Ants are among the most prevalent pests in households. Ants also invade restaurants, hospitals, offices, warehouses, and other buildings where they can find food and water. On outdoor and sometimes indoor plants, ants protect and care for honeydew-producing insects such as aphids, soft scales, whiteflies, and mealybugs, increasing damage from these pests. Ants also perform many useful functions in the environment, such as feeding on other pests (e.g., fleas, caterpillars, and termites), dead insects, and decomposing tissue from dead animals.
More than 12,500 of an estimated total of 22,000 species of ant have been classified. They are easily identified by their elbowed antennae and the distinctive node-like structure that forms their slender waists.
Inside buildings, household ants feed on sugar, syrup, honey, fruit juice, fats, and meat. Long trails of thousands of ants may lead from nests to food sources, causing considerable concern among building occupants. Outdoors ants are attracted to honeydew that soft scales, mealybugs, and aphids produce. This liquid excrement contains sugars and other nutrients. Frequently outbreaks of scales and aphids occur when ants tend them for honeydew, because the ants protect scales and aphids from their natural enemies.
Ants can bite with their pincerlike jaws, although most species rarely do. However, the velvety tree ant is an aggressive biter. A few ants sting, including native fire ants and harvester ants, which are primarily outdoor species and are the most common stinging ants in California. An aggressive stinging ant, the red imported fire ant has been found in various Southern California counties. If you suspect a fire ant infestation, report it to your county agricultural commissioner. For more information about red imported fire ants, see Pest Notes: Red Imported Fire Ant.
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.
Remember that ants often play a beneficial role in the garden. Become aware of the seasonal cycle of ants in your area and be prepared for annual invasions by caulking and baiting before the influx. Different species of ants respond to management practices differently. For management information specific to a particular species, see the Key to Identifying Common Household Ants. See also the videos related to ant management in the home.
Bed bugs, bed-bugs, or bedbugs are parasitic insects of the cimicid family that feed exclusively on blood. Cimex lectularius, the common bed bug, is the best known, as it prefers to feed on human blood.
The name "bed bug" derives from the preferred habitat of Cimex lectularius: warm houses and especially nearby or inside of beds and bedding or other sleep areas. Bed bugs are mainly active at night, but are not exclusively nocturnal. They usually feed on their hosts without being noticed.
There are six species of cockroaches can become pests: German cockroach, brownbanded cockroach, oriental cockroach, smokybrown cockroach, American cockroach, and Turkestan cockroach. A seventh species, the field cockroach, is not really a pest. It is usually found outdoors, but sometimes comes indoors when it is hot or dry and is often mistaken for the German cockroach. Of these seven species, the one that has the greatest potential for becoming persistent and troublesome is the German cockroach, which prefers indoor locations. Oriental and American cockroaches occasionally pose problems in moist, humid areas.
Cockroaches may become pests in homes, schools, restaurants, hospitals, warehouses, offices, and virtually in any structure that has food preparation or storage areas. They contaminate food and eating utensils, destroy fabric and paper products, and impart stains and unpleasant odors to surfaces they contact.
People are repulsed when they find cockroaches in their homes and kitchens. Cockroaches (especially the American cockroach, which comes into contact with human excrement in sewers or with pet droppings) may transmit bacteria that cause food poisoning (Salmonella spp. and Shigella spp.). German cockroaches are believed to be capable of transmitting disease-causing organisms such as Staphylococcus spp., Streptococcus spp., hepatitis virus, and coliform bacteria. They also have been implicated in the spread of typhoid and dysentery. Indoor infestations of cockroaches are an important source of allergens and risk for asthma among some populations. The levels of cockroaches and allergens are directly related to cockroach density, housing disrepair, and sanitary conditions.
Managing cockroaches is not easy. You must first determine where the roaches are located. The more hiding places you locate and manage, the more successful your control program will be. Remember that cockroaches are tropical and most like warm hiding places with access to water. Some locations may be difficult to get to. Reduction of food and water sources and hiding places is essential. If cockroaches have access to food, baits (which are a primary control tool) have limited effect. Sprays alone will not eliminate cockroaches. An IPM approach that integrates several strategies is usually required.
