Subterranean 

Termites—

Their Prevention and Control 

in Buildings

United States 

Department 

of Agriculture

Forest Service

Home and Garden 

Bulletin 64

Revised

October 2006
Subterranean 

Termites—

Their Prevention and Control 

in Buildings

United States 

Department 

of Agriculture

Forest Service

Home and Garden 

Bulletin 64

Revised

October 2006

Chris Peterson 

Terence L. Wagner 

Joseph E. Mulrooney 

Thomas G. Shelton

USDA Forest Service 

Wood Products Insect Research Unit 

201 Lincoln Green 

Starkville, MS 39759
Abstract

Subterranean termites are the most important 

insect pest of wood in the United States. Living in 

large underground colonies, termites may attack 

any wood in contact with the soil and may even 

construct protective shelter tubes over nonwood 

materials to attack wood above ground. Most 

damage in the United States is caused by termites 

in the genus Reticulitermes, but an invasive termite, 

the Formosan subterranean termite (Coptotermes), 

causes extensive damage in some areas. Termites 

occur in all 50 States except Alaska but are most 

common in the Southern States. Termites prefer 

warm, moist environments, and home builders 

and homeowners often unwittingly increase the 

likelihood of termite infestations in homes and 

other structures by creating such environments. 

Termite prevention begins with good building 

practices, which vary depending on the type of 

structure and how the structure is to be landscaped 

and decorated. The use of soil-applied insecticides 

during construction is the most widely employed 

method of preventing termites and has a long 

history of success. Use of pressure-treated lumber 

is another successful practice, but termites may 

tunnel over treated wood to reach untreated 

wood elsewhere. Control of termites in existing 

structures involves periodic inspections for termite 

activity, remedial insecticide treatments, or use of 

insecticidal bait technology. 

KEY WORDS: insecticidal bait, insecticide, pest 

control, Reticulitermes, structural protection, 

subterranean termite, wood product protection
Contents

Introduction..................................................................................................................................... 1

Termites—Biological Considerations............................................................................................. 3

Termite Ecology ....................................................................................................................... 3

Distribution of Subterranean Termites ..................................................................................... 3

Biological and Physical Characteristics of the Subterranean Termite Colony ......................... 4

Materials Damaged by Subterranean Termites......................................................................... 6

Conditions Favoring Subterranean Termite Infestation............................................................ 7

Detection of Damage Caused by Subterranean Termites......................................................... 7

Planning and Construction To Prevent Attack by Subterranean Termites....................................... 9

Good Building Practices........................................................................................................... 9

 The building site ................................................................................................................ 9

 Crawlspace (wall and pier or “conventional”) foundations............................................. 10

 Concrete slab-on-ground foundations.............................................................................. 12

 Basement foundations...................................................................................................... 13

 Physical barriers............................................................................................................... 15

 Exterior woodwork........................................................................................................... 15

 Raised porches and terraces of concrete or masonry....................................................... 17

Direct Control Methods.......................................................................................................... 17

 Chemical soil treatment before construction ................................................................... 18

 Considerations when treating new construction .............................................................. 22

 Naturally resistant woods................................................................................................. 23

 Chemically treated woods................................................................................................ 23

Control of Subterranean Termites in Existing Buildings.............................................................. 24

Inspection ............................................................................................................................... 24

Sanitation................................................................................................................................ 24

Chemical Control ................................................................................................................... 25

Termiticidal Baits................................................................................................................... 26

Other Insects That Damage Wood in Buildings............................................................................ 29

Risk Factors for Termite Problems—A Checklist......................................................................... 30

Acknowledgments......................................................................................................................... 31

Pesticide Precautionary Statement................................................................................................ 32
1

Introduction

Subterranean termites are the most destructive and 

economically important pests of wood and other 

cellulose products. They attack wood throughout 

most of the United States, with the exception of 

Alaska. They are most common, and hence most 

destructive, in the warmer regions (fig. 1).

The economic cost of termite damage to wood used 

in and around buildings is great. It is difficult to 

establish the exact amount of damage caused by termites, but estimates of yearly damage of $1 billion 

are common, and some are as high as $7 billion. 

These numbers may or may not include the cost of 

treatments (both preventive and curative), repairs 

to damaged buildings, loss of property value, and 

damage not immediately attributed to termites (such 

as wind damage to weakened structures). In any 

case, much damage certainly goes unreported. Termites also do considerable damage to wood used as 

utility poles, fence posts, and similar products. 

The rising costs of termite control are attributed to 

several factors. Slab-on-ground construction and 

concrete or masonry terraces adjacent to foundation 

walls favor termite attack and result in increased 

damage to buildings. Slab-on-ground construction 

is also the most costly to treat after construction. 

Repairs, remodeling, and landscape changes (if 

Figure 1. — Relative hazard of subterranean termite infestations in the United States.
2

made without regard to termite prevention and 

control) often lead to termite problems and impair 

the effectiveness of any prior chemical treatment. 

The best time to prevent future termite problems 

is during construction (see the discussion starting 

on page 9 for more details). Preventive efforts in 

the planning stage may save the homeowner much 

anxiety and expense. Buildings should be designed 

and built to minimize moisture uptake and retention 

by wood. Additions or repairs to buildings or 

changes in landscape also should be designed to 

minimize the chances of termite infestation. Proper 

protection from termites requires a cooperative 

effort by architects, builders, pest management 

professionals, and property owners. 

A combination of nonchemical and chemical 

techniques is recommended for termite prevention 

and control. Sanitation measures and chemical 

treatments are the most effective. Proper sanitation 

involves removing all stumps and wooden debris 

from the building site before and after construction 

(including form boards and scraps). Burning of 

such materials is not sufficient, because burning 

does not destroy the underground portions of 

stumps or buried materials. Chemical protection 

involves treating the soil with an approved chemical 

before, during, or after construction. Chemical 

prevention provides a barrier against termite 

movement into wooden housing parts. Termite 

baits have become available in recent years for use 

in place of or in conjunction with chemical soil 

treatments.

Only a small percentage of the more than 105 

million single-family homes in the United States 

have been treated to control termites. This number 

does not include rental, commercial, or institutional 

structures. Some States require termite treatments, 

but nationwide few structures are treated during 

construction, although this is the most effective 

and economical time to prevent future termite 

infestations. It is more difficult and costly to 

apply effective control measures after a building 

has become infested with termites, but a control 

program usually can be implemented successfully. 

An infested building should be examined to 

determine which type of termite is causing the 

damage, the extent of the infestation, and the 

measures needed to prevent further damage. Some 

structures require simple physical changes (such 

as minimizing wood in contact with the ground), 

repairs, or chemical treatments that can be made 

by the owner. Others need major changes or 

complicated chemical treatments that require the 

services of a professional who has knowledge of 

termite habits and is experienced in pest control. 

This bulletin provides basic information to the 

homeowner and pest management professional. 

It suggests methods for preventing subterranean 

termite attack in new and existing construction. 

