Subterranean Termites
P. G. Koehler and C. L. Tucker2
The three principal types of termites are subterranean (nest in
the soil), dampwood (infest damp wood), and drywood termites (infest dry
wood). Subterranean termites ( Figure 1 ) are the most destructive and
frequently encountered kind of termite found throughout the state. Although
they nest in soil, subterranean termites can attack structures by building
tubes that connect their nest to wood in structures. Aerial nests can occur
without a ground connection if all castes of the colony are present and
moisture is available
.
CREDITS: James Castner, University of Florida
Figure 1. Eastern subterranean termite.
Biology
Subterranean termites are social insects that live in colonies consisting
of many individuals. The colonies are composed of workers, soldiers and
reproductives (Figure 2 ).
CREDITS: University of Florida
Figure 2. Castes of termite from top left, right and bottom; worker,
soldier, and winged reproductive.The workers, which are about 1/8 inch long, have no wings, are white to cream colored and very numerous. Soldiers defend the
colony against insects, like ants, that can attack the colony. Soldiers are
wingless and white in color with large brown heads and mandibles (jaws). King
and queen termites perform the reproductive functions of the colony. They are
dark brown to black in color and have two pairs of wings about twice the
length of their body. See Figure 3 for the termite life cycle.
CREDITS: University of Florida
Figure 3. Termite life cycle.
Subterranean termites feed on wood or other items that contain cellulose,
such as paper, fiberboard, and some fabrics derived from cotton or plant
fibers. Termites have protozoa in their digestive tracts that can convert
cellulose into usable food.
Subterranean termites nest in the soil to obtain moisture, but they also
nest in wood that is often wet. They easily attack any wood in contact with
the ground. If the wood does not contact the soil, they can build mud tunnels
or tubes to reach wood several feet above the ground. These tunnels can extend
for 50-60 feet to reach wood and often enter a structure through expansion
joints in concrete slabs or where utilities enter the house.
Detection of Termites
Termites remain hidden within wood and are often difficult to detect.
However, subterranean termites may be detected by the presence of winged
reproductives, mud tubes, and wood damage.
Winged Reproductives
Winged reproductives ( Figure 4 ) emerge from colonies in great numbers
usually in the spring and during the daylight hours. Usually termites are
first noticed by the presence of winged reproductives. Mating occurs during
these flights, and males and females form new colonies. Winged termites can be
distinguished from flying ants by their thick-waist, straight antennae and
wings of equal size. See Figure 5
.
CREDITS: James Castner, University of Florida
Figure 4. Winged reproductive subterranean termite.
CREDITS: University of Florida
Figure 5. Subterranean termite (top) and winged ant (bottom) reproductive.
Termites have thick waists, straight antennae, and wings of equal size.
Large numbers of winged termites in a house are an indication of probable
infestation. Termite wings break off shortly after their flight, and even
though the actual swarming is not observed, the presence of discarded wings
indicate that a colony is nearby. Because termites are attracted to light,
their broken-off wings are often near doors or windows where the termites have
been attracted to the light.
Winged termites emerging from the ground out-of-doors near the house does
not necessarily mean the house is infested, but it is a good reason to check
further. Termites in the wood of homes or other buildings usually come from
colonies already established in the soil.
Peak swarming periods for subterranean termites are from January through
May in Florida. They may also swarm to a lesser extent during the other
months.
Mud Tubes
Subterranean termites build earthen, shelter tubes to protect them from
low humidity and predation (Figure 6 ). These tubes are usually 1/4 to 1 inch
wide. Houses should be inspected at least once a year for evidence of tubes.
If the house has a crawl space, the inside and outside of foundations should
be inspected for tubes. If the house has a concrete slab floor, cracks in
concrete floors and places where pipes and utilities go through the slab
should be closely examined. Cracks in concrete foundations and open voids in
concrete block foundations are also hidden avenues of entry.
CREDITS: University of Florida
Figure 6. Mud tubes connect the colony in soil with wood in structure.
Wood Damage
Wood damaged by subterranean termites is often not noticed because the
exterior surface usually must be removed to see the damage. However, galleries
can be detected by tapping the wood every few inches with the handle of a
screwdriver. Damaged wood sounds hollow, and the screwdriver may even break
through into the galleries.
Subterranean termite feeding follows the grain of the wood and only the
soft springwood is attacked (Figure 7 ). Unlike drywood termites or other
wood-boring insects, subterranean termites do not push wood particles or
pellets (fecal material) to the outside, but rather use it in the construction
of their tunnels. This debris, along with sand and soil particles, is used as
a form of plaster.
