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Pest Profiles - Invertebrates


  • About

    Argentine ant
    Argentine ant
    Prevalent household pest in households.. Most common outdoor ants in California are Argentine ants. Body is constricted, giving appearance of a thin waist, which distinguishes it from termites. Adults, known as workers, are wingless. Pharaoh ants are found indoors. Carpenter ants damage wood structures. Colors include brown, yellow, black.

  • Category
  • Signs/Symptoms

    Long trails of ants leading from nests to food sources. Ants crawling over exposed food or a pet food bowl. Stray ants on counters. Ants are more of at most a nuisance than a significant pest.

  • Where

    Ants enter buildings seeking food, water, warmth, shelter, or refuge from dry, hot weather or flooded conditions. Outdoor ants are attracted to honeydew that soft scale, mealybugs and aphids produce. They protect these honeydew-producing insects, which increases damage from these pests in the garden. Ants usually nest in soil next to buildings which 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. In Northern California, this is typically in the winter with a smaller peak during hot, dry conditions, often in August and September. Treatments are most effective when made in late winter and early spring when ant populations are just beginning to grow. 

  • Prevent

    In the garden: Band tree trunks with sticky substances such as Tanglefoot. Trim branches to keep ants from reaching structures or plants. Remove access to nesting sites and conditions conducive to nesting and entry.

    Meticulous housekeeping eliminates significant ant problems by removing needed resources. Caulk holes, crevices, or cracks in foundations or walls that provide entry points to buildings. 

    Follow ant trails to their entry point and to the nest, when possible.

    Store food items like sugar, syrup, honey and pet food in closed containers.  Clean up grease, spills and remove trash and recycling immediately.

  • Manage

    Use baits primarily outdoors, spacing every 10 to 20 feet around foundation and at nest openings. The most effective baits for Argentine ants are borate-based. Gel formation of pesticide baits can be applied to small cracks and crevices.

    Use baits indoors only if there is a serious infestation. Baits in refillable bait stations contain a slow-acting insecticide. Ants who are foraging can feed bait to the whole colony before they die. Keep baits away from children and pets.  

    Take potted plants infested with nesting ants outdoors.  Submerge infected pots in a solution of one to two tablespoons of insecticidal soap per quart of water.  Allow solution to cover the soil for 20 or more minutes. Clean infested areas with soapy water or window cleaners.   


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