You may want to check these termite prevention 

measures with a professional before building or 

buying a new home or before remodeling. For the 

professional, this publication may be consulted 

to better understand the use of termite control 

products. If using chemical control measures, 

always read and follow label directions. This 

publication also tells where to look for termites in 

existing buildings, how to recognize their damage, 

and how to control them by both structural and 

chemical means. 
3

Termites—Biological Considerations

Proper termite identification and knowledge of the 

species’ biology are essential elements in termite 

control. This information provides the groundwork 

for control methods based on the habits and 

behavior of termites. 

Termite Ecology

In their natural habitats, termites are considered 

beneficial insects because they break down dead 

or dying plant materials and thus are an important 

part of the nutrient cycle. When termites feed on 

wooden structures, however, they become pests. 

In general terms, three types of termites occur in 

the United States: (1) drywood, (2) dampwood, 

and (3) subterranean termites. Drywood termites 

build their nests in sound, dry wood above ground. 

Dampwood species locate their nests in moist, 

decaying wood but can extend tunnels into drier 

parts of the wood. Subterranean termites typically 

dwell in the soil and work through it to reach 

wood above ground. In the United States, the vast 

majority of loss is caused by subterranean species.

The soil provides several advantages that make it 

suitable as the dwelling for subterranean termites. It 

serves as a source of moisture that protects termites 

against drying out, shields termites from predators, 

and is used as a building material for shelter tubes 

above ground. Termites can excavate passageways 

through the soil to reach food sources. If moisture 

is available from another source, subterranean 

termites may not require connection to the soil. 

Isolated aboveground infestations can occur in 

homes where subterranean termites have access to 

water from condensation, leaking roofs, pipes, or 

other sources. 

Distribution of Subterranean Termites

In all areas of the United States, subterranean 

termites are the most widespread and the most 

damaging of the three types. They are found in 

every State except Alaska (fig. 1). Drywood termites 

cause significant damage in localized areas, but are 

limited in distribution to the Atlantic coastal States 

south of Virginia, the entire State of Florida, the 

Gulf Coast, along the Mexican border, and along 

the Pacific Coast to just north of San Francisco. 

Dampwood termites are of only minor importance 

as structural pests and are limited to the Pacific 

Coast, the desert Southwest, and southern Florida. 

Hawaii experiences problems with all three types of 

termite. This publication will deal exclusively with 

subterranean termites. 

Most of the termite damage in the United States 

is caused by native termite species. Infestations in 

buildings, especially in the Northern States, have 

become more common with the general adoption 

of central heating units; heated basements also 

increase termite activity around structures. The 

construction of suburban homes in forested areas 

also has increased the termite problem. Changes 

in building practices and the use of certain 

construction materials increase the likelihood 

of termite infestations. Because of this, termites 

have become a problem in areas where they were 

formerly of little economic importance.

The Formosan subterranean termite, an introduced 

species, was detected in Hawaii around 1850 and 

has since become a pest of considerable importance 

on the major islands. This termite was first reported 

in the continental United States in several port cities 

along the Gulf Coast in the 1960s, but it is not yet 
4

generally distributed. It was found in Florida in 

1980, and since then it has been found in isolated 

parts of Alabama, Mississippi, Texas, Tennessee, 

Georgia, North Carolina, and South Carolina. It 

is of great importance in localized areas, such 

as New Orleans. These termites are larger, feed 

more quickly, and are more aggressive than native 

species, and they also occur in larger colonies. 

In addition, they are less dependent upon ground 

contact than the native subterranean termites and 

often can nest in walls. Currently there are no data 

suggesting long-range movement of this species on 

its own on the mainland. Its movement has resulted 

largely from human transportation of wood products 

(especially railroad ties for landscaping). This is 

an important fact to consider when transporting 

wood materials from areas where the Formosan 

subterranean termite is known to occur. 

Biological and Physical 

Characteristics of the Subterranean 

Termite Colony

Termites are social insects that live in highly 

organized colonies. Each colony is composed of 

“castes” of individuals that have different physical 

features (fig. 2) or behavioral roles, or both. Three 

Figure 2. — Typical subterranean termite life cycle.
5

Figure 3. — Soldier (top, with enlarged head and 

mandibles) and worker termites.

Figure 4. — Winged adult termite.

types of individuals make up the termite caste 

system: workers, soldiers, and reproductives (which 

may or may not be winged). Other intermediate 

forms are also present, but are rarely observed by 

the homeowner or pest management professional. 

One can identify termite species by noting physical 

characteristics of the soldiers and reproductives. 

Physical characteristics distinguish the different 

termite castes. Worker termites (fig. 3) are wingless, 

soft bodied, and white or yellow-white. They are 

found in the greatest numbers in a subterranean 

termite colony and are the ones most frequently 

seen when infested wood is examined. The duties 

of these reproductively undeveloped individuals are 

to care for the eggs and young, feed and clean other 

termites, forage for food, and construct and repair 

shelter tubes and other workings. This is the caste 

that actually eats the wood. Soldiers (fig. 3) have 

larger, brownish heads and longer mouthparts than 

workers. They guard the colony and defend against 

predators. Reproductives (fig. 4), or sexual adults, 

have black or yellow-brown bodies. They have two 

pairs of long, whitish, translucent wings of equal 

size at the time when they disperse from the colony, 

but they shed their wings soon after flight. With 

increased age, the body of a functioning female 

reproductive may become greatly expanded with 

developing eggs and will attain a size several times 

that of workers. 

Ants are often mistaken for termites, but readily 

visible characteristics differentiate the two very 

different insects. Ants, when winged, have two pairs 

of transparent wings of unequal size; termites have 

two pairs of equal-sized wings. Also, the region 

of the body behind the wings is “pinched” in ants 

but broader in termites. The antennae of ants are 

elbowed, while those of termites are straight and 

beadlike. These and other distinguishing features 

are pictured in figure 5. Additionally, ants generally 

have harder bodies than termites. Termite workers 

are almost always soft bodied and white to yellow 

(sometimes caramel colored), but rarely red, dark 

brown or black like ants. Finally, subterranean 

termites are almost never seen foraging out in the 

open.

A subterranean termite colony is self-perpetuating. 

When the colony is composed of a large number of 

individuals, a small percentage of workers develop 

into winged reproductives that then fly in swarms to 

establish new colonies. Most winged reproductives 

perish during the flight because of predators such as 

birds, bats, lizards, or other insects. The time of day 

and year when flights occur varies with the species 

of termite and its geographic location. Flights often 

occur during the first warm days of spring after a 

rain (therefore earlier in the year in the South than 

in the North), but they can occur at any time of the 

year. In buildings with heated basements, termites 

occasionally fly during winter.
6

Figure 5. — Physical characteristics distinguish termites from ants.

Males and females in the flights are referred to as 

kings and queens, respectively. They shed their 

wings after the flight, and each pair excavates a 

cell in or near wood in the ground and mate. Most 

subterranean species in the United States lay fewer 

than 100 eggs during the first year, but egg laying 

increases with time.

Depending on species, a colony more than 5 or 

6 years old may contain from several thousand 

to over a million termites and produce winged 

reproductives each year. In some situations, a 

few workers may develop into reproductives and 

supplement the egg laying of the original queen. 

Materials Damaged by Subterranean 

Termites

The principal food of subterranean termites is 

cellulose obtained from wood and other plant 

tissues. Termites feed on the wooden portions of 

buildings, utility poles, fence posts, or other wood 

products. They can also damage paper, fiberboard, 
7

and various types of fabrics derived from cotton 

and other plants. They occasionally are found in 

living plants and sometimes in puffball mushrooms. 

