Brochures
Household Pests
 Insects that buzz around us in the yard or invade our homes are often just a nuisance,
but some are damaging to our food or possessions. A few simple preventative
measures stop most problems before they begin. Even when pests do get in, there
is rarely a need to use pesticides around the house. The most effective pest
control is usually the simplest: remove their food supply and breeding sites.
This includes such steps as managing garbage so that it is less attractive,
cleaning up spilled food, especially pet food, and eliminating damp conditions
around the house. Sometimes, however, you may have to be a detective to find the
source of an infestation. Pests, such as clothes moths, carpet beetles and flour
moths, can breed in a mouse or squirrel nest, an old yellowjacket nest or a bird
nest, out of sight in a wall, an attic or the eaves.
Prevention
Seal cracks: The first defense is making sure pests don't get into the house. Crawling pests enter through cracks in or around the foundation or siding, while flying insects come in through open doors and windows. An annual inspection of the foundation and siding to caulk cracks (use good quality silicone sealant) is a good idea. Be particularly careful to seal around exterior plumbing and electrical outlets. Make sure that door thresholds have good weather stripping under them and that the door and windows seal well when shut. Check that screens on crawl space vents and attic vents are intact and sealed around the edges.
Use Screens: Window screens are excellent for keeping insects out of a house, but screen doors are not very effective. This is because flies and mosquitoes are attracted to people or food odors so they hang around outside screen doors and whisk inside every time the door is opened. Try to ventilate the house adequately without screen doors, at least on heavily used entrances. If screen doors are used, they should have strong spring closers that shut the door quickly and tightly.
Manage Lights: Good design and management of exterior lighting is important to prevent insect problems.
- Avoid leaving porch lights on all evening to collect a cloud of moths and other insects. Every time the door is opened, the insects swirling around the light are swept into the
house. Minimize the attraction time by turning porch lights on only when they
are needed. Sensor lights that switch on in response to motion are ideal because
they light the area for arriving guests, but switch off after a few minutes
(saves energy too).
- When designing the lighting around the exterior of a new home, don't put light fixtures
directly above the doors, especially over doors to decks or patios that might be
used a lot in the evening. Place flood or spot lights a few feet away from the
door and direct the light onto porches and stairs. This illuminates them safely,
while keeping the mesmerized insects away from the door.
- Use yellow bulbs in yard light fixtures; flies and moths are not as attracted to
yellow as they are to ordinary white light bulbs.
Manage Garbage: Keep garbage in sturdy, tightly covered containers and wash them out regularly. This
prevents flies from breeding and reduces the attraction for ants and other
insects. If the kitchen food garbage can be composted daily, the trash will
contain little that is attractive to insects. Where composting is not possible,
tightly wrap up kitchen garbage, take it out frequently to a covered trash can,
and dispose of it in sealed plastic bags. Avoid letting old clothes, newspapers
and other trash accumulate in storage rooms, garages, etc., as these provide
breeding sites for many household pests.
Controls
Sticky Traps: Old-fashioned fly papers are widely available and effective at trapping flies, especially after a few flies have been caught on the strip. Hang them where people won't accidentally run into them and where any gummed up flies that might fall off won't land on carpets or where food is prepared.
Light Traps: Never use electrocutor or black-light insect traps outdoors. These don't attract mosquitoes, but do kill many beneficial insects. They are designed for use indoors in restaurants, dairies and industrial buildings and rarely have any use in a home.
Ultrasonic Devices: Do not buy ultrasonic devices to repel flies and other pests; they don't work because the pests cannot detect ultrasound. There is no scientific basis for the claims made for such devices against insects.
Freezing: Many insects, particularly clothes moths and stored food pests, can be killed by sealing the goods in plastic bags and placing them in the freezer for three to five days. This kills all stages of the pests without harming food or fabric. While the food or clothing is in the freezer, thoroughly vacuum and clean the cupboards to prevent re-infestation when the items are returned.
Pesticides: The following pesticides are the least toxic products available commercially for
use against household pests. To use any pesticide, always follow directions on
the label. Wear a dusk mask while applying dust formulations and rubber gloves
to apply liquids. Store all pesticides out of reach of children and pets. The
following are active ingredients, some of which are available under a variety of
product names.
