Ant management requires diligent efforts and the combined use of mechanical, cultural, sanitation, and often chemical control methods. It is unrealistic and impractical to attempt to totally eliminate ants from an outdoor area. Focus your management efforts on excluding ants from buildings or valuable plants and eliminating their food and water sources. Reducing outdoor sources of ants near buildings will reduce the likelihood of ants coming indoors.
Regularly inspecting your home for ants or ant entry points is an important part of an IPM program. Monitor for ants near attractive food sources or moist areas. Ants may invade kitchens, bathrooms, offices, or bedrooms. Inspect under sinks, in cupboards, and along pipes and electrical wires. Look for large trails of ants or for just a few stragglers. Straggling ants are scouts randomly searching for food or nesting sites. When you spot ant trails, try to follow the ants to where they are entering the building and to the nest if possible. Look indoors and outdoors for holes or cracks in foundations or walls that provide entry points to buildings.
To keep ants out of buildings, caulk cracks and crevices around foundations and other sites that provide entry from outside. Ants prefer to make trails along structural elements, such as wires and pipes, and frequently use them to enter and travel within a structure to their destination, so look for entry points in these locations. Prior to caulking, some pest management professionals may apply products containing silica aerogel (sometimes combined with pyrethrins in professional products such as EverGreen Pyrethrum Dust) into wall voids before sealing them up.
Indoors, eliminate cracks and crevices wherever possible, especially in kitchens and other food-preparation and storage areas. Store attractive food items such as sugar, syrup, honey, and pet food in closed containers that have been washed to remove residues from outer surfaces. Rinse out empty soft drink containers or remove them from the building. Thoroughly clean up grease and spills. Remove garbage from buildings daily and change liners frequently.
Look for indoor nesting sites, such as potted plants. If ants are found in potted plants, remove the containers from the building, then place the pots for 20 or more minutes in a solution of insecticidal soap and water at a rate of 1 to 2 tablespoons of insecticidal soap per quart of water. Submerge so the surface of the soil is just covered by the water-soap solution.
Outdoor ant nests may be associated with plants that support large populations of honeydew-producing insects such as aphids, soft scales, mealybugs, or whiteflies. Avoid planting such trees and shrubs next to buildings, or manage honeydew-producing insects. Keep plants, grass, and mulch several inches away from the foundation of buildings, because these items provide nesting sites for ants. Fix leaky faucets and sprinkler heads; these attract thirsty ants.
When numerous ants are found on plants, they are probably attracted to the sweet honeydew deposited on the plants by honeydew-producing insects such as aphids or soft scales. Ants may also be attracted up into trees or shrubs by floral nectar or ripening or rotten sweet fruit. These ants can be kept out by banding tree trunks with sticky substances such as Tanglefoot. Trim branches to keep them from touching structures or plants so that ants are forced to try to climb up the trunk to reach the foliage.
When using Tanglefoot on young or sensitive trees, protect them from possible injury by wrapping the trunk with a collar of heavy paper, duct tape, or fabric tree wrap and coating this with the sticky material. Check the coating every one or two weeks and stir it with a stick to prevent the material from getting clogged with debris and dead ants, which will allow ants to cross. Ant stakes with bait can also be used around trees.
If ants can be thoroughly washed away and excluded from an area, indoor insecticide sprays aren't necessary. Vacuuming up ant trails or sponging or mopping them with soapy water may be as effective as an insecticide spray in temporarily removing foraging ants in a building. Soapy water removes the ant's scent trail, especially if thorough cleaning is done at the entry points. Some soap products such as window cleaners can kill ants on contact but leave no residual toxicity. Certain plant-based oils (e.g., peppermint, rosemary, clove, orange, and thyme) are formulated in pesticide-type products to be applied for this purpose, although as food-based products they aren't required to be registered as pesticides. These types of products typically provide excellent contact activity but have limited residual activity against ants.
A common practice used to prevent ants from coming indoors is to apply a perimeter treatment of residual sprays around the foundation. Commonly used insecticides include the pyrethroids bifenthrin, cypermethrin, and lambda-cyhalothrin. All are available in retail products, but products available to professionals provide longer residual control than home-use products.
Spraying around the foundation won't provide permanent control, because it kills only foraging ants without killing the colony and the queens. Typically the foragers represent only a small proportion of the colony. On occasion, barrier sprays make the situation worse by trapping ants indoors. Perimeter treatments may appear to knock down the population, but ants will quickly build back up and invade again.
To try to achieve long-term control, some pest control companies offer every-other-month perimeter spray programs. Perimeter treatments pose more risk of environmental upset than baits in bait stations and are less effective than a bait-based IPM program. Because of water quality concerns, the California Department of Pesticide Regulation has recently adopted regulations limiting the use of perimeter treatments with pyrethroid insecticides.