As termites search for food, they can damage many 

noncellulose materials, including plastics, rubber, 

and even thin metal, although these do not serve as 

food sources. 

Conditions Favoring Subterranean 

Termite Infestation

Understanding the biological requirements and 

conditions that favor termite activities better 

prepares one to inspect buildings and identify 

potential problem areas. An important consideration 

is the termite’s dependency on moisture. Their 

high moisture requirements increase the likelihood 

that they will maintain contact with the soil or 

locate near areas where water collects (such as air 

conditioning condensers, drains, condensation from 

pipes, etc.), or both. 

Subterranean termites become more abundant in 

moist, warm soil containing a large supply of food. 

Such conditions often are found beneath buildings 

where there is inadequate water drainage, or poor 

ventilation, or where scraps of lumber, form boards, 

grade stakes, stumps, or roots are left in the soil. 

Once termites locate such an area, they can move 

into buildings in a variety of ways. Termites invade 

most buildings through wood close to or in contact 

with the soil, particularly at porches, steps, terraces, 

fences, or planters. Termites can easily enter 

small cracks or voids in foundations (including 

the center of cinder blocks) and concrete floors to 

reach wood that does not touch the soil. As with all 

insects, termite activity and development depend 

on temperature. When soil is kept warm throughout 

the year, as it is when basements are heated, 

termite activity is increased and prolonged. Such a 

“thermal shadow” exists in most structure types and 

may be increased by heating units, steam pipes, or 

electrical conduits near the soil.

Termites may eliminate their contact with the soil 

when an aboveground moisture source is available. 

Damp wood near sinks, toilets, and leaking pipes or 

wood kept moist by runoff water, as from the roof 

or gutters, is a prime location for termites.

Detection of Damage Caused by 

Subterranean Termites

Early detection of termite infestations and subsequent control measures should enable homeowners 

to protect their dwellings. A relatively simple, but 

careful, inspection of one’s home may reveal previously undetected signs of termite activity. 

Termite damage to wood often is not noticeable 

on the surface. This is because workers avoid 

exposure to air by constructing galleries within 

the materials they attack. Severely damaged wood 

may have a hollow sound when tapped. Prodding 

with a screwdriver is a simple way to determine 

the soundness of a suspected piece of wood. The 

exterior surface must be stripped away in order to 

see the extent of damage. Extensive tunnels that run 

along the grain are signs that subterranean termites 

have attacked the wood (fig. 6). These galleries are 

often covered with yellow-brown or gray specks 

of excrement and soil. Occasionally, termites 

completely honeycomb wooden timbers, leaving 

little more than a wooden shell. Subterranean 

termites do not reduce the wood to a powdery mass 

Figure 6. — Wood damaged by subterranean termites.
8

or push wood particles to the outside, as do many 

other woodboring insects (such as beetles and 

carpenter ants).

In exposed areas, termites must protect themselves 

from the drying effects of air. Thus, earthen shelter 

tubes constructed over the surface of foundation 

walls are typical signs of termite infestation (fig. 7). 

These tubes are usually about 1/4 to 1/2 inch wide, 

and termites use them as passageways between the 

wood and the soil. To determine if an infestation 

is active, break a section of the tube and watch for 

termites. If you do not see any termites, then check 

back in several days to see if the termites repair the 

damaged tubes or build new ones. 

Most subterranean termite species found in the 

United States do not construct a clearly defined 

nest. The Formosan subterranean termite, however, 

often builds “carton” nests within walls. The 

carton nest is a honeycombed mass composed 

of chewed wood, saliva, and feces that retains 

water and protects the termites from predators. 

Although occupied carton nests are relatively moist 

and pliable, abandoned nests dry and harden to a 

concrete-like consistency. 

Large numbers of winged termites swarming from 

the soil or wood are often the most obvious sign 

of a nearby termite colony. Although flights may 

not be observed, discarded wings on the floor 

beneath doors or at windowsills suggest that winged 

termites have either emerged within a building 

and have been unable to escape, or have emerged 

nearby. Winged reproductives are produced by 

well-established colonies, often containing at 

least several thousand members, and colonies of 

hundreds of thousands are common.

Figure 7. — Termite shelter tubes.
9

Planning and Construction To Prevent Attack by Subterranean 

Termites

The best and least expensive time to protect a 

building against subterranean termites is during 

planning and construction. 

Improper design and construction of buildings, 

resulting from either lack of knowledge or 

indifference to the termite problem, are favorable 

to infestation. It is therefore important to use good 

building practices and chemical soil treatments 

during construction.

Good Building Practices

The building site—All roots, stumps, and 

other wood debris should be removed from the 

building site before construction starts. Burying 

such material will only increase the probability 

of infestation, and burning will not destroy 

underground portions. Wooden spreader sticks and 

grade stakes should be removed before the concrete 

hardens. Form boards and scraps of lumber should 

be removed before filling or backfilling around the 

completed foundation. Wood should not be buried 

beneath porches and steps (fig. 8). No scraps of 

lumber should be left on the soil surface beneath or 

around the building after construction. 

To prevent moisture buildup in the soil beneath a 

building, the soil surface around the building should 

be sloped so that water will drain away from it. 

Gutters and downspouts attached to eaves can help 

remove water quickly. Where there is poor surface 

drainage, as on flat surfaces or around buildings 

Figure 8. — Termite colonies can develop in woody debris and gain access to the structure.
10

with basements, the use of drainage tile around 

the outside of the building foundation may prove 

helpful.

Crawlspace (wall and pier or “conventional”) 

foundations—The proper construction of 

foundations is one of the most important measures 

that can be taken to protect against termites and 

should be considered very carefully. All foundations 

should be made as impervious to termites as 

possible. Crawlspace foundations may be rated 

from most to least resistant as follows:

1. Poured concrete wall and pier foundations 

(fig. 9) that are properly reinforced to prevent 

large shrinkage or settlement cracks are the 

most resistant. Termites can use cracks as small 

as 0.03 inch (0.8 mm).

2. Hollow block or brick wall foundations are 

less resistant, depending on how they are 

capped:

Figure 9. — Poured concrete walls and piers are easily inspected for hidden termite infestations.

a. The most resistant of this type are capped 

with reinforced poured concrete at least 

4 inches (10 cm) thick (fig. 10).

b. If foundation walls are capped with solid 

concrete blocks, all joints should be 

completely filled with cement mortar.

c. If the top course is hollow blocks, all 

joints should be completely filled with 

concrete. Where hollow blocks remain open 

no protection is provided unless all voids 

are chemically treated, or the soil beneath 

the footing is treated before the footing is 

poured. Do not apply a termiticide to voids 

filled with rigid foam insulation.

3. Wooden piers or posts used for foundations 

are the least resistant and should be pressure 

treated with an approved preservative by a 

standard process. Some States require this in the 

building code. However, even pressure-treated 

piers are susceptible to termite attack because 

the treatment may not extend to the center of the 
11

pier. Cut ends of pressure-treated piers should 

not be placed in direct contact with the soil.

