Do You Have Angry Fire Ants?

— Written By Glenn Detweiler and last updated by
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Fire ants aggressively attack anyone or anything that disturbs them or their mound. They did not exist in Catawba County until recently. The fire ants’ unique breeding habit of mating in the air makes it difficult for us to control their movement north. Also, since there are no natural predators of this ant here in North America, fire ants continue to move north in large numbers. The phorid fly controls them in South America, were fire ants originated. This fly is famous because it lays eggs in the ants’ body. The larva of this fly grow inside of the ant and eventually result in the decapitation of the ant’s head. Unfortunately, this fly cannot survive our cold winters.

Fire ants are reddish-brown at a glance and range in length from 1/8 to 1/4 inch. In addition to their physical characteristics and aggressive swarming behavior, they are identified by their painful sting, which produces a small white bump on the skin within 8 to 24 hours. Fire ants cause economic losses in yards, gardens, and agriculture. They construct unsightly mounds, which cause difficulty during mowing and can damage farm and lawn maintenance equipment. In addition, fire ants are attracted to electrical fields. Short circuits and damage to electrical equipment can be the result of fire ants.

Fire ant impact upon our lives can be minimized by knowing their eating and living habits. With patience, we can apply mechanical, biological, and chemical pressure when these insects are most vulnerable. Scientist call this synchronized effort, Integrated Pest Management (IPM) practices. The most effective chemical control methods for imported fire ants result in killing the queen or prohibiting her from producing more worker ants. However, the queen is called a queen because she does not work or collect her own food. So she is never outside her mound for us to attack her with a spray. No holes are on undisturbed mounds. All access is through tunnels surfacing around 2 to 3 feet away from the visible part of the mound. The queen is relocated in the ant mound based on the temperature of different levels. If danger is sensed by the workers she is moved to the bottom of the mound or moved into one of the tunnels that go horizontally away from the mound. Scientists have worked to figure out how to get poison to her to either kill her or at least prevent her from reproducing. In order to trick the worker ants into carrying poison to the queen, scientist mix grits and vegetable oils with poison. The worker ants carry it into the colony’s mound where it is processed by other workers to be fed to the queen. When ants bite our children, grandchildren, and pets, we want a poison that kills the ants immediately. Mound drench type products are satisfying because we see dead ants quickly after application. But knowing worker ants carry food into the mound for the queen, we need to keep the workers alive long enough for the poison to reach the queen.

Researchers have developed a “two­step” broadcast method for fire ant control. This method normally carries a poison which causes the queen’s eggs to not hatch and another slow-acting poison to eliminate the worker ants a few weeks after spraying. Spreading this over the designated area eliminates 90% of the ants. Step two requires individually treating any ants which escaped the first step. This method can effectively control heavy fire ant infestations when conducted twice yearly. This method is also the most economical. When mounds are in smaller numbers it is cheaper to treat the individual mounds.

Five general “do’s and don’ts” for killing fire ants include:
1) Apply bait when foraging ants are actively searching for food. Place a potato chip 3 feet from an active mound. If ants are seen on it within 30 minutes, it’s a good time to apply bait.
2) Do not disturb mounds before bait application.
3) Apply bait when the ground and grass are dry and rain is not expected for the next 12 to 24 hours.
4) Use fresh bait, preferably from an unopened container or one that has been tightly sealed and not stored long. Worker ants will not pickup rancid bait.
5) Ants are less active during cold and hot periods, when soil temperature is less than 70°F or greater than 95°F.

Although many fire ant baits are available, we can better pick out the insecticide that fits our specific situation by understanding that some baits make the queen lay infertile eggs (insect growth regulator) and some poisons take weeks to kill worker ants (allowing workers to carry poison into the mound). READ AND FOLLOW LABEL INSTRUCTIONS. Make certain the area you plan to treat with the bait product is listed on the label. It must be applied only in those areas. Yards have many pesticide options, however only a few baits are labeled for use in vegetable gardens and agricultural areas such as cropland, pastures, and orchards. The cost of these chemicals vary greatly.

The Catawba County Cooperative Extension Service can answer your questions about fire ant control. Call our office at 828-465-8240. You can also find information on the Catawba County Center website.