May 12, 2015
Here’s a great article by one of the guys at the state of Alabama’s extension office on fire ants. We agree with him, we have yet to hear from someone who likes fire ants. We would be glad to have them no longer be a part of our lawns and gardens.
Fire Ant Control
Fire ants. Enough said. Right? I hate them, you hate them... EVERYONE hates them. In some circles, you’ll likely find folks that hate snakes, some that love snakes. Some people love other varmints (rats and mice), while others find them abhorrent. I have yet to find anyone that actually likes fire ants. While there are certainly those individuals that find the biology and sociobiology of fire ants fascinating, no one finds delight in stepping in a giant mound of ants on a gorgeous summer day.
While my contemporaries and I can’t remember a time in our life that fire ants weren’t around, go back a generation or two and you will find people that can remember the “good ole days”; those days when fire ants were absent or at least much less common than they are today. Fire ants are actually a rather new pest in Alabama lawns. When we talk about fire ants, there are actually three species of ants that we must discuss: the black imported fire ant (Solenopsis richteri), the red imported fire ant (Solenopsis invicta), and a fertile hybrid of the two species; all natives of South America. The black imported species arrived in the United States around 1920 and the red imported fire ant arrived during the early 1940’s, both via the port of Mobile, AL. As the populations of both species increased, they migrated or were moved north via plants, sod, soil and other means of transportation. As of fall 2014, all 67 counties of Alabama were infested by one or both species of the insect. Aside from the bites and stings that fire ants deliver, there are several other problems that can arise from ant hills, including destruction of machinery (hay and lawn mowers) and injury to farm animals.
It is quite common for my colleagues and I to get calls about controlling fire ants. Farmers, gardeners, and commercial property owners all are interested in “getting rid” of fire ants around the home. Ants are said to be the most abundant insect on the face of the planet with more than 10,000 different species identified. One ant “super colony” found in Japan was estimated to contain over 300 million ants with 1 million queen ants spread throughout 45,000 individual nests connect by tunnels over an area of 670 acres! With that said, consider how difficult it is to “get rid” of ants by treating mounds individually like most homeowners attempt to do. Anthills are much like icebergs in that there’s much more below ground than what you can see. Have you ever treated a mound and killed it, only to find a new mound right beside that one the next day?
Eradicating ants is simply not a viable option. However, managing fire ants in your lawn and other areas to a level of tolerance is something that can be achieved by the average homeowner. As mentioned before, treating mounds is not nearly as effective as it is satisfying to the person doing the applications. The most effective management strategy is to use baits in the lawn. Baits utilize the natural biology of ants to forage for food in wide areas around the mound. By using the ants’ biology, we can greatly reduce the amount of insecticide that is applied, using very low densities of poison bound to particles that the ants find delectable. Once collected, the foraging ants will transport the insecticide back to the nest and feed it to the queen or the larvae in the brood chambers. While different insecticides have different modes of action, baits are typically growth regulators that affect the development of eggs and larvae in the nest. While baits generally take longer to kill the mounds, often 4 to 6 weeks, the results last much longer than typical ant poisons. In fact, 80% to 90% control has been achieved when applying bait treatments once in the spring and once in the fall.
Another potentially promising control is by an ant decapitating insect called phorid flies; a small humpbacked fly that resembles a small fruit fly. This small fly is capable of doing great harm to fire ants by utilizing the ants’ bodies as pupal chambers for their larvae. The fly will deposit eggs in the thorax of the fire ant, temporarily paralyzing the ant. The injected egg develops in the ant’s thorax until after about ten days, the ant dies after the larva moves into the ant’s head. The head falls off and the larva eventually pupates in the safety of the hard chitin shell that once housed the ant’s jaw muscles and brain. Adult flies emerge from pupae about 45 days after the original attack. Phorid flies may not be better than pesticides in many local, short-term circumstances, so there will always be a role for some careful use of pesticides. However, over an entire region and over decades, biological control agents like phorid flies are likely to be a more economic and safe way to reduce the pest status of imported fire ants.