Ventilation beneath buildings—Ventilation 

openings in conventional foundation walls should 

be large enough and distributed to prevent dead 

air pockets from forming. Such pockets give rise to 

humid conditions conducive to termite activity and 

wood decay. Openings placed within 10 feet (3 m) 

of the corners of buildings usually give the best 

cross ventilation. The openings need not be placed 

on the front side of a building if unventilated areas 

can be avoided. The size and number of openings 

depend on soil moisture, atmospheric humidity, 

and air movement. In general, the total area of 

ventilation should be 1/150 of the ground area 

beneath the building. Shrubbery should be kept 

far enough away from the openings to permit free 

air circulation and should be far enough from the 

foundation to allow inspection of wall surfaces for 

the presence of termite tubes.

Skirting between foundation piers—Where pier 

foundations are used, it is sometimes desirable to 

close the spaces between the piers with lattice or 

wooden skirting. If this is done, the woodwork 

should be separated from the piers and soil by at 

least 2 inches (5 cm).

Water pipes and conduits—Keep all plumbing 

and electrical conduits clear of the ground in 

crawlspaces. Suspend them from girders and joists 

where possible. Do not support them with wooden 

blocks or stakes connected to the ground because 

termites will tunnel through these wood supports or 

construct tubes over them to sills, floors, and joists 

above. Chemically treat the soil around plumbing 

extending from the ground to the wood above. 

Where pipes or steel columns penetrate concrete 

slabs or foundation walls, fill the spaces around 

them with either dense cement mortar or roofinggrade coal-tar pitch after the soil around the pipe or 

column has been chemically treated.

Figure 10. — Reinforced poured concrete cap on masonry walls prevents hidden attack by termites. Clearance 

between the floor and soil should be at least 18 inches (46 cm).
12

Closed crawlspace foundations—Closed 

crawlspace foundations consist of conventional 

crawlspace foundations that use a mechanical 

heating and cooling system to control temperature 

and moisture. No ventilation to the outside 

is provided, and the walls and floor above 

are insulated to retard heat loss and moisture 

condensation. The ground, and frequently the walls, 

must be covered with a plastic vapor barrier or 

insulated. When installing insulation in a closed 

crawlspace, a strip at least 3 inches (7.5 cm) wide 

must be left exposed along the top perimeter of the 

foundation wall to allow for detection of termite 

tunnels during inspection. Special attention must 

be given to the inspection and treatment of these 

structures as accessibility of closed crawlspace 

areas and soil is severely restricted.

Concrete slab-on-ground foundations—One of 

the most susceptible types of construction, and 

one that often gives a false sense of security, is 

the concrete slab-on-ground foundation. Termites 

can gain access to the building over the edge 

of the slab, through expansion joints, through 

openings around plumbing, and through cracks in 

the slab. Infestations in buildings with this type of 

construction are very difficult to control. 

Because the slab-on-ground construction is 

extremely susceptible to termite attack and 

infestations are difficult to control, treat the soil 

with chemicals before pouring the concrete. Such 

soil treatments, properly applied, are effective and 

much less expensive and invasive than remedial 

treatments at a later date. 

Do not leave any untreated wood such as forms, 

scraps, grade stakes, or wood plugs in or beneath 

the slab. Reinforce the slab at all points where it is 

likely to crack. 

Termites can penetrate some types of slabs more 

easily than others. The monolithic slab (fig. 11) 

provides the best protection against termites. In this 

Figure 11. — Monolithic concrete slab-on-ground construction.
13

type of construction the floor and the footing are 

poured in one continuous operation, eliminating 

joints or other structural features that permit termite 

entry. 

A second type is the suspended or supported slab 

(fig. 12) that extends completely across the top of 

the foundation. Here the slab and the foundation are 

constructed as independent units. This prevents hidden termite attack because even though a vertical 

crack may develop in the wall, termites still must 

tunnel over an exposed part of the slab. The lower 

edge of the suspended slab should be open to view. 

With the monolithic and suspended slabs, the slab 

should be at least 6 inches (15 cm) above grade.

A third type is the floating slab (fig. 13). It may 

either rest on a ledge of the foundation or be 

independent of it. In both instances the slab is in 

contact with the ground. This is the most hazardous 

of the three types of slabs because the slab edges 

come in contact with the foundation walls, and 

termites may gain hidden access to the wood 

through expansion joints.

Basement foundations—In many ways, a house 

with a basement can be seen as a conventional foundation house built over a concrete slab on ground, 

with continuous walls of poured concrete, cinder 

block, or brick (sometimes stone). Many of the 

termite considerations for basement-style houses 

will be a combination of those for conventional 

and slab-on-ground construction, and the reader 

should consult those parts of this booklet. “Dirt 

basements,” where the structure is built over an 

excavated area, are regarded as crawlspace foundations. Basements do provide some unique situations, 

however, which are described below.

Basement rooms—Termite infestations in basement 

rooms are very difficult to detect and control. Such 

situations exist commonly in finished basements 

where untreated wood floors and furring strips are 

used. The best way to prevent such infestations is 

Figure 12. — Suspended concrete slab-on-ground construction.
14

to treat the soil below the basement floor and along 

the outside of the foundation, preferably before 

the foundation and basement floor are constructed. 

Pressure-treated lumber should be used for wood 

screeds, subflooring, and furring strips because of 

the danger of decay.

Partitions and posts—Install wooden basement 

partitions, posts, and stair carriages after the 

concrete floor is poured. They should never extend 

into or through the concrete. Wood posts, partitions, 

stair carriages, heating units, and other loadbearing 

points should rest on concrete floorings that extend 

at least 3 inches (8 cm) above the floor level. Use 

reinforced concrete because the concrete may crack, 

providing entrance points for termites (fig. 14).

Windows below grade—Where window frames 

or other openings near or below outside grade are 

made of wood, the foundation wall surrounding the 

wood should be made impervious to termites. The 

bottom of the window well should be at least 6 inches 

(15 cm) below the nearest wood.

Girders, sills, and joists—Wooden girders, sills, 

and joists that are in or on foundation walls in 

basements should not be placed below the outside 

grade level. Termites may find hidden access to this 

Figure 13. — Slab-on-ground construction (floating slab): (above, left) slab suspended on foundation wall; (above, 

right) slab rests entirely on ground.

Figure 14. — Posts in concrete: Certain situations increase vulnerability to termite attack.
15

wood and it may be subject to decay. Because of the 

difficulty of replacing girders, sills, and joists, it is a 

good practice to use preservative-treated lumber for 

these structural members. Termites generally will 

not eat wood treated with preservatives, but they 

will tunnel over treated wood to reach untreated 

wood.

Physical barriers—For conventional foundations, 

metal or plastic termite shields (fig. 15) have been 

used as a replacement for the concrete cap or 

other methods of sealing masonry foundations. 

If properly designed, constructed, installed, and 

maintained, shields will force termites out into the 

open, revealing any tunnels constructed around 

the edge and over the upper surface of the shield. 

Experience has shown, however, that very few 

shields are properly constructed and installed and 

that homeowners usually fail to inspect shields 

frequently enough to detect termite infestations. 

The shields make infestations easier to detect, but 

do not provide effective protection and should not 

be solely relied upon to control termites.

