Management

It is important to understand that it is not currently possible to completely eliminate European fire ants from areas that they have invaded.  If you already have an infestation of European fire ants on your property, there are some management strategies that may reduce the number of ants or the density of nests. This section has three parts: Prevention, Management with insecticides and Management without insecticides. You can also download a PDF of this here.

BEWARE

Most new infestations are caused by people unknowingly introducing these ants to new areas via potted plants, soil, compost or other organic materials. If you have an infestation, DO NOT move plant/soil material to other areas.

Prevention:

Be aware that infestations currently occur in many coastal communities and some inland sites.  If you do not already have the ants on your property, you can help prevent future infestations by carefully inspecting all plant and nursery materials (potted plants, tree balls, soil, compost, wood chips and logs) prior to installing them in your yard.  If you find ants infesting potted plants, you can drive the ants out by submerging the pots in water for at least one hour.

Management with insecticides:

If you choose to use pesticides, always follow the label directions.  You can do a search for insecticides that are registered for use against ants in Maine at the Maine Board of Pesticides Control website. Currently, the most effective way to suppress ant populations is to use bait-formulated insecticides.  Baits consist of an insecticide blended with a sugar, oil or protein food.  They are more effective than contact insecticides because they are carried back to the nest and fed to queens and brood.  They also target ants more specifically than contact insecticides or sprays, and thus have less impact on beneficial insects and other wildlife. Some baits can be applied either as broadcast treatments or in commercially available re-usable bait stations, which makes the bait less accessable to wildlife.

The European fire ant is generally not well controlled by most commercially available insecticides.  Our experiments demonstrated that two applications of Amdro® (Hydramethylnon) or one application of Extinguish® (methoprene) followed by one application of Amdro® result in the greatest reduction of ant activity.  Some people have reported good control using liquid sugar bait containing a low concentration of boric acid (less than 1%).  Although we have had positive results with this in laboratory trials, our field results have not been as successful.  If you choose to utilize boric acid, it is essential that the concentration is 1% or less.  Higher concentrations repel the ants or will kill workers before they can feed the rest of the colony.  We are continuing to evaluate new bait formulations, active ingredients and methods of delivery.

Since the efficacy of baits is dependent upon feeding, these materials should be used during early to mid summer, the period during which the queens and ant brood are consuming the most food.

Remember that no strategy can completely eliminate the ants.  There is some evidence that repeat applications may just cause the ants to move into adjacent areas.

Most ant baits are not approved for use directly within vegetable garden beds. However, they can be used within ornamental gardens and butterfly gardens containing plants not intended for consumption by humans or livestock.  For vegetable gardens, baits can be applied outside the perimeter. For schoolyard gardens, the perimeter is the outside edge of the landscape timbers or railroad ties used to make the raised garden beds.

Management without insecticides:

European fire ants generally nest under stones, boards, leaves, logs and other debris.  If you remove these nest sites from your yard or garden, you may reduce the density of nests and thus the number of ants.

These ants also require moist habitats.  Reducing irrigation or increasing solar exposure (by mowing tall grass or pruning overhanging shrubbery) may make parts of your property less hospitable to the ants, causing them to move elsewhere.

Pouring boiling water directly on nests may be effective at destroying individual surface nests.  However, European fire ant nests are often cryptic and located in protected locations, so this technique is not generally effective.