeysuckle and wisteria. "These are landscaping plants that 'escaped captivity' into the natural area," Mr. Popham said. Contractors spray these invasive plants to control them.