CREDITS: University of Florida
Figure 7. Wood damage by subterranean termites. Usually damage is with the
grain and is covered with muddy material.
Identification
Subterranean and drywood termites require completely different control
methods; therefore, the termites must be correctly identified. Soldiers,
winged specimens or wings can be identified at your county extension office.
Workers and immatures are virtually impossible to identify. When services of
an experienced pest control operator are needed, contact at least two or three
reputable firms in your area for inspections and estimates for treatment.
Subterranean Termite Prevention and Control
“This is a terrible use of chemicals to poison our soil” D L Jones
The best control of subterranean termites is prevention. The best time to
provide protection against termites is during the planning and construction of
a building. Prevention should include:
* Removal of all stumps, roots, wood, and similar materials from the
building site before construction is begun.
* Removal of all form boards and grade stakes used in construction.
* There should be no contact between the building woodwork and the
soil or fill. Exterior woodwork should be located a minimum of 6 inches above
ground and beams in crawl spaces at least 18 inches above ground to provide
ample space to make future inspections.
* Ventilation openings in foundations should be designed to prevent
dead air pockets and of sufficient size to assure frequent changes of air --
at least 2 sq. ft. to 25 running feet of outside foundation wall. This helps
keep the ground dry and unfavorable for termites.
* Landscape plants and irrigation should not be placed within two feet
of the foundation wall.
* Thorough annual inspections should be conducted to discover evidence
of wood damage or termite activity such as shelter tubes on foundation
surfaces, discarded wings or adult termites.
* Any wood that contacts the soil, such as fence posts, poles and
general foundation structures, should be commercially pressure treated, and
should not be attached to house.
Preconstruction Soil Treatment of Structures
Control subterranean termites by preventing the termite colony in the soil
from entering the structure. It is impossible to build structures so termites
can not cause damage. Therefore, a thorough preconstruction treatment should
be applied to protect the structure for at least 5 years. ouses treated prior
to 1988 with chlorinated hydrocarbons, such as chlordane or heptachlor, should
be protected from termites for 30-40 years.
There are two general categories of termiticides (Table 1 ) that are
differentiated by how termite tunneling is affected when they encounter an
effective soil treatment. The first category is referred to as a, "Repellent
Termiticide." All of the synthetic chemicals classified as "Repellent
Termiticides" are pyrethroids. The name "Repellent Termiticide," is ambiguous;
the chemical properties of the soil treatment only repel termites from the
structure. "Repellent Termiticides" do not kill termites because they are able
to detect the soil treatment. Since the termites are able to detect the
treated soil they do not tunnel into the treated soil barrier.
The other category is referred to as a "Non-Repellent Termiticide."
Termite tunneling is not affected by a "Non-Repellent Termiticide" soil
treatment because the termites are unable to detect the treated soil. Since
they continue to tunnel freely through the treated soil they become exposed to
the "Non Repellent Termiticide" by contact or ingestion and will die. Both
repellent and non-repellent termiticides have proven satisfactory for making
effective barriers when applied properly.
The integrity of the soil treatment is a key factor in providing
protection to the structure. A repellent termiticide properly applied to the
soil will provide protection to the structure unless the barrier is disturbed.
A termiticide barrier composed of a non-repellent termiticide allows more
flexibility and will provide protection even if the integrity of the barrier
is disturbed.
Preconstruction Treatment of Foundation Walls and Piers
After the footings are poured and the foundation walls and/or piers have
been constructed, apply the insecticide to a trench in the soil about 6-12
inches wide and 4-6 inches deep adjacent to the foundation. The insecticide
must be applied to both the inside and outside of the foundation and also
around piers, chimney bases, pipes, conduits and any other structures in
contact with the soil. The trench should be as deep as the top of the footing.
The insecticide should be mixed with water as recommended on the pesticide
label and applied at the rate of 4 gallons per 10 linear feet of trench. The
insecticide should be mixed with the soil as it is being replaced.
Preconstruction Treatment of Concrete Slabs
The most common type of construction in Florida is concrete slab resting
on the soil. Often the slabs crack or shrink away from the foundation wall
allowing termites to infest the wood above.
The soil underneath and around the concrete slab should be treated with
insecticide before the concrete slab is poured. The chemical should be applied
after all the subslab fill and reinforcement rods are in place. Apply diluted
spray to the fill at the rate of 1 gal. per 10 sq. ft. Along both sides of
foundation walls and interior foundation walls and plumbing (critical areas),
apply diluted insecticide at the rate of 4 gal. per 10 linear feet. Treat all
hollow masonry units of foundations with 4 gal. of diluted spray per 10 linear
feet. Apply the insecticide to reach the footing.