In recent years stainless steel mesh and plastic 

physical barriers have been introduced. Such 

materials are placed underneath the slab before 

the concrete is poured (fig. 16). If the material 

is impermeable plastic, it may be used in lieu of 

the vapor barrier, if that is in accordance with the 

manufacturer’s instructions. Areas around pipes, 

conduits, and other service penetrations of the 

slab receive an additional protective flange of the 

material to prevent termite entry (fig. 17). When 

wooden posts are in direct contact with the ground, 

such as for a deck support, the posts are wrapped 

with a sleeve of material (fig. 15). Some physical 

barriers are impregnated with insecticide to provide 

even more protection.

Exterior woodwork—Finishing work on the 

outside of buildings should be constructed with the 

prevention of termite infestations in mind. 

Clearance between wood and soil—Except when 

a basement is present, the outside finished grade 

should always be equal to or below the level of the 

soil underneath the structure (figs. 9, 10, and 18) 

Figure 15. — Physical barriers: (above, left) around a post; (above, right) as a wall cap (termite shield).
16

Figure 16. — Physical barrier placed beneath the slab over gravel fill.

Figure 17. — Protective physical barrier embedded in concrete around service penetrations.
17

so that the foundation wall is exposed and can be 

inspected. This will help prevent the collection 

of water underneath the house. Siding should not 

extend more than 2 inches (5 cm) below the top 

of the foundation walls, piers and concrete caps, 

and should be at least 6 inches (15 cm) above the 

outside grade. This will force termites out into 

the open where their tunnels can be seen before 

they reach the wood. In crawlspaces the minimum 

clearance between the ground and the bottom of 

the floor joists should be 18 inches (46 cm); such 

clearances for beams and girders should be 12 inches 

(30 cm) (fig. 18).

Wooden porches and steps—Porch supports (such 

as piers) adjacent to a building should be separated 

from the building proper by 2 inches (5 cm) to 

prevent hidden access by termites. Wooden steps 

should rest upon a concrete base or apron that 

extends at least 6 inches (15 cm) above the grade 

(fig. 19).

Door frames—Door frames and jambs should never 

extend into or through a concrete floor. 

Raised porches and terraces of concrete or 

masonry—Dirt-filled porches and terraces 

contribute to a large proportion of all termite 

infestations in buildings. Therefore, spaces beneath 

concrete porches, entrance platforms, and similar 

raised units should not be filled with soil. Such 

spaces should be left open with access doors for 

inspection. If this cannot be done, or if the spaces 

beneath such raised units must be filled, leave 6 

inches (15 cm) of clearance between soil and wood 

and thoroughly treat the soil with a registered soil 

termiticide.

Direct Control Methods

Chemical treatment of the soil around and under 

the foundation is one of the prime methods of 

preventing termite attack. This should not be 

used as a substitute for good building practices. 

Figure 18. — For masonry superstructures, provide adequate clearance between wood and soil both outside and inside 

the building.
18

Chemically treated and naturally resistant woods 

can reduce the susceptibility of wooden structures 

to termite attack. Baits are not currently used 

during construction for termite control, but some 

States do allow them to be used in lieu of chemical 

treatment even though installed after construction is 

completed.

Chemical soil treatment before construction—

Insecticide-treated soil serves as one of the most 

important means of isolating a building from 

termites. Soil treatment is most effective when done 

before and during construction of the foundation. It 

is particularly important when using concrete slabon-ground construction. 

The Environmental Protection Agency (EPA) 

regulates pesticide use in the United States. Several 

chemical formulations are registered with the 

EPA for the treatment of soil to prevent termite 

attack. The chemicals available for use vary over 

time. Such factors as economics, human safety, 

environmental hazards, and Federal regulation 

determine which pesticides may be used, and by 

whom. Some pesticides may be purchased and used 

by the homeowner, but most require certification 

by the State and a license to purchase and use. 

Additionally, individual States may impose further 

regulations or recommendations specific to their 

area. Be sure to check with your State authorities 

before attempting to use a pesticide product.

Note: The following sections are provided for 

information purposes only. They are intended to 

give a better understanding of how soil treatments 

for termite control are used. They are not meant 

as a substitute for the label of any product. Be 

aware that many termite control pesticides are 

limited to use by only State-licensed termite control 

applicators. Always read and follow

label directions. It is unsafe, ineffective, 

and a violation of Federal law to use a pesticide in a 

manner other than prescribed on the label.

Figure 19. — Construction of wooden steps to prevent hidden termite attack.
19

Preparation of chemical solutions—A soil 

chemical is often purchased as a liquid 

concentrate. The concentrate is formulated 

according to the percentage, or weight in pounds 

per gallon, of the insecticide it contains. Each 

concentrate contains inert ingredients that improve 

application and performance, and it must be diluted 

before use. Some compounds are purchased as 

a wettable powder that dissolves or becomes 

suspended when mixed with water. Wettable 

powders contain several inert ingredients also. 

Neither powders nor concentrates provide better 

termite control. The form the pesticide comes in 

is determined by manufacturing considerations. 

Directions are given on the container for diluting 

the concentrated solution to the desired strength. 

The label directions must be followed exactly. 

Rates and methods of application—The objective 

of treating soil with chemicals is to provide a 

continuous chemical barrier in soil surrounding the 

building foundation. The chemical must be applied 

thoroughly and uniformly to block all routes of 

termite entry. This requires that the treatment be 

applied at all potential termite entry points. The 

rates and methods of application vary with the type 

of construction.

1. Crawlspace houses (conventional 

foundation)—The soil under and around crawl 

space houses should be treated as follows:

a. Four gallons (15 liters) of diluted chemical 

are applied per 10 linear feet (3 m) of 

trench along the inside of all foundation 

walls and along all sides of interior 

supports and plumbing (figs. 20 and 21).

b. A trench 6 to 8 inches (15 to 20 cm) wide 

is dug along the outside of the foundation 

(including the soil beneath porches and 

patios before the concrete is poured). Where 

the top of the footing is more than 12 inches 

(30 cm) deep, holes will be made in the 

soil at intervals no greater than 12 inches 

(30 cm) to the top of the footing. The holes 

may need to be closer together in hardpacked clay soils than in light sandy soils. 

Four gallons (15 liters) of diluted chemical 

are applied to 10 linear feet (3 m) of trench 

for each foot (30 cm) of depth from grade 

to footing. The soil is saturated with the 

chemical as the trench is being refilled.

c. If an attached porch, carport, or other 

structure contains wood, the soil beneath 

the slab should be treated with 1 gallon 

(4 liters) for 10 square feet (1 m2) before 

the concrete is poured. This is to prevent 

termites from gaining access to the main 

structure through wood in the attached 

structure.

