Rodent Control

A Practical GuideA Practical Guide

A Practical Guide

to Rodent Controlto Rodent Control

to Rodent Control

A Practical GuideA Practical Guide

A Practical Guide

to Rodent Controlto Rodent Control

to Rodent Control

An effective rodent control program must employ methods that are relatively easy, inexpensive, and effective

under most conditions. The successful elimination of a rodent infestation in or around a dwelling usually

depends on three separate procedures: sanitation, rodent proofing, and the eventual elimination of the rats or

mice. Although sanitation of the infested area and the rodent proofing of all structures can be time consuming,

they are extremely important aspects of an effective rodent control program. Conditions that foster an

infestation of rodents must be identified and eliminated before control can be successful.

Sanitation

conducted for the control of rodents involves both the eradication of any food source for the rodents

as well as the elimination of all harborage areas. One of the most prominent food sources for rodents is

garbage. The routine storage of all garbage and rubbish in rodent-proof containers is a vital aspect of any

rodent control program. A sufficient number of receptacles must be provided to hold all garbage and rubbish

that normally accumulates between collection days. The receptacles should be rust resistant, water tight, and

have tight-fitting lids. The interior of receptacles can be kept free of organic buildup by placing all garbage in

plastic bags and tightly sealing them before placing them in the rubbish receptacles. This practice also

effectively reduces fly breeding and odors.

Other food sources in and around the home include fruits and nuts that have

not been harvested or that have fallen from trees, garden vegetables and

berries left to rot on plants, bird seed that falls from feeders and accumulates

on the ground, snails, and dog droppings not properly disposed of in the

trash.

A frequent source of food for rodents is pet food that is not completely

consumed or left out overnight. Outdoor pets should be fed only what they

can readily consume at each feeding. Food dishes should be placed away

from vegetation in clear areas that can be kept clean. Pet food and wild bird

seed stored outdoors or in garages should be kept in metal containers with

tight-fitting lids.

Elimination of harborage where rodents hide or nest is a critical step in any

successful rodent control program. Abandoned vehicles and other cast off items such as old furniture or unused

appliances and equipment should be removed from the property.

Tall grass, mature brush, ivy and other dense ground plants, and untrimmed shrubbery provide excellent

harborage for rodents. Residents should sufficiently thin ground plants, trim shrubbery to allow at least 12

inches of open area beneath plants, and remove dead fronds from the trunks of palm trees. Trees in contact

with structures should have limbs trimmed a minimum of 6 feet from roofs, attic vents, eaves, and utility wires.

Trash receptacles should be

rust resistant, water tight, and

have tight-gitting lids.

The Norway rat, roof rat, and house mouse often live in close association with humans and can be

serious pests under certain conditions. They can carry and transmit organisms that can cause disease,

damage or destroy buildings and electronic equipment by their gnawing behavior, and contaminate

surfaces with their waste products.

The dead space between double fencing at property lines not only provides excellent harborage for rodents but

makes maintenance of fences difficult. This practice is unadvisable and should be corrected. Broken and fallen

board fences and crumbling brick walls provide harborage and should be repaired. Fire wood and stored

salvageable articles must be elevated a minimum of 18 inches above ground and stored 12 inches from walls

and fences. Garages should be cleaned out and stored items organized and elevated.

Rodent proofing a building consists of changing structural details to deny rodents access to the interior of the

building. Openings as small as 1/4 inch can admit mice, and a gap of 1/2 inch will permit young rats to enter a

structure. Windows should be in good repair, and doors should fit snugly in

frames or be fitted with sweeps or channels to eliminate openings at

thresholds. Garage doors should also fit properly within the frame and be

fitted with a channel if the base does not fit tightly with the floor.

Foundation and attic vents must be screened with heavy mesh or 16 to 20

gauge galvanized hardware cloth, preferably with a sheet metal frame. Any

access to crawl spaces beneath structures should be properly screened or

securely covered, permitting no gaps at the edges of the frame. Openings

around pipes or conduits must be covered with sheet metal patches or filled

with concrete or brick and mortar. Gaps at intersecting roof eaves or where

the chimney intersects the roof must be repaired or screened.

Evidence of rodents can be determined by one or a combination of specific

signs. When in the home, rodents can frequently be heard gnawing on wood

or climbing between the walls. They also emit squeaks and can sometimes be heard fighting over food or

mates. Droppings can be found along frequently traveled paths, near nesting sites, among food caches, or other

areas the rodents frequent. The odor of

wet or dry urine may also be present in

these areas. Footprints or tail marks

may be observed on dusty surfaces.

Dogs or cats may excitedly probe an

area of floor or wall, or any other

harborage site, especially if the rodents

have recently invaded the area. Rub

marks may be found on vertical surfaces

such as walls or entrance and exit sites,

where dirt and oil from rodent fur leave

darkened patches or streaks.

Rodents gnaw on a variety of materials

such as aluminum, mortar, plastic, and

lead. Tooth marks or chips of gnawed

material may be found around

baseboards, doors and windows, cabinets, furniture, or stored materials.

Rodents also gnaw at cracks or small openings in an attempt to enlarge

openings and gain access to structures. Nests composed of furniture stuffing, shredded paper or other soft

materials, and food caches of nuts, pet food, snail shells or empty fruit rinds will sometimes be discovered when

residents clean out garages, tool sheds, attics, closets, or other storage areas. Roof rat nests may sometimes

be found when dense vegetation is trimmed or thinned.