Postconstruction Treatment of Structures
Crawl Space Treatment
Dig narrow trenches along both the inside and outside of foundation walls
(Figure 8 ) and around piers and chimney bases, and apply diluted spray as
described above. Also be sure to trench and treat around sewer pipes, conduits
and all other structural members in contact with the soil. Apply the
insecticide to the trenches. The insecticide must be applied to both the
inside and outside of the foundation and also around piers, chimney bases,
pipes, conduits and any other structures in contact with the soil. The trench
should be as deep as the top of the footing. Mix the insecticide with water as
recommended on the pesticide label. Apply the diluted spray at the rate of 4
gal. per 10 linear feet of trench. Mix the insecticide with the soil as it is
being replaced.
CREDITS: University of Florida
Figure 8. Infestation of crawl space construction.
Concrete Slab Construction
It is possible to trench around the outside of a slab after it has been
poured, as described above, but this alone usually will not give satisfactory
control because the termite colony may be entering the structure from the soil
under the slab.
Homeowners are not equipped to treat under slabs after the slab foundation
is completed. A professional pest control operator usually is needed to do
subslab chemical injections ( Figure 9 ).
CREDITS: University of Florida
Figure 9. Treatment of suspended, monolithic and floating concrete slabs.
Termite Baits
Termite baits use small amounts of insecticide to knock out populations of
termites foraging in and around the structure. Some baits may even eradicate
entire termite colonies. Termite baits consist of paper, cardboard, or other
termite food, combined with a slow-acting substance lethal to termites.
Regardless of which bait is used, the customer must be prepared and willing to
accept the possibility of a lengthy baiting process.
Some bait products are inserted below ground out in the yard, whereas
others are installed above ground level on the inside of the structure. Baits
are applied below ground by enticing termites to feed on wooden stakes,
cardboard, or some other cellulose-based material. The toxicant-laced bait can
either be installed initially, or substituted after termites have been
detected in an untreated monitoring device. The more below ground baits
installed, the better the chances of locating termites. Planning, patience,
and persistence are requisites for successfully using below-ground termite
baits.
Termite baits may also be installed above ground in known areas of termite
activity. Typically, the stations are installed directly in the path of active
termite tunnels after the mud tubes have been broken. Effects tend to be more
rapid with above-ground baiting because the procedure does not depend upon
"chance" termite encounters with the stations.
Deciding on Baits or Termiticide Barriers
1. Buildings with hard-to-treat construction or chronic retreatment
histories are logical candidates for termite baits. Some structures have
construction features that interfere with conventional soil treatment methods,
such as wells, cisterns, plenums, drainage systems, and inaccessible crawl
spaces. With baits, gaining access for treatment is seldom a problem since
foraging termites are as likely to encounter below-ground bait stations around
the foundation exterior as well as beneath the structure.
2. Homeowners who do not want floors drilled and furniture/stored
items/carpeting moved are good candidates for baits. Baiting requires fewer
disruptions than does conventional barrier treatment. Installation and
subsequent monitoring of bait stations generally does not even require the
technician to come indoors. Noise, drill dust, and similar disruptions
associated with conventional treatment are avoided.
3. Homeowners who are strongly opposed to the use of pesticides around
their home are good candidates for baits. Although conventional liquid
termiticides pose no significant hazard to humans, pets or the environment
when applied according to label directions, some individuals are still
apprehensive. Chemically-concerned homeowners may find the concept of baiting
more attractive. With baits, the total amount of pesticide applied is small in
comparison to the high gallonages needed to achieve a thorough and effective
soil barrier treatment.
4. Property owners with a serious termite problem or those involved in
a real estate transaction are good candidates for termiticide barriers. They
may not be able to wait 2 to 6 months (sometimes longer) for baits to suppress
or eliminate the infestation.
5. People living in attached housing (condos, attached residences)
where the entire structure cannot be baited are good candidates for
termiticide barriers.
6. In periods of economic instability, soil termiticide treatments may
be preferred over baits. Baits typically require an annual maintenance fee for
the regular inspections. If the fee is not paid, the bait system may be
removed. With soil treatments, at least the termiticide remains in the soil,
regardless of whether or not an annual inspection contract is retained.
Copyright Information
This document is copyrighted by the University of Florida, Institute of
Food and Agricultural Sciences (UF/IFAS) for the people of the State of
Florida. UF/IFAS retains all rights under all conventions, but permits free
reproduction by all agents and offices of the Cooperative Extension Service
and the people of the State of Florida. Permission is granted to others to use
these materials in part or in full for educational purposes, provided that
full credit is given to the UF/IFAS, citing the publication, its source, and
date of publication. 11/29/04
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