Dale K. Pollet, Beckley, Patricia A., Merrill, Thomas A.
Fire ants can be a serious problem after hurricanes – particularly in flooded areas, according to experts with the LSU AgCenter.
"When the waters rise, the fire ants are forced out of their underground nests and float in a mass on top of floodwaters," said LSU AgCenter entomology associate Patricia Beckley. “For example, we saw that recently when people were unable to wade through the waters surrounding the New Orleans Superdome (after Hurricane Katrina) without encountering masses of floating fire ants.”
"In all areas of Louisiana infested with the red imported fire ant, these ants and their colonies can present a potentially serious medical threat to people and animals during and after times of flooding," said LSU AgCenter entomologist Dr. Dale Pollet, adding, "Floodwaters will not drown fire ants. Instead, their colonies will actually emerge from the soil, form a loose ball, float and flow with the water until they reach a dry area or object that they can crawl up on."
Floating fire ant colonies can look like ribbons, a mat or an actual "ball" of ants floating on the water, according to the experts, who say these writhing masses of ants contain the entire colony – worker ants, eggs, larvae, pupae, winged males and females and queen ants.
As the floodwaters recede, these floating fire ant colonies will cling to any structure that they come in contact with and are attracted to anything that might give them shelter until a mound can be re-established in the soil, Pollet and Beckley explain.
"This means debris piles from the floodwaters or piles of items from flooded homes are potential nesting sites for fire ants," Beckley said. "So you need to be cautious and be aware that fire ants can be under anything."
The LSU AgCenter experts also offer these tips on avoiding fire ant bites when cleaning up after flooding:
Recommendations on treating for fire ants after a storm differ from the usual ones that call for the use of baits that are carried back to the colony and eventually kill it.
"At the time of flooding or right after flooding, general preventive treatments for controlling the fire ants are out of the question," Pollet said. "Ant colonies or ants encountered now need to be dealt with quickly."
The experts say aerosol spray products containing pyrethrins or pyrethrum derivatives (tetramethrin or allethrin) or Bengal’s Deltramethrin dust labeled for use on "ants" or "crawling insects" can yield a quick knockdown of the insects and will break down quickly.
"Spray or dust as many of the ants as possible," Pollet advised, cautioning, however, to avoid waterways, since pyrethroids can be quite toxic to fish and crustaceans. "Just spray or dust surfaces, cracks of infested objects and debris. Then return after the treatment has had time to work."
Although much of the flooding the state has seen this year has receded, the LSU AgCenter experts point out that ants are particularly dangerous during flooding.
They say to avoid floating mats of fire ants during a flood and to be careful not to let ants come into contact with oars if you are in a boat, since that would allow ants to cling to the oars and move into your boat. They also say to wear protective clothing, such as rubber boots, rain gear and cuffed gloves, that can help prevent ants from reaching your skin when working in floodwater.
“While ants are ‘rafting’ (floating in water), they can inject up to two times the venom of a normal sting,” Beckley cautions. “Remember, if ants contact the skin they will sting.
"You should try to remove any ants that get on you by immediately rubbing them off. But ants can cling to the skin if submerged and even a high-pressure water spray may not dislodge them."