2. Slab-on-ground construction—This type of 

construction should be treated with a registered 

termiticide after any backfilling, leveling, and 

tamping of the soil and before the concrete is 

poured. The chemical is applied with a power 

sprayer using low pressure to avoid misting and 

off-target drift. 

a. Where the fill is soil or unwashed gravel, 

1 gallon (4 liters) of diluted chemical per 

10 square feet (1 m2) of area is applied as 

an overall treatment under the slab and any 

attached slab porch, carport, garage, and 

terrace (fig. 22).

b. If the fill is washed gravel or other coarse 

absorbent material, such as cinder, 1.5 

gallons (6 liters) are applied per 10 square 

feet (1 m2) to ensure penetration of the 

termiticide to the soil beneath.

c. In critical areas under the slab, such as 

along the inside of foundation walls, along 

both sides of interior partition walls, and 

around plumbing, 4 gallons (15 liters) of 

diluted chemical are applied to the soil per 

10 linear feet (3 m).
20

d. Voids in masonry blocks or foundations may 

be treated as well. If the voids are inaccessible, it may be necessary to drill holes near 

the footing and inject a chemical to form 

a continuous barrier. Two gallons (8 liters) 

of diluted chemical are applied to 10 linear 

feet (3 m) of wall or foundation (fig. 23). 

Do not apply a termiticide to wall voids 

filled with rigid foam insulation.

e. After the slab is poured, a trench 6 to 8 inches 

(15 to 20 cm) wide is dug along the outside 

of the foundation (fig. 20). Where the top of 

the footing is more than 12 inches (30 cm) 

deep and where large volumes of chemical 

must be applied, holes are made about 12 

inches (30 cm) apart in the bottom of the 

trench to the top of the footing using a soil 

auger, crowbar, metal rod, or grouting rod. 

These holes permit better distribution of 

the chemical by providing access to the soil 

at depths below the trench. The holes may 

need to be closer together in hard-packed 

clay soils than in light sandy soils. Four 

Figure 21. — Application of a chemical to crawlspace construction. Soil treatment is applied (1) alongside outside wall, 

(2) inside wall, (3) around pier, and (4) around plumbing.

Figure 20. — Application of a chemical to soil around a 

foundation.
21

Figure 22. — Chemical treatment of fill material before 

slab is poured.

gallons (15 liters) of diluted chemical are 

applied to 10 linear feet (3 m) of trench 

for each foot (30 cm) of depth from grade 

to footing. The soil is saturated with the 

chemical as the trench is filled.

3. Basement houses—The soil under and around 

houses with basements should be treated as 

follows:

a. The soil under and around basement 

houses is treated in the same manner 

as recommended for slab-on-ground 

construction (figs. 22 and 24).

b. Voids in masonry foundations may be 

treated at or near the footing with 2 gallons 

(8 liters) of chemical per 10 linear feet (3 m) of 

wall. Do not apply a termiticide if the voids 

have been filled with rigid foam insulation.

Figure 23. — Application of chemical to slab construction.
22

4. Other types of construction—It is not 

possible to list in detail all the various types 

of construction available. However, treatments 

should be made according to the individual 

component parts, using the specifications that 

apply to each.

Considerations when treating new construction—

The type of soil encountered at the building site and 

the amount of moisture present in the soil just prior 

to treatment will have an effect on the acceptance 

of liquids at the recommended rates. A soil fill will 

best accept a treatment when it is damp but not 

excessively wet or dry. Most product labels prohibit 

application to saturated or frozen soil. If the soil 

is excessively wet, there is a chance of runoff, and 

the chemical will not penetrate the soil. In frozen 

or excessively dry soil the chemical solution is 

repelled and puddling occurs, resulting in poor 

distribution of the termiticide. 

Mechanical disturbance of treated soil breaks the 

continuity of the insecticide barrier and increases 

the probability of termite penetration. The treatment 

of fill under slabs is less than 2 inches (5 cm) deep 

and the majority of the material is in the top 3/4 inch 

(2 cm); therefore very little disturbance to the 

treated soil can be tolerated. The final treatment on 

the outside of the foundation walls should be done 

after all grading and other soil disturbance has 

been completed. A freshly treated slab foundation 

site should be protected with a polyethylene sheet 

or other waterproof material. This will prevent rain 

from washing away the insecticide or treated soil. 

Any disturbance of treated soil, even years after 

treatment, can disrupt the integrity of the termiticide 

barrier. Laying of pipes, cables, phone lines, etc., 

into a house through the treated barrier can disrupt 

the barrier, and disturbed soil should be retreated 

Figure 24. — Application of chemical in basement construction: (A) treatment along foundation, (B) rodding to top of 

footing, (C) treatment of fill below slab, and (D) slab poured after fill has been treated.
23

once the work is finished. Landscaping practices 

near the foundation wall may disrupt the barrier 

and make inspections more difficult. Care should 

be taken when planting shrubs or other plants that 

the treated area is not disturbed. Landscape timbers 

placed over a treated zone may provide a bridge for 

termites to bypass the barrier and gain entrance into 

the house. Use treated lumber for such purposes, 

and make sure the wood does not come in direct 

contact with the house. 

The termiticide is stable once it dries on the soil. 

Because most commonly used termiticides are 

insoluble in water, leaching is not a problem. There 

is a slight risk, however, of contaminating a well 

or other water supply if insecticides are applied to 

nearby soil that either contains layers of gravel or 

tends to crack severely in periods of dry weather. 

In these situations, the soil should not be treated 

with chemicals and other control methods should 

be used. 

Many termiticides are extremely toxic to fish 

and other aquatic organisms. Therefore, special 

care must be used to avoid insecticide drift when 

treating buildings near bodies of water. Care should 

also be used if there is a chance of treated soil 

washing into a pond or stream if it rains before 

the slab is poured. Do not apply a termiticide if 

precipitation is likely. 

Naturally resistant woods—Untreated sapwood 

is highly susceptible to termites and has a short 

service life when termites are allowed access to 

it. However, the heartwood of some tree species 

has varying degrees of termite resistance. This 

resistance is attributed to chemical components 

produced naturally by the living tree that are toxic 

and/or repellent to the termites. The practice of 

using resistant woods has been almost completely 

replaced in the United States by using chemicals to 

protect wood. Even the most resistant wood is not 

completely immune to attack, because termites will 

still eat resistant wood if a preferred wood is not 

available. 

Different woods vary in their relative resistance 

to termites. Some species typically considered 

resistant are bald cypress, eastern red cedar, 

chestnut, Arizona cypress, black locust, redwood, 

Osage orange, black walnut, and Pacific yew. It 

should be noted that even the most resistant 

woods cannot be considered termite barriers. 

Termites can tube over resistant wood and attack 

susceptible wood. Generally, the use of resistant 

wood throughout a structure can be economically 

justified only when drywood termites or decay are 

considered serious problems and protection from 

them is necessary. 

Chemically treated woods—Chemically treated 

wood safeguards against both termites and decay. 

The degree of protection obtained depends on the 

kind of preservative, the penetration achieved, and 

the retention of the chemical in the wood. Woods of 

various species and types differ in their ability to be 

treated, and the heartwood resists treatment more 

than the sapwood. 

The life of wood structures can often be increased 

by applying wood preservatives at standard retention rates and ensuring that the wood is satisfactorily penetrated. For maximum protection, the wood 

should be pressure treated with an approved chemical by a standard process. In less severe conditions, 

a vacuum treatment usually gives adequate protection. Brush, spray, or short-period soak treatments 

only give limited protection of wood above ground 

and should not be relied upon to give long-term protection from termite attack.

