

Subterranean termites are the most destructive wood insect pests.

They cause more than $1 billion damage in the United States. In

nature, termites scavenge wood, breaking down dead trees, branches

and the wood which accumulate in forests. The breakdown products of

wood are returned to the soil as humus. Problems begin when

termites invade human structures. Unfortunately by the time the

termites are seen the damage is already done. Homeowners should

practice prevention. Successful chemical control almost always

requires the services of a qualified pest control operator.



Termites are social insects. Several types make up a colony, each

one serving the colony in a different way. Winged reproductives

swarm from mature colonies to disperse and establish new colonies.

Worker termites, the ones that damage wood by eating the softwood

layers, are white and soft-bodied. They feed the other forms in the

colony and expand the nest size. Soldier termites, equipped with

enlarged mandibles, are responsible for protecting the colony from

intruders. In arid areas another type of soldier, the nasuti,

recognized by its pear shaped head, is a chemical warrior that

releases a sticky substance to entrap enemies.



Ants and termites are similar in appearance and are often confused.



When and How to Check for Damage



A termite's natural habitat includes stumps, post, and other wood

that comes in contact with the ground. Though termites may be found

in these materials near the home, it does not necessarily mean the

home is or will be infested.



Termites need wood for food and soil for moisture. Wood in contact

with soil, then is ideal for termite development. Natural wood

serves as food and homesites. These soil-dwelling insects may

bridge gaps by building "mud tubes" to reach foundation walls and

other masonry that separate the wood from the inside them in voids

or cracks. Occasionally, when a leaky roof or pipe provides

moisture, termites can invade without solid contact with the soil.



To check for termites, any wood near the foundation or soil should

be probed with an ice pick or screw driver, especially the plates,

header joists, ends of floor joists and any hardwood flooring.

Presence of earthen "shelter tubes" on foundation walls and wood is

also evidence of infestation. The tubes will resemble long streams

of mud running up basement walls or along foundations. The tubes

are generally less than 1/4 inch in diameter. Wider tubes indicate

a more serious infestation.



Remember, infestations develop in soil. The termites enter the

building through structural wood or foundation walls adjacent to

the soil. In the case where houses are built partly or completely

on slabs, infestation is through expansion joints, cracks and

utility and sewer openings.

If damage is found, there is no great hurry to apply control

measures. Termites work slowly, and a few weeks delay is of little

consequence.



TERMITES
Talking to a Pest Control Operator (PCO)

Whether pretreating at the time of construction or treating an
existing structure, the basic principle of termite control is to
break the connection between wood and soil. This is done by laying
down a chemical barrier to eliminate all possible points of entry.
In view of the rather elaborate equipment required and the
complicated nature of the process, it is strongly suggested that
the homeowner consult a professional pest control service.

Some Suggestion When Dealing with a PCO:

Don't panic. There is no need to become frightened or unduly
alarmed if you learn that termites may be attacking your home.
These insects work slowly, and your house will not be ruined or
collapse overnight.

Take your time. Do not permit anyone to rush you into purchasing
termite control service. Delay of a few weeks will not make any
difference. Take time to purchase this service wisely.

Purchase services from a reliable firm. Buy termite control service
with the same care and discrimination that you would use in the
purchase of any other service for your property. Be sure you are
dealing with a reliable firm.

Does the company have association membership? Membership in the
Delaware Pest Control Association, Inc., or the National Pest
Control Association, is evidence that a firm has an established
place of business. Membership lists of these associations may be
obtained by writing or calling your local cooperative Extension
office or the National Pest Control Association, 8011 Oak Street,
Dunn Loring, VA 22027.

Know the terms of the contract. Ask your PCO to provide you with a
written statement of the work he/she proposes to do and the cost.
It is customary to guarantee termite control work, either on a
year-to-year basis or for a 5-year period. Make sure you understand
what guarantee is offered by the firm.