If you know the species of cockroach, you will be better able to determine where the source of infestation is and where to place traps, baits, or insecticides. Note locations of suspected infestations and concentrate control and preventive measures in these areas. The keys to controlling cockroaches are sanitation and exclusion: cockroaches are likely to reinvade as long as a habitat is suitable to them (i.e., food, water, and shelter are available), so the conditions that promoted the infestation must be changed. In addition to sanitation and exclusion, baits can be effective against most species of cockroaches. Pesticide spray products are registered for use on cockroaches and may temporarily suppress populations, but they usually do not provide long-term solutions and are not generally recommended. Commercially available devices that emit ultrasound to repel cockroaches are not effective.
Of the thousands of species of flies, only a few are common pests in and around the home. Some of the more common nuisance flies are the house fly (Musca domestica), the face fly (Musca autumnalis), the stable fly (Stomoxys calcitrans), the little house fly (Fannia canicularis), and several species of garbage fly (especially in the genus Phaenicia). These pests breed in animal wastes and decaying organic material from which they can pick up bacteria and viruses that may cause human diseases. In addition, adult stable flies (sometimes called "biting flies") feed on mammalian blood and can give a painful bite.
All flies undergo complete complete metamorphosis with egg, larva, pupa, and adult stages in their development. The female fly deposits her eggs in animal waste or moist organic material where the larvae, or "maggots," complete their development, feeding on bacteria associated with their developmental site. When the maggots have completed their development and are ready to undergo the next step in their metamorphosis, they convert their last larval skin into a puparium, a hardened shell within which the pupa develops. Within the puparium, the pupa transforms into an adult fly, which pops off the end of the puparium and emerges. Body fluids pump into the fly's veins, causing the wings to unfold and expand and allowing them to dry and harden so that the adult can fly. The rate of fly development is dependent upon temperature, and under optimal summertime conditions flies may develop from egg to adult in as little as 7 days. Once the female fly has mated, she can lay several batches of eggs, typically containing over 100 eggs each.
Because they have sponging mouthparts, house flies cannot bite; however, they may play an important role in disease transmission to humans and animals. House flies serve as carriers of disease agents due to their predilection for feeding on animal wastes, garbage, and human foods. House flies are known to carry bacteria and viruses that cause conditions such as diarrhea, cholera, food poisoning, yaws, dysentery, and eye infections.
Flies found inside a building have entered from the outside in almost all cases. Therefore, barriers preventing access to the building are the first line of defense. Cracks around windows and doors where flies may enter should be sealed. Well-fitted screens will also limit their access to buildings. Outdoors, regular removal (at least once a week) and disposal of organic waste, including dog feces and rotting fruit, reduces the attractiveness of the area to adult flies and limits their breeding sites. Garbage should not be allowed to accumulate and should be placed in plastic bags and held in containers with tight-fitting lids. Garbage should also be placed as far from a building entrance as is practicable. In general, poor exclusion and lack of sanitation are the major contributors to fly problems.
Sticky fly papers or ribbons are effective at eliminating a few flies in relatively confined areas, but are not effective enough to manage heavy infestations or to provide control in an outdoor setting. Inverted cone traps containing fly food attractants can be readily purchased commercially and are effective when they are not competing with nearby garbage or animal wastes. The fly food attractants used in these inverted cone traps will be quite foul smelling, so the traps should be placed at some distance from occupied structures. Fly traps using ultraviolet light may be effective when used indoors where they are not competing with daytime sunlight. For control of just a few flies, the time-tested fly swatter is appropriate. Don't use fly swatters near food preparation areas because they may result in contaminating food with insect body parts.
Selective use of insecticides against house flies is one component of a total fly management program, but should only be used after all possible nonchemical strategies have been employed. In most home situations, pesticides are not needed or recommended. Sanitation methods along with screens to keep flies out of the home should be sufficient. If sanitation efforts are not possible, a nonresidual pyrethrin aerosol may be used. Outside, a professional pest control company can be hired to apply residual insecticides to surfaces such as walls and overhangs that are being used by the flies as resting areas. Fly baits used in trash areas may be effective in reducing the number of adult flies if proper sanitation practices are followed. However, when flies have access to garbage, baits will not control them.
