Households frequently encounter ants as one of the most widespread pests. These tiny creatures can be found in various settings like restaurants, hospitals, offices, warehouses, and other structures where they can locate sources of food and water. In addition to this, ants engage in a symbiotic relationship with honeydew-producing insects such as aphids, soft scales, whiteflies, and mealybugs, often found on both outdoor and indoor plants. Unfortunately, this association leads to increased harm caused by these pests. Nonetheless, ants also play crucial roles in the ecosystem. They act as natural predators, consuming pests like fleas, caterpillars, and termites, as well as scavenging on dead insects and decomposing tissue from deceased animals.
Worldwide, there are more than 12,000 ant species. In California alone, approximately 200 species exist, yet only a small fraction of them, less than twelve, are significant pests (see Table 1). Among the most prevalent ant species in California households and gardens is the Argentine ant (Linepithema humile, formerly Iridomyrmex humilis). Other common ant pests include the pharaoh ant (Monomorium pharaonis), the odorous house ant (Tapinoma sessile), the thief ant (Solenopsis molesta), and the southern fire ant (Solenopsis xyloni). The velvety tree ant (Liometopum occidentale), which nests in old wood, is also a frequently encountered outdoor species in landscapes.
Although less widespread, the red imported fire ant (Solenopsis invicta) has recently established itself in southern California and is considered of significant concern. However, the spread of the fire ant has been somewhat impeded in certain areas due to competition from the Argentine ant.
Carpenter ants (Camponotus spp.) are another type of ant that infiltrates buildings in California. While they do not consume wood like termites, they excavate it to create nests, potentially causing substantial damage.
Worldwide, there are more than 12,000 ant species. In California alone, approximately 200 species exist, yet only a small fraction of them, less than twelve, are significant pests (see Table 1). Among the most prevalent ant species in California households and gardens is the Argentine ant (Linepithema humile, formerly Iridomyrmex humilis). Other common ant pests include the pharaoh ant (Monomorium pharaonis), the odorous house ant (Tapinoma sessile), the thief ant (Solenopsis molesta), and the southern fire ant (Solenopsis xyloni). The velvety tree ant (Liometopum occidentale), which nests in old wood, is also a frequently encountered outdoor species in landscapes.
Although less widespread, the red imported fire ant (Solenopsis invicta) has recently established itself in southern California and is considered of significant concern. However, the spread of the fire ant has been somewhat impeded in certain areas due to competition from the Argentine ant.
Carpenter ants (Camponotus spp.) are another type of ant that infiltrates buildings in California. While they do not consume wood like termites, they excavate it to create nests, potentially causing substantial damage.
Damage
Within buildings, household ants have a preference for consuming sugars, syrups, honey, fruit juice, fats, and meat. Their foraging trails, consisting of thousands of ants, can cause significant concern among occupants as they lead from nests to food sources. Outdoors, ants are attracted to the sweet honeydew produced by soft scales, mealybugs, and aphids. This sugary liquid, which serves as their excrement, contains nutrients and sugars. Unfortunately, outbreaks of scales and aphids can frequently occur when ants tend to them for honeydew, as the ants provide protection to these pests against their natural predators.
While most ant species rarely bite, they possess pincer-like jaws capable of delivering a bite. However, the velvety tree ant stands out as an aggressive biter. A few ant species are equipped with stingers, including native fire ants and harvester ants, primarily found outdoors, and they represent the most common stinging ants in California. Recently, the invasive and aggressive red imported fire ant (Solenopsis invicta) has been discovered in several southern California counties. If you suspect an infestation of fire ants, it is important to report it to your county agricultural commissioner.
Management
Effectively managing ants requires consistent and dedicated efforts, utilizing a combination of mechanical, cultural, sanitation, and often chemical control methods. Completely eradicating ants from outdoor areas is neither realistic nor practical. Instead, it is advisable to focus on preventing ants from entering buildings or damaging valuable plants, while also eliminating their sources of food and water. Minimizing the presence of outdoor ant populations near structures can help reduce the likelihood of ants making their way indoors. However, it is important to recognize that ants can have beneficial effects in garden environments. Familiarize yourself with the seasonal patterns of ants in your area and proactively take measures such as caulking and baiting to address potential annual invasions. It's crucial to note that different species of ants may respond differently to various management practices, so adapting strategies accordingly is key.
Regularly monitor areas with attractive food sources or moisture for any signs of ants. These tiny creatures can invade various spaces such as kitchens, bathrooms, offices, or bedrooms. Conduct thorough inspections beneath sinks, inside cupboards, along pipes, and adjacent to electrical wires. Keep an eye out for noticeable trails of ants or even a few individual ants. The presence of solitary ants suggests scouting behavior, where they randomly search for food or suitable nesting sites. If you observe ant trails, make an effort to track their movement, identifying the entry point into the building and, if possible, locate the nest. Pay attention to any holes or cracks in foundations or walls that could serve as potential entry points for ants.
To prevent ants from entering buildings, seal cracks and crevices around the foundations that serve as entry points from the outside. Consider using professional-grade caulking products that contain silica aerogel for long-lasting control and pyrethrins for more immediate effects. Ants tend to follow structural elements like wires and pipes, using them as trails to access and navigate within buildings. Eliminate cracks and crevices indoors, especially in areas such as kitchens where food is prepared and stored.
Store enticing food items like sugar, syrup, honey, and pet food in tightly sealed containers, ensuring the outer surfaces of the containers are clean. Rinse and remove empty soda containers from the premises. Thoroughly clean up grease and spills. Regularly remove garbage from buildings and replace liners frequently. Be vigilant for indoor nesting sites, such as potted plants. If ants are found in potted plants, take the containers outside and immerse them in a solution of insecticidal soap and water for at least 20 minutes. Use a mixture of one to two tablespoons of insecticidal soap per quart of water, ensuring the solution covers the surface of the soil.
Outdoor ant nests are often associated with plants that harbor large populations of honeydew-producing insects, such as aphids, soft scales, mealybugs, or whiteflies. Avoid planting such trees and shrubs near buildings or effectively manage the honeydew-producing insects. Keep plants, grass, and mulch several inches away from the building's foundation to eliminate potential nesting sites for ants.