Joanna Radford
Home, Farm, & Garden
Fire ants have been a hot topic over the last few months. The North Carolina Department of Agriculture and Consumer Services has been scouting Surry and surrounding counties for signs of this pest. I thought I would share some information about these pesky invasive insects.
Fire ants, or more specifically red imported fire ants (Solenopsis invicta), are native to South America. These ants were first found in North Carolina in 1957. Their foothold began in Brunswick County near Wilmington. They have since spread to seventy-seven of the one hundred counties in North Carolina.
How does one identify fire ants?
- Adult red imported fire ants are reddish to dark brown and occur in five forms:
- Minor workers, about one-eighth inch long
- Major workers, about one-quarter inch long
- Winged males
- Winged females, each about one-third inch long
- Queens, about one-third inch long
- The telltale sign is the two nodes present between the thorax and abdomen.
Fire ant mounds vary in size but are usually in direct proportion to the size of the colony. For example, a mound that is two feet in diameter and eighteen inches high may contain about one hundred thousand workers, several hundred winged adults, and one queen (or sometimes multiple queens).
If you break open an active fire ant mound, you typically find the “brood”—whitish, rice grain-like larvae and pupae. These immature ants will eventually develop into workers or winged adults. Mounds are typically constructed in open sunny areas. Those mounds constructed in clay soils are usually symmetrical and dome-shaped, while mounds built in sandy soils are often irregularly shaped.
The red imported fire ant can be difficult to distinguish from native ant species. However, these are the only ants that will cause a small blister to form on your skin once bitten. Foraging fire ants do not enter the colony through the mound but enter via tunnels that extend beyond the mound.
How do fire ant colonies spread?
Imported fire ants spread naturally during their mating flights. This spread is usually one mile or less, but flights of up to twelve miles have been recorded. The flights occur most commonly in the spring or early summer, one or two days after a rain, when the weather is warm and sunny and the wind is light.
Fire ants are also great hitchhikers. They can catch a ride on sod, nursery stock, earth-moving equipment, hay, pine straw, and potted plants.
The North Carolina Department of Agriculture and Consumer Services regulates the shipment of nursery and sod farm items, as well as baled hay and straw, to areas outside of the quarantine zone. More than three-quarters of North Carolina is under quarantine for imported fire ants. Surry County is not in the quarantine area currently. More information on the NC IFA quarantine can be found at www.ncagr.gov/divisions/plant-industry. NC IFA Quarantine Information
Why do fire ants appear to sting all at the same time?
Fire ants are sensitive to vibration or movement and tend to sting when the object they are on moves. For example, when fire ants swarm up a person’s leg, and the person jerks or moves, that movement can trigger multiple ants to sting at once. Although fire ants emit communication chemicals called pheromones to elicit specific behaviors such as alarm reactions, trail formation, and queen recognition, there is no known pheromone that stimulates ants to bite and sting simultaneously. It is simply a coordinated response to external movement.
What should I do if I get stung by fire ants?
There is not much you can do except watch the affected area for excessive swelling, itching, or redness, or other symptoms such as shortness of breath, thickening of the tongue, or sweating that could indicate a severe allergic reaction. If this occurs, seek medical attention. Otherwise, treat stings as you would stings of other insects and keep them clean and intact to avoid secondary infections.
How are fire ants controlled in the landscape?
There are two approaches to chemical control of fire ants: a mound treatment and a bait treatment. The goal of either treatment is to control the queen.
Individual mound treatments are often more environmentally and ecologically acceptable because they use less insecticide and limit the amount of area treated as compared to broadcast treatments. Mound treatments are also quicker than bait treatments.
Bait treatments are effective when foraging workers bring the poison bait back to the colony. However, the treatment is slower because the poison must work its way through the colony before it will be consumed by the queen. The queen does not consume sustenance directly. It must be passed among the colony before she consumes food.
There are some good strategies for managing fire ants that include using both mound treatment and baits. This is referred to as the two-step method.
Hopefully, it will be some time before Surry County has fire ant activity. However, homeowners should be aware of possible movement into the county and be on the lookout. Report any fire ants that are found.