- Boric Acid is a fine powder with low toxicity to humans, yet it is a stomach poison to insects. It is formulated into domestic pest control products for ants and other household pests. Apply it where children and pets cannot reach it because it could be harmful if they eat enough of it.
- Diatomaceous Earth (often listed as silicon dioxide) is a non-toxic, white powder made from ground up shells of diatoms mined from ancient marine deposits. It kills insects by causing them to dehydrate. Use plain diatomaceous earth or products formulated with pyrethrins.
- Pyrethrins are fast-acting, short-lived compounds extracted from pyrethrum daisies. They have a quick knock-down effect on many insects and are ideal for driving insects out of crack and crevices.
- Silica Gel is a non-toxic dust made from the silica in sand. It works like diatomaceous earth, causing insects to dehydrate. Products are usually formulated with pyrethrins; they are not yet widely available.
Common Household Invaders
Ants entering houses on foraging expeditions are a common nuisance*. [Footnote: *(For large
ants that may be living in the house, refer to another brochure in this series
entitled "Carpenter Ants").] Some look for sweet foods, others go for pet food, crumbs and garbage. To avoid attracting ants, make sure garbage is tightly covered, clean up food spills promptly, wipe jam or syrup bottles clean on the outside and keep any attractive food in tightly sealed containers or in the refrigerator. The best control is to follow the ants, find their entry point, then seal the crevices or cracks (often around a window). Wipe up invading ants with soapy water to erase the odor trails they leave for other ants to follow. Persistent ants can also be killed by dusting boric acid, diatomaceous earth or silica gel with pyrethrins into the cracks where they are entering the house. Commercial ant baits containing boric acid can be used to eliminate the nests of foraging ants it they are a severe nuisance. Ants, however, are important, beneficial contributors to the ecosystem so it is not a good idea to kill their nests unless absolutely necessary. Place the bait containers where ants will find them, but out of the reach of children and pets. If the ants are living in a potted plant or in the soil near the house, they can often be driven out by flooding the nest with water, repeatedly if necessary.
Carpet beetles are destructive pests of natural fibres, fur, leather, and other animal products. They used to be common pests of wool carpets before synthetic fibres became popular, but they still damage furniture, clothing, shoes, natural fibre rugs and other goods. The brown, bristly larvae do the damage, therefore, if you find any larvae wandering in the house it is a good idea to search cupboards, closets and under rugs for the source of the infestation. Follow treatments given for clothes moths, including washing, dry cleaning or freezing clothing, thoroughly brushing and vacuuming around and under furniture and rugs.
Earwigs are a nuisance when they get into the house, but outdoors they are important predator
of aphids and other pests in orchards. They also chew on flower petals, corn
silks and enlarge puncture wounds in ripe fruit. Prevent them from entering the
house with good screens and sealed cracks; after cutting flowers or picking
vegetables, give the produce a good shake outdoors to dislodge earwigs before
you bring it indoors. If you really must kill earwigs, trap them in tightly
rolled up lengths of corrugated cardboard or newspaper or in half-meter lengths
of old garden hose. Lay the traps along the baseboards or inside the house
foundation where the earwigs seem to be entering. The traps are attractive
because earwigs like to crawl into tight crevices. You can kill the earwigs
hiding in the traps by knocking them into a bucket of soapy water or by
disposing of the entire trap with the earwigs.
Flour moths and flour beetles are common pests in stored products. They can infest flour, pasta, grains, dried beans, nuts, dried fruit, candy,
spices and other food; they also infest dry pet food, bird seed, dried flowers
and even tobacco. Flour moth larvae leave a trail of silk thread behind so food
infested with them contains clumps of food spun together with webbing. Flour
beetles show up as small, reddish brown or nearly black specks. Bulk food stores
as well as supermarkets are occasionally a source of such pests when they bring
in products that became infested in warehouses. The older food is, the more
likely it is to develop an infestation, so buy small amounts and use them up
quickly or store surplus in the freezer until needed. A wise precaution,
especially when you buy from open bins, is to seal the food in a plastic bag as
soon as you bring it home and freeze it 3-5 days before putting it in a
cupboard. Insects can get into cardboard or paper packages, therefore dry and
bulk food should be stored in glass or heavy plastic containers with tight lids.
