WW-06269     Reviewed 1999  

Environmentally Conscious Methods of
Pest Control In and Around Homes

Copyright ©  2012  Regents of the University of Minnesota. All rights reserved.

Pesticides are substances or a mixture of substances used for destroying, preventing, repelling or mitigating pests. Pesticides also include substances used as plant growth regulators, defoliants, and desiccants. Substances derived from plants, microorganisms, and organic or inorganic molecules are included under the broad definition of pesticides. Pesticides used against insects are called insecticides; those used against weeds, fungi, rodents, and birds are called herbicides, fungicides, rodenticides, and avicides, respectively.

Pesticides are commonly used in and around homes^* because they are easy to apply, fast-acting, and effective against a wide variety of pests. A 1990 nationwide survey by Research Triangle Park, North Carolina, showed that 85% of homeowners store at least one or more household pesticide products. A 1979 United States Environmental Protection Agency survey estimated that about 87 million pounds of pesticides are used annually in and around homes. About 43% and 32% of the 87 million pounds used were insecticides and herbicides, respectively; the remaining 25% consisted of fungicides, rodenticides, disinfectants, and other chemicals.

Insecticides are commonly used in and around homes because most homeowners consider insects and insect relatives (e.g., mites, spiders, centipedes, and millipedes) as pests or as a nuisance, especially if they occur indoors. A 1990 University of Minnesota survey of 440 home dwellers in Minnesota indicated that about 65% tolerated insects found outdoors and 26% disliked insects. Conversely, about 81% of the same home dwellers surveyed disliked indoor insects, and only 13% indicated any tolerance toward insects inside their homes.

Pests found in and around homes

Insects and insect relatives frequently encountered outdoors in Minnesota are: ants, mosquitoes, spiders, bees, wasps, flies, black flies, centipedes, carpenter ants, millipedes, sowbugs, pillbugs, boxelder bugs, ticks, crickets, aphids, daddy-long-legs, and mites. Some of these same pests (e.g., spiders, sowbugs, millipedes, and centipedes) become a nuisance when they seek harborage indoors and cause concern to residents. In addition to the invertebrate pests listed above, including fleas and pantry pests (sawtoothed grain beetle, red flour beetle, rice weevil, and Indianmeal moth), vertebrates such as rodents, bats, and birds also become pests when they seek refuge indoors.

Both the invertebrate and vertebrate pests enter homes through openings in foundations and walls, and through open, unscreened or broken doors and windows. Some invertebrates are brought indoors on infested plant or food materials. If environmental and nutritional requirements for these pests are not met indoors, they may perish. Other species may thrive indoors because of stable and suitable environmental conditions, abundant availability of food, and absence of natural enemies. Some species enter homes to escape unfavorable environmental conditions outdoors. For instance, boxelder bugs, cluster flies, and elm leaf beetles overwinter indoors until conditions outdoors become conducive for their survival.

Reasons for pest control

Homeowners apply control measures against outdoor and indoor pests because they dislike the presence of pests, prefer to maintain a pest-free property, and want to eliminate pests that transmit diseases (e.g., cockroaches, ticks, flies, etc.). Several chemical and nonchemical approaches are effective in controlling pests outdoors and indoors. However, nonchemical methods are now becoming popular because of the public's concern about the effects of pesticides on humans, animals, and the environment. The use of pesticides may lead to the development of resistance in pests, resulting in ineffective control at recommended label rates. Several simple nonchemical methods, if used properly, can effectively reduce pest incidence and abundance in and around homes. In this article, we give an overview of some simple environmentally compatible nonchemical, chemical, and biological pest control strategies.

Nonchemical methods of pest control

The range of nonchemical options available may vary with the pest species, pest intensity or severity, and effectiveness of the option. Several key nonchemical options that may help reduce the amount of pesticides used in and around homes are listed below. However, it is important to realize that for effective use of nonchemical methods, an understanding of pest biology, ecology, and behavior is essential. Such an understanding is not always required when using synthetic pesticides.

Exclusion: Any measure used to prevent entry of organisms indoors through openings in the building structure, doors, windows, or on infested plant or food materials. Some techniques include screening openings to prevent entry of flies, mosquitoes, and beetles; caulking cracks and crevices to remove existing or potential harborages of pantry pests and cockroaches; and sealing or repairing exterior openings to prevent entry of bats, mice, bees, and wasps. Plants and food products must be carefully inspected for infestations at the time of purchase and before they are brought indoors.

Sanitation: Maintaining clean surroundings both outdoors and indoors removes potential areas where pests can feed, breed, and hide. Sanitary measures include: disposing of garbage on a weekly basis during warm weather to control filth flies and cockroaches; discarding overripe fruits to control fruit flies and fungus beetles; removing bird nests as these harbor dermestids, clothes moths, mites, and lice; and vacuuming to reduce populations of fleas, carpet beetles, house dust mites, and several ground-dwelling insects and insect relatives. It is also important to keep kitchen areas clean to reduce incidence of pantry pests and cockroaches.