Mosquito adults are small, delicate, two-winged flies. At first you might mistake them for the widely distributed, nonbiting midges. However, female mosquitoes differ from similar insects because of their long, slender proboscis, a tubular feeding organ adapted for piercing skin and sucking blood.
If you were to view a mosquito with a hand lens, you would see another characteristic that distinguishes mosquitoes from closely related flies-small scales cover their long, slender wings. Male mosquitoes also have scale-covered wings, but they use their proboscises, or "beaks," only for sucking plant juices and other sources of sugar rather than blood.
Mosquito larvae, or wigglers, usually are black or brown and occur in stagnant or nearly still water in surface pools, tree holes, or man-made containers such as abandoned tires. Culex and Aedes larvae have a distinctive siphon, or air tube, at the rear of their bodies, which is lacking in Anopheles. The next immature stage, the pupa, or tumbler, is aquatic, small, comma-shaped, and usually a dark color.
Female mosquitoes of nearly all species require blood from vertebrate animals such as people, pets, and livestock. The most important consequence is the acquisition and later transmission of microorganisms that cause diseases including Western equine encephalomyelitis, St. Louis encephalitis, and West Nile encephalitis. These viruses can cause serious, sometimes fatal, neurological ailments in people. Western equine encephalomyelitis and West Nile viruses also can affect horses and occasionally other domestic animals.
Most people infected with viruses that mosquitoes transmit show no symptoms or only mild, flulike ones. However, severe symptoms following infection occur in a small percentage of people. Western equine encephalomyelitis infections tend to be more serious in infants, whereas St. Louis encephalitis affects older people. West Nile Virus infections can range in severity from no detectable symptoms to West Nile fever to comparatively severe neuroinvasive diseases such as West Nile encephalitis, West Nile meningitis, or West Nile meningoencephalitis. For more information, see the sidebar on West Nile Virus.
Some Anopheles mosquitoes found in California can transmit human malaria. If these mosquitoes suck the blood of a person who has malarial parasites, the insects can pass on the infection when they bite other people. Endemic malaria was eradicated from California by the 1940s; however, travelers have constantly reintroduced the parasite, which has led to several small outbreaks.
Mosquitoes also can vector, or carry, dog heartworm in California. Oak trees, common in the foothill areas of the state, provide tree holes that fill with water and harbor the larvae of the principal Aedes vector of this disease. Even when mosquitoes don't transmit the causative agents of infectious diseases, they can be a serious nuisance and a health problem to people and livestock. Mosquito bites can result in secondary infections, allergic reactions, pain, irritation, redness, and itching.
The objective of mosquito management is to keep populations below levels where they become a nuisance or a public health problem leading to an outbreak of disease. Mosquito management often occurs on an areawide basis by public agencies that either are part of local health departments or are independent districts organized specifically for mosquito control. California has more than 60 mosquito and vector control districts. Some are small and have responsibility for mosquito abatement in a few hundred square miles, while the activities of others can encompass one or two entire counties.
Vector control technicians search out mosquito larvae in standing water and use appropriate control measures that are cost-effective and environmentally friendly. Control measures include environmental manipulation to reduce aquatic habitats such as removing dense patches of decaying vegetation conducive to mosquito production, applying mosquito-specific control agents, and stocking fish that feed on the larvae. Many materials currently in use are biological in origin and are highly specific for mosquitoes while having little or no effect on other organisms.
Controlling irrigation water in agricultural areas to avoid excess runoff also is an important mosquito control method. However, eliminating natural bodies of water such as vernal pools that also serve as wildlife habitat has ceased to be a mosquito control option because of habitat preservation concerns. Occasionally mosquito abatement agencies also might have to use chemical pesticides to kill adult mosquitoes, but ordinarily this occurs only when adult populations become so large they cause extreme annoyance to many people or when the threat to people of an outbreak of a disease-causing pathogen is high.
Rats are some of the most troublesome and damaging rodents in the United States. They eat and contaminate food, damage structures and property, and transmit parasites and diseases to other animals and humans. Rats live and thrive in a wide variety of climates and conditions and are often found in and around homes and other buildings, on farms, and in gardens and open fields.