If you find an infestation, dispose of the contaminated food and inspect the
other food in the cupboard. Even it it looks clean, it is still a good idea to
freeze treat it before replacing it on the shelf. Vacuum or wash out the
cupboards to clean up spilled food and remove other stages of the pests (moth
larvae leave the food to spin their cocoons nearby). A light dusting of
diatomaceous earth or silica gel throughout the cupboards will help prevent
further problems.
Larder beetles particularly infest pet food and other high protein foods, such as cheese and meat. Keep such foods in the refrigerator or tightly covered containers and take steps as for flour moths.
Fruit flies are tiny, harmless flies with reddish eyes. They are usually a nuisance in the summer,
which is when their eggs are often brought into the house on fresh fruit. In
warm weather it takes only a few days for the immature stages to develop into
adults and, since every female can lay hundreds of eggs, an infestation can
develop very quickly in a small amount of fermenting fruit or other food.
Removing their breeding sites immediately remedies the problem. Keep fruit in
the refrigerator and take any kitchen garbage containing food scraps out of the
house several times a week. If you compost kitchen waste, it is a good idea to
bury it in the compost pile every day or two in warm weather.
House flies breed in any wet, decaying organic material so make sure that kitchen garbage is
tightly covered and that pet food is used up daily. Flies are not usually a
severe problem in areas with dry summers, but can be numerous in wet regions and
around livestock stables. Use screens to prevent flies from entering houses; fly
swatters and flypaper are good, non-toxic controls for flies that do get inside.
Commercial fly traps that employ attractant baits can be used to catch large
numbers of flies where there are high populations, but it is still a good
practice to find out where the flies are breeding and correct the problem, if
possible.
Silverfish and firebrats are similar, elongate, scaly insects. They are occasional pests in houses and apartments,
where they particularly like the damp, warm conditions around kitchen and
bathroom plumbing. To find out whether there is an infestation, place traps made
of file cards painted with a thin coat of honey, around plumbing fixtures and
baseboards (but not where they will be stepped on). Another simple trap is an
upright, small, very clean glass jar with the outside covered with masking tape.
The tape allows the insects enough traction to climb the sides, but when they
fall in, the slippery glass interior prevents them from escaping. No bait is
necessary. The best long-term control it to remedy the damp conditions. For
persistent infestations, dust diatomaceous earth, silica gel or boric acid into
cracks and crevices; apply dust into any gaps in the walls around plumbing
fixtures, then caulk around the pipes. In an apartment building, a thorough
control program might require cooperation of all of the tenants, but there is no
need to use more toxic pesticides.
Sowbugs and pillbugs are grey, segmented crustaceans, common where conditions are damp enough for them to survive. They die quickly from dehydration, therefore the best control is to dry out their hiding places. Make sure that damp leaves or plant material are cleared away from foundations, that cracks in basement walls are sealed and that weatherstripping around basement doors and windows is in good condition. In earthern crawlspaces and old foundations where dampness is a chronic problem, sowbugs may always be present. Other than being a nuisance, they cause no damage to the house or the goods inside. Pillbugs (the ones that roll themselves into a ball) do, however, eat small seedlings in gardens and flowerbeds. The best remedy for this is to let the soil dry out well on the surface between waterings. If pillbugs are really numerous, apply a dusting of diatomaceous earth to the seedbed.
Spiders are common predators of insects that often spin their webs in houses. Truly poisonous spiders are extremely rare, so it is unfortunate that they inspire such loathing. Prevent them from entering with good weatherstripping and screens; once they are in, vacuuming up the webs and their makers is an effective control. You might be wise to leave any spiders living in the basement or crawlspace to carry on capturing earwigs and other insects before they get upstairs.
Clothes moth caterpillars chew holes in wool, silk, cotton and even synthetic materials if they are not clean. The small greyish, brown moths flutter around the clothes cupboard or rest in the corners with wings folded. If you suspect an infestation, the best course of action is to wash, dry clean, or freeze (as above) clothing, bedding, hangings, craft yarns, etc. that might be affected. For large pieces, such as carpets, regular brushing and beating, especially in the sun, will kill the moth larvae. The larvae are so fragile that they cannot survive in clothing worn regularly, therefore it is mostly goods in storage that are damaged. There is rarely any need to use pesticides to treat these moths, but do not rely on cedar or herbal repellants to protect goods as these cannot be counted on to give adequate control of clothes moths.
For how to control other house and yard pests see additional brochures in the Safe and Sensible Pest Control series.
1994
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