In the Bay Area, the most frequently found ants populating our gardens and invading our homes are Argentine ants. Argentine ants are small (1/8”), and their queens are slightly larger. Their bodies are constricted, giving them an appearance of a thin waist, which distinguishes them from termites.
Although we often think of them as pests, ants provide an ecological cleansing and fertilization service of considerable importance. They kill and eat many pest insects, aerate the soil, and recycle dead animal and vegetable material. The best approach to ant management is to keep them outdoors.
Category
Insect
Signs/Symptoms
Look for individual “scouts” searching for food, water sources, or pet food bowls. Eliminate the scouts and thoroughly clean the area where they traveled and left a pheromone trail to signal others to follow. If a long line of ants is marching your way, vacuum them up or spray ants with soapy water and wipe up with a sponge.
Where
Ants alternately seek food, sometimes sweet, sometimes savory, warmth or shade, water, or shelter from rain. They change their preferences frequently. Ants are attracted to honeydew, a sugar-rich, sticky liquid secreted by aphids, scale, mealybugs, and other insects that feed on plant sap. Ants “farm” these honeydew-producing insects, often increasing damage from these pests. Ants usually nest in soil next to buildings that are close to food sources or in shallow mounds outdoors that harbor honeydew producing insects.
When
Ants are most likely to enter homes in cold wet conditions, typically in the winter. Hot dry conditions motivate the ants to find cool shady spaces.
Prevent
In the garden: Use sticky barriers such as Tanglefoot around the trunk of trees or bushes to prevent access to honeydew producing insects. Prune any branches that touch walls, fences or the ground to prevent ants from finding an accessible route to the plant.
Meticulous housekeeping eliminates significant ant problems by removing needed resources. Remove trash immediately. Caulk holes, crevices, or cracks in foundations or walls that provide entry points to buildings. Weather strip doors and windows.
Store food in containers that seal tightly or in the refrigerator. Keep everything clean and dry and repair any leaking faucets. Clean pet bowls regularly.
Manage
Ant baits contain a pesticide mixed with an attractive food substance. Ants take small quantities of the bait back to the nest to share. The entire nest can sometimes be eliminated.
Use baits with boric acid, hydramethylnon, fipronil, or arsenic as an active ingredient. Keep several baits on hand as Argentine ants change their food preference frequently. If one bait is not working, try another. Do not spray insecticide around the bait. When ants are gone, remove the bait. Put the bait in its original box, insert in a plastic bag, seal, and save to use again. Keep baits away from children and pets.
Baits may take several weeks to kill the ants. At first you may see more ants coming to the bait, but after a few days to a week you should see a significant reduction.
If ants are nesting in an indoor potted plant, take it outdoors. Place it in a bucket filled with water that comes an inch below the rim of the pot. Use a stick to create a bridge for the ants to get out of the pot without getting in the water. When no more ants emerge, drain the pot and return it to the house.