Check the guarantee. A guarantee is no better than the person or
the firm who gives it to you. A guarantee is not evidence that a

firm is reliable. Determine if a yearly charge will be levied
during the guarantee period or whether this charge is included in
the initial price of the job.

And finally. You will probably be asked to sign a work order when
you engage a firm. Understand clearly what obligations you are
assuming and what you are getting in return.

PRETREATMENTS

Homes and other buildings can be pretreated at time of construction
to protect them against termite attack. Pretreatment is relatively
inexpensive and highly desirable, especially for buildings
constructed completely or partly on concrete slabs. Slab buildings
are very susceptible to termite attack, and once they are infested,
treatment is difficult and expensive.

Since the chemical barrier needs to be under the concrete slab, it
is much easier to lay a chemical barrier before the concrete is
poured than it is afterwards.

Areas Needing Pretreatment For effective termite prevention,
pretreatment is needed in four areas during construction:

1. Treatment of the entire soil surface under any area to be
covered with concrete, including garage floors, entrance platforms
and filled porches. 

2. Re-treatment with additional amounts of chemical to the soil
beneath those areas which lie adjacent to foundation walls, beneath
interior walls, around sewer and utility openings and at other
possible points of entry. 

3. Treatment of footings and backfill outside foundation walls and
inside walled areas where there is a crawl space. Accessible areas
like these could be treated later, but it's easier to do it at
construction time.

4. Treatment of empty spaces or voids in
concrete blocks.

Approved Pretreatment Chemicals

Chemical pretreatment is accepted by the FHA as a method of termite
proofing. Most pest control specialists are equipped to pretreat
according to FHA specifications, and they can guarantee
effectiveness. Contractors and others may not provide this
guarantee.

Dursban should be used for pretreatment termite control. It is
applied in liquid form. It is necessary to dilute the chemical to
obtain the correct concentration. The user should start with an
emulsifiable concentrate, reading the label to determine the
percentage of actual chemical present. The concentrate should be
diluted with water to obtain a 1 percent concentration. For example
Dursban REC is a 4-pound-per-gallon liquid that is 48.8 percent
active ingredient. To make a 1 percent solution it should be
diluted with 49 parts water to 1 part product.

Other Pretreatment Measures

Other helpful measures are to make sure no wood comes in contact
with soil and all wooden foundation forms, stakes, stumps and
scraps of wood are removed from the area before it is covered with
dirt or concrete. Also, the soil surface in unexcavated areas
should be cleared of wood scraps.

Capping concrete block foundations with a 4-inch solid block gives
added protection, provided the cap blocks are joined tightly and
there are no openings in the mortar.

TREATMENT IN EXISTING FACILITIES

If you intend to do a termite control job yourself, you must
understand the problem and the solution. If the method of
infestation is unclear, it will probably save you time, money and
stress to engage a professional; foundation.) To avoid structural
damage, do not dig the trench below the top of the footing.

the expense of a PCO may be less than you expect.

Consider the type of construction in the structure where you wish
to control termites. Does your house have a basement? A crawl space
only? Or is it on a slab foundation? Next, determine where to best
create an insecticide barrier between the house and the termite
colony.

Recommended Chemicals

The only approved chemical for soil treatments is chlorpyrifos
(Dursban available to homeowners as Ortho-Klor). A PCO will likely
use DursbanR, which is labeled for limited use by PCOs, or Pryfon
which is similarly limited. Chlordane and other chlorinated
hydrocarbons, widely used in the past for termite control, are no
longer labeled for use as termiticides. PCOs also can use
pyrethroid compounds which are not available to the homeowner to
treat the soil or infested wood

Structures with different constructions are treated in different
ways. The three major types found in our area are discussed
separately below:

BUILDINGS WITH CRAWL-SPACE-TYPE FOUNDATIONS

This type construction can be treated fairly easily and effectively
because the foundation can be surrounded with the insecticide
barrier.