As with the naturally resistant woods, termites are 

able to tube over treated wood and attack untreated 

wood. Again, because of cost, only where drywood 

termites and decay are a problem should chemically 

treated wood be used throughout a structure.
24

Control of Subterranean Termites in Existing Buildings

Ridding existing structures of termites and making 

them resistant to future infestations are major 

problems in termite control. Generally, buildings 

become infested because little or no attention 

was given during construction to the preventive 

measures that would have made the structures 

resistant to termites. It is in such buildings that 

termites cause heavy losses each year.

Observe the same principles that are recommended 

for the prevention of infestations in new buildings 

when controlling termites in existing buildings. 

That is, eliminate conditions favoring the 

development of termite colonies in the soil and 

permitting passage of termites to wood within the 

structure. Subterranean termites in the wooden 

parts of a building will die if they are unable to 

maintain contact with the soil or other sources of 

moisture. 

Inspection

Regardless of previous preventive measures, 

wooden structures should be inspected 

periodically for evidence of active infestation. If 

no preconstruction measures were employed, the 

structure should be inspected more frequently. 

Under certain circumstances, termites may 

breach even the best physical barriers, and even 

insecticides may be ineffective in stopping termites. 

The continuity of the termite barrier may be 

broken, and maintenance or repair personnel may 

leave a condition that favors termite infestation 

after working underneath or around the structure. 

A homeowner can inadvertently disturb the treated 

soil or place wood on the soil against or under 

the building. If not cautious, the homeowner may 

overlook vegetation that has grown over or through 

the chemical barriers, providing access for termites. 

Settlement cracks may occur in the foundation walls 

or concrete slabs and allow termite entrance.

With proper inspection, very little termite damage 

should result before discovery. Termites typically 

work slowly and can be detected and controlled 

before causing structural weakness to the timbers. 

Although extreme haste is not required, once an 

infestation is discovered, treatment should be 

applied within a few months.

Sanitation

Sanitation and structural control measures should 

be given consideration in the control of existing 

infestations. In addition to chemical treatments, the 

following control measures should be used:

1. Remove all wood, including form boards 

and other debris containing cellulose, from 

underneath and adjacent to buildings. 

2. Remove exterior wooden structures, such as 

trellises, that connect the ground with the 

woodwork of the house. Any wood remaining 

in contact with the soil should be treated with 

preservative. 

3. Replace heavily damaged (structurally weakened) 

sills, joists, flooring, etc., with sound wood. 

Where possible, remove all soil within 18 inches 

(46 cm) of floor joists and 12 inches (30 cm) of 

girders (fig. 10).

4. Fill voids, cracks, or expansion joints in 

concrete or masonry with cement or roofinggrade coal-tar pitch.

5. Provide adequate drainage (see pages 9 through 

10).

6. Provide access for inspection of vulnerable 

areas.
25

7. Provide adequate foundation ventilation 

in crawlspace construction. A barrier of 

polyethylene or similar material should be 

placed on the soil to retard moisture. 

Chemical Control

Chemicals used to prevent termite infestations are 

sometimes also used to control existing infestations 

in buildings. The rates of application, method 

of preparation, and necessary precautions are 

discussed on pages 17 through 23.

The many variations in construction prevent 

a detailed discussion of exact procedures for 

chemical treatment in all situations. In applying 

treatments, however, remember that the purpose 

is to establish a chemical barrier between 

termites in the soil and wood in the structure or 

to reestablish the barrier if it has been broken. It is 

best to have this work done by a professional. Some 

procedures for treatment of existing buildings are 

as follows:

1. Crawlspace construction—Buildings with 

crawlspaces usually can be treated easily and 

effectively. The procedures recommended 

for pretreatment can also be used for termite 

control in existing buildings (see pages 19 

through 20).

2. Slab-on-ground construction—Termite 

infestations in buildings with this type of 

foundation present serious control problems. It 

is difficult to form an effective chemical barrier 

in the soil beneath such floors. One way to treat 

under a slab is to drill a series of vertical holes 

about 0.5 inch (1.2 cm) in diameter through the 

slab and into the soil beneath, particularly at the 

base of partition walls and other points where 

the termites may be entering (fig. 25). In most 

cases, holes should be no more than 12 inches 

(30 cm) apart. Because a complete barrier is 

necessary for the treatment to be effective, the 

chemical injected into each hole must meet with 

that injected in adjacent holes. The advantage of 

vertical drilling is that the chemical will flood 

and cover the surface of the soil.

Figure 25. — Treatment under a concrete slab with vertical rodding to reestablish the chemical barrier.
26

Another way to treat under slabs is to drill 

horizontally through exterior foundation walls to 

the soil just beneath the slab and inject the chemical 

in the holes. This method is complicated, requires 

special equipment, and should be performed only 

by a professional. Extreme caution should be 

taken to prevent drilling into plumbing, electrical 

conduits, or heating ducts that may be imbedded 

in concrete. Injection of termiticides into these 

areas must be avoided. Always treat along the 

outside of the foundation (see pages 19 through 21).

3. Basement construction—Treat the soil along 

the outside walls of basements (see page 21).

4. Raised porches, terraces, and entrance 

slabs—Termite infestations frequently occur at 

porches, terraces, and entrance slabs. The most 

satisfactory way to control infestations at these 

locations is to excavate the soil adjacent to the 

foundation wall, remove all wood debris, and 

apply a chemical to the soil as recommended. 

Place an access panel over the foundation 

opening to permit inspection. Alternatively, 

holes may be drilled either through the adjacent 

foundation wall from within the crawlspace 

or basement, or through the entrance slab at 

intervals no larger than 12 inches (30 cm). 

Chemicals should be injected to form a 

continuous barrier.

5. Buildings with wells, cisterns, sump pumps, 

French drains, or irrigation systems—

Although most termiticides are not very soluble 

in water once they have dried to the soil, during 

application the chemical can be washed or 

blown into a well, cistern, or drainage system. 

Where wells are located close to or within 

foundation walls, care must be taken to avoid 

contamination of the well or cistern. If the 

label allows, the treated backfill method may 

be used. The soil around the well or cistern 

is removed onto a heavy plastic sheet or into a 

wheelbarrow. The termiticide formulation is 

applied at a rate equivalent to 4 gallons (15 liters) 

of diluted chemical to 10 linear feet (3 m) of 

trench for each foot (30 cm) of depth. The 

termiticide is thoroughly mixed into the soil and 

the soil is replaced into the trench. 

Some termiticide producers caution against using 

their product near sump pumps and French drains. 

A termiticide may usually be applied near a sump 

pump if the water level in the pit is not rising. The 

soil around French drains usually may be treated 

if the soil is dry. For sump pumps and French 

drains, the treated backfill method may be used if 

desired. Do not apply a termiticide if precipitation 

is likely, and do not use irrigation systems until the 

termiticide has had time to dry. 

Termiticidal Baits

Several termite bait applications have become 

popular in recent years. Baiting technology relies 

on certain biological principles. Termites, being 

social insects, are known to feed each other, and 

termites foraging on a treated substance (paper, 

cardboard, etc.) can transfer a portion of the active 

ingredient to nestmates (fig. 26). The idea is that 

not all termites need to encounter the bait itself 

to be killed. Some baits may be purchased and 

used by homeowners, others need to be installed 

and monitored by licensed professionals. Baits 

are applied in the same manner regardless of 

construction type.

