NC State Extension

Pest Problems After Storms – Fire Ants

Red Imported Fire Ant mound in a field

Fire ant mound in a field

Portions or entire areas of 74 of North Carolina’s 100 counties are considered generally infested with red imported fire ants. Fire ant mounds vary in size, usually in direct proportion to the size of the colony. For example, a mound that is 2 feet in diameter and 18 inches high may contain about 100,000 workers, several hundred winged adults, and one queen. Mounds are usually located in exposed areas as shown here. You may accidentally step on a nest or grab fire ants during cleanup activities in the yard.

During floods, fire ants form a raft to transport brood and the queen.

Fire ant “raft” floating on the water surface. (Photo – B. Drees, Texas A&M)

In areas of severe flooding, fire ants will abandon their nests and may form  “rafts” which drift in the water until they find ‘high ground’, such as a tree limb or some object. In these situations, the ants can pose problems during rescue and recovery efforts and other activities in flooded areas.

When disturbed, fire ants can deliver painful stings. Within 24 hours after a person is stung, a pustule-like sore usually forms at each sting site, which then usually itches intensively. Scratching the pustule may rupture the skin, leading to secondary infection and scarring. Just as with bee and wasp stings, a small proportion of people are highly allergic to fire ant stings and require medical attention after a stinging incident.

Fire ants are particularly fond of greasy-oily foods. While they typically an outdoor problem, disturbances during/after severe weather may bring them indoors in search of food or even “dry land” and thus into closer contact with people.

Here are some suggestions to follow if fire ants are common in your area:

  • Watch where you step when clearing debris in yards,
  • Insect repellents are not likely to be effective against fire ants.
  • When eating outside, keep all food and drinks covered while they are not being eaten. Dispose of food in garbage bags and trash cans. Keep trashcans covered and (preferably) away from the house.
  • Indoors, do not leave food exposed on tables, counter tops, or floors (in the case of dry pet foods).
  • If your need to treat a fire ant mound that is disrupting cleanup and other activities, drench the mound with a liquid insecticide. Products containing Sevin, cyfluthrin or bifenthrin and permethrin should work. Be careful applying pesticides near standing water or ponds and pools.  Fire ant baits work well, but they also take significantly longer time to effectively reduce the ant population and may not be as effective if there are other food sources (e.g, trash cans with old food) readily available.. A list of products that can be used against fire ants is available in the North Carolina Agricultural Chemicals Manual.

For additional information, consult Control of the Red Imported Fire Ant

Written By

Photo of Dr. Michael WaldvogelDr. Michael WaldvogelExtension Specialist (Household & Structural Entomology) (919) 515-8881 mike_waldvogel@ncsu.eduEntomology and Plant Pathology - NC State University
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