First dig trenches 6 to 8 inches wide adjacent to and around all
piers or supports and pipes, and along both the inside and outside
of all foundation walls. Where the footing is more than 12 inches
deep, make crowbar, pipe, or rod holes no more than 1 foot apart;
extend them from the bottom of the trench to the footing. (This
will prevent termites from gaining hidden entry to the building
through voids.)

Next pour the pesticide into the trench at the rate of 4 gallons
per 10 linear feet for each foot of depth. If the trench is a deep
one, apply the chemical to alternate layers of about 6 inches of
soil the trench is refilled. It is important to trench all pipes,
beams, etc., that go from soil to structure.

BUILDINGS WITH BASEMENT FOUNDATIONS

Basements are treated like crawl-space houses except only the
outside has to be treated. Treat deeper though, and use specialized
equipment to do the job properly.

To treat the soil along the outside walls of a basement, dig a
trench 6 to 8 inches wide and a foot or more deep adjacent to the
wall. Then make crowbar, pipe, or rod holes no more than 1 foot
apart that extend from the bottom of the trench all the way to the
footing. Pour the chemical into the trench at the rate of 4 gallons
per 10 linear feet for each foot of depth from grade to footing,
alternately replacing and treating 6-inch layers of soil.

Some houses have both crawl-space and basement foundations. The
basement end next to the crawl space can be difficult to treat, but
it must be done.

Additions to Structures--Areas particularly vulnerable to termite
attack are raised door stoops and attached structures such as
carports, porches and walkways. Be sure the soil adjacent to the
foundation is treated. Don't go around a door stoop or other
attachments. It is best to knock a hole in each side of the stoop
and clean the dirt, especially any wood, out of the area. Then put
louvers in the holes so this area can be dried out and checked
periodically. If no other method is possible, the stoop should be
drilled along the side next to the house and the holes rodded down
about 8 inches apart. Sometimes these stoops can be cleaned out by
coming through the foundation from the inside of the house. A
cement walk or a carport directly adjacent to the building being
treated offers a similar problem. Drill holes next to the building
(through the cement), penetrate with rods and treat.

BUILDINGS WITH SLAB-ON-GROUND FOUNDATIONS

Termite infestations in houses built with a slab on the ground
present the most difficult control problems. While the structural
damage to the actual supporting members of the house may not be as
critical as it could be to a crawl space house, it is difficult to
treat the soil underneath the slab in a way to protect the wooden
plate and wall studs. The best way to do this is to drill holes
about 1/2 inch in diameter through the concrete slab, close to the
points where the termites are or where they may be entering.

Space the holes about 6 inches away from the wall and about 12
inches apart to ensure proper treatment of the soil underneath.
Take care to avoid drilling into plumbing and electric conduits.
Apply the chemical through the holes. Another way is to drill
through exterior foundation walls to the soil just underneath the
slab and apply the chemical through these holes. This method is
complicated, however, and usually requires concrete drills and
pressure treatment, using soil rods and other special equipment. In
cases of actual infestation, you are strongly urged to contact a
PCO when this type of construction is involved.

OTHER PRECAUTIONS

Along with the actual control job, several things should be done to
prevent another infestation.

1. Remove all wood, including form boards and other debris
containing cellulose, from underneath and adjacent to buildings
with crawl spaces. 

2. Remove other wooden items, such as trellises, that connect the
ground with the woodwork on the exterior of the building. Only
replace them after you break contact between soil and wood.
Chemically impregnate or treat around  wood  posts that will be
driven into the soil.

3. Replace heavily damaged structurally weakened) sills, joists,
flooring, etc., with sound material. Where possible, remove all
soil within 18 inches of floor joists and 12 inches of girders.

4. Fill voids, cracks or expansion joints in concrete or masonry
with either cement grout, roofing-grade coal-tar pitch or rubberoid
bituminous sealers.

5. Provide adequate drainage and ventilation.

Author:
Dewey M. Caron
University of Delaware
Cooperative Extension Entomologist
.