Most currently available baits employ the placement of untreated monitor stations around or near a 

structure (fig. 27). The placement is determined by 

the manufacturer’s instructions. Here, the termite 

presence may be detected before the termites enter 

a structure. Most monitoring stations consist of a 

plastic tube with holes or slits cut to allow termite 

entry. Within the station is a food source, often 
27

Figure 26. — Termite bait is taken by termites and then shared with others in the colony.

Figure 27. — Bait stations placed along the perimeter of a house (number shown is less than that typically 

recommended by the manufacturers).
28

wood, paper, or cellulose powder. The stations are 

monitored on a schedule and, once termites are 

detected in the monitoring stations, the toxic bait is 

added. The bait may or may not be in the same form 

as the monitoring material. The stations continue to 

be monitored and new bait added until termite activity 

stops for a specified amount of time, such as 1 year. 

Once this happens, the bait station is removed and 

replaced with a new monitoring station. 

The active ingredients of some baits are insect 

growth regulators that interrupt important processes 

in the insect’s life, such as the shedding of skin. As 

a result, they are usually specific to insects with few 

effects on noninsect life. However, because they interfere only with certain stages, it may take weeks, 

months, or even years to control an infestation. 

Other baits use metabolic poisons, which affect a 

specific point in the termites’ energy cycle.

Baits may be used alone, or in conjunction with 

chemical treatments. Care should be taken to ensure 

that chemicals do not contaminate the monitoring/

bait stations. Such contamination may cause the termites to avoid the monitoring station, allowing them 

to go undetected. Also, care should be taken when 

using lawn care and landscaping pesticides in areas 

where bait monitoring stations may be present. 

Because most homeowners cannot afford to use 

both chemical and bait treatments, the question 

arises as to which technology is preferable. This 

will depend on the homeowner’s preferences. 

Both chemical treatments and baits are popular. 

Table 1 describes some important advantages and 

disadvantages of baits and chemical termiticides.

Baits Liquid termiticides

Lower amounts of chemical are used—ounces (g) versus 

gallons (liters).

Large amounts of chemical are used—gallons (liters).

Require ongoing service contract—protection ends the day 

the contract is cancelled or expires and bait is removed.

Do not require ongoing contract—single treatments 

are effective for years (periodic inspections are still 

recommended).

Specific to insects (IGRs)—fewer environmental concerns. More general poisons—more hazardous to the 

environment if used incorrectly.

Role in preconstruction applications uncertain. Effective in preconstruction applications.

Slower acting—require weeks or months to be effective. Faster acting—insects die in hours or days after 

encountering toxicant.

Less disruptive to property to install. More disruptive to property to install.

Sharing of bait spreads toxicant through colony. Some compounds show spread through colony.

Table 1. — Comparison of the advantages and disadvantages of baits and soil-applied liquid termiticides.

IGR = insect growth regulator.
29

Other Insects That Damage Wood in Buildings

Other insects attack wood in buildings, and their 

damage may be mistaken for that caused by 

subterranean termites. The insects most commonly 

involved are drywood termites, wood-destroying 

beetles, carpenter ants, and carpenter bees. 

The work of these insects differs from that of 

subterranean termites in that the wood they attack is 

converted either to compressed pellets, powder, or 

shredded fibers. In contrast, subterranean termites 

leave small, grayish-brown specks of excrement 

in excavated areas. Subterranean termite galleries 

follow the grain of the wood, whereas the tunnels 

of most of the other insects mentioned usually cut 

across the grain.
30

Risk Factors for Termite Problems—A Checklist

Any items checked “yes” below should receive special attention at inspections and be checked more 

frequently. If possible, the problem should be corrected. 

Are there...

Yes/No Cracks in concrete foundation?

Yes/No Posts in concrete?

Yes/No Earth-filled porches? 

Yes/No Form boards left in place after construction?

Yes/No Leaking pipes or faucets? 

Yes/No Shrubs near air vents?

Yes/No Wood debris underneath or around the house? 

Yes/No Low foundation walls or footings? 

Yes/No Brick veneer covering foundation? If bond fails, termites have hidden access.

Yes/No Flower planters near foundation walls? 

Yes/No Wooden forms around drains? 

Yes/No Porch steps in contact with the ground? 

Yes/No Obstructions around heating unit? 

Yes/No Paper collars around pipes? 

Yes/No Trellises? Do they touch the soil?

Yes/No Rigid board insulation, stucco, or siding that extends all the way to the soil?
31

Acknowledgments

Colorized line drawings were prepared or redrawn 

by Beth Dishongh, Mississippi State University, 

Office of Agricultural Communications, Mississippi 

State, MS. Photographs for figures 6 and 7 were 

taken by Tom Murray, Boxborough, MA. Figure 

22 was photographed by Tim Lockley, Mississippi 

Bureau of Plant Industry, Mississippi State, MS. 

The use of trade or firm names in this publication 

is for reader information and does not constitute 

endorsement by the U.S. Department of Agriculture 

for any product or service.
32

Pesticide Precautionary Statement

Pesticides used improperly can be injurious to 

humans, animals, and plants. Follow the directions 

and heed all precautions on the labels.

Store pesticides in original containers—out of reach 

of children and pets—and away from foodstuffs.

Apply pesticides selectively and carefully. Do not 

apply a pesticide when there is danger of drift 

to other areas. Avoid prolonged inhalation of a 

pesticide spray or dust. When applying a pesticide it 

is advisable that you be fully clothed.

After handling a pesticide, do not eat, drink, or 

smoke until you have washed. In case a pesticide 

is swallowed or gets in the eyes, follow the first aid 

treatment given on the label and get prompt medical 

attention. If the pesticide is spilled on your skin or 

clothing, remove clothing immediately and wash 

skin thoroughly.

Dispose of empty pesticide containers by wrapping 

them in several layers of newspaper and placing 

them in your trash can.

It is difficult to remove all traces of an herbicide 

(weed killer) from equipment. Therefore, to prevent 

injury to desirable plants do not use the same 

equipment for insecticides and fungicides that you 

use for an herbicide.

Note: Registrations of pesticides are under constant 

review by the Environmental Protection Agency 

(EPA). Use only pesticides that bear an EPA 

registration number and carry directions for home 

and garden use.

The U.S. Department of Agriculture Forest Service is dedicated to the principle of multiple use 

management of the Nation’s forest resources for 

sustained yields of wood, water, forage, wildlife, 

and recreation. Through forestry research, cooperation with the States and private forest owners, and 

management of the national forests and national 

grasslands, it strives—as directed by Congress—to 

provide increasingly greater service to a growing 

Nation.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on 

the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial 

status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because 

all or part of an individual’s income is derived from any public assistance program. (Not all prohibited 

bases apply to all programs.) Persons with disabilities who require alternative means for communication of 

program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 

720-2600 (voice and TDD). To file a complaint of discrimination, write USDA, Director, Office of Civil 

Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410, or call (800) 795-3272 (voice) or 

(202) 720-6382 (TDD). USDA is an equal opportunity provider and employer.