Habitat modification: Includes any method used to eliminate or disrupt areas where pests reside. For example, removing weeds and keeping well-mowed lawns reduces incidence of crickets and ticks. Removing debris and fallen leaves near foundations reduces sowbug and centipede populations. Wood or wooden piles, where carpenter ants, ground beetles, and spiders seek harborage, must be stored away from structures. Creating a vegetation-free barrier around the perimeter of the building will reduce incidence of many ground-dwelling pests such as clover mites. The use of dehumidifiers is recommended, especially in basements, to create and maintain a dry environment to discourage incidence of sowbugs, centipedes, firebrats, and house dust mites.

Temperature control: Artificially manipulating the temperature of substrates infested by pests or areas where pests reside is an inexpensive nonchemical strategy. The time from treatment to death of a pest and numbers of the pest killed, may vary with the pest stage, temperature, and duration of exposure. Pantry pests, clothes moths, and carpet beetles can be eliminated by subjecting infested foods, clothes, and carpets, respectively, to extremely hot or cold temperatures. In general, all developmental stages of pantry pests, clothes moths, and carpet beetles can be killed within minutes to hours when exposed to temperatures below 32° F and above 104° F.

Mechanical control: A rolled newspaper or magazine and fly swatters are some tools used for killing visible and less mobile or immobile pests. On infested plants, hand-picking insects (e.g., hornworms) is a partially effective means of pest control. Infested leaves must be excised from plants, bagged, and discarded.

Traps: Traps are escape-proof devices that capture highly mobile and active pests. Live traps can be used for rabbits, pocket gophers, and squirrels. Unbaited sticky traps such as red spheres, resembling apples, are useful for trapping apple maggot adults. Colored (yellow) sticky traps are effective in capturing whiteflies and aphids. Sticky traps can be baited with commercial lures (pheromones and food attractants) to enhance trap catch. For example, sticky traps baited with lures for pantry pests, wasps, and flies are commercially available.

Traps are useful for early detection and continuous monitoring of infestations. They are not effective in reducing populations unless the pest population is isolated or confined to a small area. The chance of detecting the presence of pests in a given area is related to the number of traps used. Therefore, when pests are present in very low numbers, it is advantageous to use more than a few traps. Pests must be active or mobile to be captured in traps. Therefore, any environmental variable (temperature, humidity, wind, light, or food) or biological factor (age, sex, mating status, etc.) that influence pest activity, affects trap catch. Consequently, absence of pests in traps does not imply that the pests are not present in the sampled area.

Diatomaceous earth (DE): Several DE formulations are commercially available. These products contain fossilized siliceous (silicon-containing) skeletons of aquatic diatoms (algae) of various shapes and sizes (<1 to 34 microns). DE formulations predominantly are made up of noncrystalline or amorphous silicon dioxide. Although the exact mode of action of DE products is not known, it is believed that DE kills insects and insect relatives by absorbing and abrading the water-proofing, waxy outer covering of the skin (cuticle). Absorption and abrasion to the waxy layer of the cuticle leads to water loss and subsequently death due to dehydration. DE products are most effective on soft-bodied insects or insect relatives. Because the mode of action is mechanical, insects and insect relatives may not develop resistance to this natural product.

Biological control agents: Parasitic and predatory insects, mites, and nematodes are now commercially available to control pests. For example, lacewing larvae and ladybird beetle larvae and adults are predators of aphids. Parasitic and predatory organisms should be used only where pesticides are discontinued or were not previously used, because these beneficial organisms are highly susceptible to pesticides. The degree of control achieved with the use of beneficial organisms is variable, and the cost-effectiveness for many beneficials has not been well-documented.

Three different varieties of the bacteria Bacillus thuringiensis are available to control larvae of moths and butterflies (caterpillars), mosquitoes and black flies (maggots), and beetles (grubs). The varieties kurstaki, israelensis, and san diego are effective against caterpillars, maggots, and grubs, respectively. The larvae succumb to the bacterial toxin after ingesting or consuming the treated substrate. For controlling Japanese beetle grubs on lawns, the use of Bacillus popillae may offer some control. Recent evidence suggests that caterpillars can develop resistance to the B. thuringiensis toxin.

Miscellaneous techniques: Pantry pests have the ability to puncture and penetrate paper and cardboard materials. Therefore, storing cereal and cereal products in tight plastic or tupperware containers instead of the original paper or cardboard holders prevents infestation by pantry pests. In order to avoid black flies, wear light-colored clothing that completely covers exposed areas of legs and hands. If mosquitoes are abundant outdoors, avoid outdoor activity. Dry cleaning clothes may eliminate clothes moth infestations.