When rats occur within the home, use snap traps or glue boards; avoid using poison baits. If rats succumb to

poison baits and die in inaccessible areas, the odor of decay can last for several days. When trapping rats with

snap traps, the best success is obtained by continuing to place baited but unset traps out for several nights until

the rats have become accustomed to the presence of the traps. When the bait has been readily accepted, rebait

and set the traps. Use a bait that can be secured to the trigger. Fasten bait such as peanut butter on cotton or

Items stored outdoors must be

a miniumum of 18 inches off the

ground.

Doors should fit snugly in

frames or be fitted with sweeps

or channels to eliminate

openings.

Openings around pipes must be

covered with sheet metal or

filled with concrete or mortar.

raw bacon to the trigger with light string or fine wire so that when attempting

to remove the bait, the rodent will be sure to spring the trap. Mice will readily

investigate snap traps and no pre-baiting activities are necessary.

Glue boards should be secured to a stationary object with a nail or wire.

They can be placed in well established runways, but not in corners. Placing

bits of apple, nuts, or dry dog food in the center can be effective.

Snap traps should be placed in areas where rodent activity has been noted,

such as across obvious runways, or where runs are confirmed by the

presence of droppings or rub marks. When trapping for mice, the trap

should extend from the wall at right angles, with the trigger end nearly

touching the wall. When trapping for rats, set the traps parallel to the wall,

back to back, with the triggers situated to intercept rats coming from either

direction. Boxes or boards can be positioned in such a manner as to guide the rodent into the trap. When

trapping for mice, the best success is often obtained the first night of trapping. For this reason, it is important to

set out more traps than the estimated number of rodents. Always continue with control efforts until no new signs

of rodents are visible.

Outdoors, rodent runs may be found next to walls, along fences,

under bushes or buildings, or anywhere their feet make beaten

paths on the ground. Roof rat runs along beams in garages or

other buildings are often encrusted with urine and fecal material.

Expanded trigger traps provide a larger contact area and are often

very successful in highly traveled areas . When secured across

such runs, position the trigger end over the visible run so the rat

will pass directly over the trigger. Do not use bait when placing

expanded trigger traps over visible rodent runs.

When using poison baits, read and follow all label directions.

Place poison in properly secured bait stations out of the reach of

children, pets, and non-target animals. Never place poison bait in

any type of food container and keep one empty bait package for

emergency treatment information.

Do not expect rodents to go out of their way to locate the poison

bait. Bait stations placed in protected areas or under cover

adjacent to travel ways or suspected harborage sites are more successful than those located in open areas.

The number of bait stations placed will depend on the suspected number of rodents within the area. Monitor bait

stations regularly. If bait disappears rapidly, place additional stations. Multiple dose rodenticides must be

consumed over a number of days to produce death, and the interval between feedings should not exceed 2

days. It is important to the success of the control program that stations provide bait continuously during the

duration of the program and until no new signs of rodents are observed.

Always use safety precautions when cleaning rodent infested areas and discarding dead rodents or traps. Wear

rubber, latex, vinyl or nitrile gloves. Disinfect trapped rodents and contaminated materials and surfaces by

thoroughly wetting them down with disinfectant. Remove disinfected materials with dampened paper towels or

cloth, place in a plastic bag, tightly seal it, place in a second plastic bag, seal it, and dispose of it in the trash.

Disinfect the gloves prior to removing them, and dispose of in the trash. Wash hands thoroughly with soap and

water.

A Pest Bulletin distributed by:

Los Angeles County - Department of Health Services

Vector Management Program

5050 Commerce Drive

Baldwin Park, California 91706

(626) 430-5450

Place traps in areas where

rodent activity has been noted.

When expanded trigger traps are secured

across roof rat runs, position the trigger

end over the visible run so the rat will pass

directly over the trigger.

1. Remove all dead palm fronds.

2. Trim tree limbs and high plants six feet away from

roof, attic vents, eaves, and utility lines. Thin ivy

and other thick vegetation, and leave clearance

beneath bushes to prevent harborage for rodents.

3. Avoid double fencing. It provides space for

rodent harborage.

4. Remove dog droppings daily and feed pets away

from vegetation and harborage areas. Do not

leave pet food out over night.

5. Remove old vehicles and non-salvageable items

from property.

6. Elevate stored items at least 18 inches above

ground and 12 inches from walls and fences.

7. Use 1/4 inch galvanized hardware cloth for vent

and crawl space screens. Frames should fit

properly with no gaps at the edges.

8. Seal gaps around pipes entering walls with 1/4

inch hardware cloth, sheet metal, concrete, or

mortar.

9. Screen openings at intersecting roof eaves and

where chimney intersects roof.

10. Repair all plumbing leaks.

11. Install door sweeps or weather stripping on all

exterior doors. Close all openings greater than

1/4 inch to exclude rodents.

12. Bait stations can be made out of 1/2 gallon or 1

gallon plastic containers, such as bleach bottles,

and placed in trees for roof rats. Cut two holes in

container on opposite sides, about 1 1/2 to 2

inches in diameter. Secure in place with wire to

avoid spillage. Place bait in container and replen-

ish for 10 to 14 days or until no new signs of rats

are observed. The label from the pesticide pack-

age should be attached to the plastic container.

13. Dispose of trash properly.

14. Remove and properly discard ripe and fallen fruits

and vegetables.

15. Clean and organize garage and storage buildings.

Make certain doors close properly.