People don't often see rats, but signs of their presence are easy to detect. In California, the most troublesome rats are two introduced species, the roof rat and the Norway rat. It's important to know which species of rat is present in order to choose effective control strategies.
Rats, like house mice, are active mostly at night. They have poor eyesight, but they make up for this with their keen senses of hearing, smell, taste, and touch. Rats constantly explore and learn, memorizing the locations of pathways, obstacles, food and water, shelter, and features of their environment. They quickly detect and tend to avoid new objects and novel foods. Thus, they often avoid traps and baits for several days or more following their initial placement. While both species exhibit this avoidance of new objects, this neophobia is usually more pronounced in roof rats than in Norway rats.
Rats eat and contaminate foodstuffs and animal feed. They also damage containers and packaging materials in which foods and feed are stored. Both rat species cause problems by gnawing on electrical wires and wooden structures such as doors, ledges, corners, and wall material, and they tear up insulation in walls and ceilings for nesting.
Norway rats can undermine building foundations and slabs with their burrowing activities and can gnaw on all types of materials, including soft metals such as copper and lead, as well as plastic and wood. If roof rats are living in the attic of a residence, they can cause considerable damage with their gnawing and nest-building activities. They also damage garden crops and ornamental plantings.
Among the diseases rats can transmit to humans or livestock are murine typhus, leptospirosis, salmonellosis (food poisoning), and ratbite fever. Plague is a disease that both roof and Norway rats can carry, but in California it is more commonly associated with ground squirrels, chipmunks, and native woodrats.
Termites comprise a large and diverse group of ecologically and economically important insects that feed on cellulose, principally in wood. Worldwide there are over 2,600 species of termites; in California there are at least 23 different species. Although many people associate termites with negative impacts, in nature they make many positive contributions to the world's ecosystems.
Termites can be highly beneficial as they degrade woody debris, return nutrients to the soil, and provide an energy-rich food source to a variety of predators. Their tunneling efforts help to ensure that soils are porous, contain nutrients, and are healthy enough to support plant growth. Termites rarely injure or kill trees. However, a minority of termite species can be very destructive to wood in buildings, including furniture and many other wood-based products. Each year thousands of housing units in California require treatment for the control of these insects.
Although termites are ecologically beneficial in that they break down detritus to add nutrients to soil, the same feeding behaviors that prove helpful to the ecosystem can cause severe damage to human homes. Because termites feed primarily on wood, they are capable of compromising the strength and safety of an infested structure. Termite damage can render structures unlivable until expensive repairs are conducted.
Structural property damage Homes constructed primarily of wood are not the only structures threatened by termite activity. Homes made from other materials may also host termite infestations, as these insects are capable of traversing through plaster, metal siding and more. Termites then feed on cabinets, floors, ceilings and wooden furniture within these homes.
Drywood termite damage Drywood termites build their colonies within wooden structures on which they feed. They can be found inside of walls or furniture. Drywood termite infestations may only become apparent after a colony has burrowed so deeply into an infested item that the veneer cracks and the maze-like tunnels beneath become visible. Such damage is common in antique furniture pieces. Should this occur on new furniture or the floors or walls of your home, contact a pest control professional to discuss the severity of your infestation, as well as extermination options.
It is unlikely that homeowners will be able to execute subterranean termite control on their own. However, it is important for homeowners to have some familiarity with inspection procedures, reduction of conducive conditions, and treatment strategies. Successful termite management requires special skills and knowledge, including a working knowledge of building construction. An understanding of termite biology and identification can help a homeowner understand and select a suitable method of control. Of course, homeowners can replace termite damaged wood and correct conditions conducive to subterranean termite infestation on their own; however, applications of registered pesticides are highly regulated and require a licensed pest control professional to carry out the inspection and control program.
Multiple colonies of the same termite species or several different species can infest a building. A professional inspection and an integrated approach to control are required. A combination of methods, such as habitat modification, elimination of excess moisture, removal of infested wood from the structure, exclusion of termites from the building by physical and/or chemical means, and the use of chemical methods to destroy existing colonies will probably be necessary.