Ultra sound devices and light traps are two nonchemical control measures that are ineffective in suppressing pest populations.

Biorational pesticides

For some pests, nonchemical techniques do not exist or are ineffective. In such cases, the use of chemical pesticides may be necessary. Pesticides that are rational alternatives to conventional pesticides are termed "biorationale". The biorational products offer comparable control efficiency with the benefit of reduced hazards to humans, pets, wildlife and the environment. Several groups of biorational pesticides are discussed below.

Insecticidal soaps: Soaps are sodium or potassium salts of fatty acids combined with fish or vegetable oils. These soap solutions have insecticidal value because when applied to soft-bodied insects or insect relatives, they penetrate the waxy outer protective layer (cuticle) and dissolve cell membranes. As a result, the cells collapse and leak, leading to dehydration and death. Safer's soap solution is a commercial formulation that is effective on aphids, caterpillars, fleas, mealybugs, scales, and whiteflies. The commercially available insecticidal soaps are highly refined and safe to use on most plants. Any household soap or laundry detergent can be used at a rate of ½ cup per gallon of water on soft-bodied insects such as mealybugs and aphids. However, these mixtures may harm plants.

Horticultural oils: Horticultural oils are highly refined petroleum-based oils. When applied directly on insects, the oils kill insects by asphyxiation (by clogging spiracles or exterior openings along sides of the insect body that facilitate breathing). Oils are effective on soft-bodied insects such as aphids and mealybugs. These products are safe to apply on many plant species.

Botanicals: Are essentially plant-derived chemicals. Some of the common botanicals are: pyrethrum, neem, ryania, red squill, derris, nicotine, rotenone, limonene, and sabadilla. Different botanicals have different modes of action, and some botanicals have multiple modes of action. For instance, the component most active against insects in neem is azadirachtin. Azadirachtin is an effective feeding or oviposition deterrent, and also disrupts normal development of insects. Some botanicals are as highly toxic as some synthetic pesticides. The rat oral LD_50S (lethal dose that kills 50% of test animals) of ryania, nicotine, red squill, and pyrethrum range between 0.7 to 200 mg of active ingredient per kg of rat body weight. According to the Environmental Protection Agency's toxicity category, pesticides with LD_50S in the range of 0-50 and 50-500 mg per kg are considered highly toxic and moderately toxic, respectively.

Baits: Consist of one or more food materials combined with a selective pesticide to kill pests. Boric acid (2 parts to 98 parts bait [jelly, peanut butter]) is effective in killing some types of ants. For pantry pests, the use of wheat germ plus mineral oil bait is effective in drawing insects out of their hiding places into the bait. The bait must be presented in a small shallow cup or a dispenser. The oil kills trapped insects by suffocation (by clogging spiracles).

Keys to successful pest control

Correct identification of the pest is the first step in control, because information on pest biology, ecology, and behavior can be easily obtained if the pest is known. Contact your local Cooperative Extension Service office if you need help in identifying a pest, and for additional information on the pest.

Most pest control methods work well at low pest population densities. Therefore, it is important to detect pest problems early. Careful visual inspections or the use of traps can help in early detection of infestations.

Many pests are susceptible to control measures at certain times in their lives. Therefore, control measures must be timed to target the most vulnerable stage of pests. For instance, the bacterial insecticide, B. thuringiensis variety kurstaki, is effective on younger caterpillars; the bacteria has no effect on eggs, pupae, and adults. Therefore, it is important to apply the bacteria when small-sized caterpillars are present on the foliage. Repeated applications may be necessary to obtain additional reductions in populations of the susceptible stage in the same or future generations.

Pesticides should be used only as a last resort. If pesticides are used, they should complement available nonchemical or biorational methods. Please follow label directions and rates when applying pesticides.

The combined use of nonchemical and chemical control tactics, with favorable economic, social, and environmental consequences is called Integrated Pest Management (IPM). The use of IPM practices for controlling pests in and around homes is important if we are to reduce introduction of pesticides into the environment. If we better understand and appreciate the creatures that live in and around our homes, we may be able to reduce pesticide use by being content with the degree of control attained by using nonchemical pest control methods.

Suggested Reading^**

Lifton, B. 1991. Bug busters. Avery Publishing Group, Inc., New York.

Olkowski, W., S. Daar and H. Olkowski. 1991. Common-sense pest control. The Taunton Press, Connecticut.

Bh. Subramanyam is Assistant Extension Entomologist & Coordinator of the Minnesota Pesticide Impact Assessment Program; R. P. Wawrzynski is Research Assistant, Urban and Landscape Entomology.

Produced by Communication and Educational Technology Services, University of Minnesota Extension.

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