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Biology and Control of the Subterranean Termite
Pest Management Factsheet 98-01
Updated September, 2004
Introduction
A native species of subterranean termite (Reticulitermes spp.), is
present in the dry interior of British Columbia. The same or a related species
is present on Vancouver Island, along the Sunshine Coast north of Vancouver,
and in the the City of Vancouver. These termites perform the important task of
breaking down the large quantities of dead and fallen trees and other sources of cellulose
that continuously accumulate in the forests. Unfortunately they also attack wooden
structures, and if left uncontrolled, will cause weakening and collapse of the structures
due to their feeding activity. Other wood products can also be attacked under the right
conditions. The presence of termites in buildings is cause for concern not only from the
standpoint of safety but also the cost of preventing further structural damage and
replacing damaged wood.
Biology and Description
The subterranean termite is a social insect, living in colonies
that have just a few thousand to sometimes millions of individuals. Each colony will
include reproductives, workers and soldiers. Winged reproductives emerge in a mass nuptial
flight in April and May. These flights are often the first indication homeowners have of
termite infestations. A small emergence may occur in late summer. Reproductives are about
5-6 mm long and are often confused with winged or flying ants because of their
black bodies and transparent wings. The following figures illustrate how to distinguish
between the two types of social insects. The waist of ants is narrow (fig. 1) whereas
termites have a broad waist (fig. 2) between the thorax and abdomen. The antennae of ants
are elbowed (fig. 1) whereas those of termites are straight with bare bead-like
segments(fig. 2). Ants have two pair of transparent wings with few veins and are not of
equal length, and often have a dark patch along the outer margin of the front wing (fig.
3), whereas the wings of termites are about equal in length (8-9 mm) and have many fine
veins (fig. 4).
![](/web/20061229055356im_/http://www.agf.gov.bc.ca/cropprot/images/termite.gif)
Source of figures: Common Ants Pests of Washington: Identification of
Reproductive Forms (Winged). Publ. EB1400, Cooperative Extension Service, Washington State
Univ., Pullman, WA
After flight males and females will break off their wings, form tandem
pairs that have a courtship run on the ground, and then together seek a suitable site to
begin a colony - in wood buried in the ground or laying on the surface of damp ground. The
initial rate of colony growth is slow, however additional egg-laying females are produced
which increase the rate of colony development. Large colonies will subdivide if food
sources are abundant. Winged adults do not appear until the colony is 3 or 4 years old,
then mass emergences will occur each year.
Worker termites are 6 mm long and pale cream in color (worker ants are
yellow, red, brown or black); soldier termites are the same size and color, however their
heads are much enlarged (almost half their body length) with noticeable black jaws.
Soldiers will tap their heads against the wood when disturbed which is another means of
detecting the presence of termites. Workers construct the distinctive shelter tubes and
collect food to feed the young and other members of the colony. Soldier termites are
responsible for guarding the colony and its occupants. Termites continually groom each
other to obtain certain secretions. These secretions help regulate the number of
individuals in the various castes.
Damage
Subterranean termites most commonly live in the soil where they can
avoid temperature extremes and obtain the moisture essential to their existence. Rather
than building a discreet nest like their tropical cousins, subterranean termites construct
numerous scattered nursery areas where reproductives are found together with piles of eggs
and young termites. These nursery areas can be in buried stumps, logs, dead roots or
pieces of lumber left in the backfill after building construction. Nursery areas can also
be found in the wood of structures. These areas can be as far down as 3 to 6 m below
ground level. Because subterranean termites can get moisture from the soil, they can
attack any dry wood or other source of cellulose within foraging distance of the colony.
Besides wood structures, subterranean termites will attack untreated fence posts and
attached boards, utility poles, and any other food sources such as cardboard, paper,
fiberboard in, on, or close to the ground. They prefer to feed on the softer spring growth
of infested wood, leaving the harder summer wood and a paper-thin outer shell of wood.
Termite nursery areas located under sub-floors or concrete slabs near furnaces, water
heaters or other sources of heat can remain active during the winter.
Where a wood source is not in contact with the soil, workers will build
earthen shelter tubes over concrete foundation walls or in cracks in the
concrete through which they can travel to and from the food source and soil moisture.
Occasionally the tubes can be built downward from a wood member to the ground. The tubes
provide protection from predators, especially ants which are mortal enemies of termites.
Besides gaining entry via wood touching or close to the ground, termites
can enter through cracks in concrete foundations and slabs, and through spaces around
utility pipes cut through cement foundations. Workers have been observed following the
roots of spreading junipers under landscape cloth covered with bark mulch or wood chips.
This environment also provides protection from ants and high temperatures. Workers will
also feed on wood chips in contact with soil.
Detecting Infestations
The mass emergence of winged termites in the spring is often the first
sign of an infestation. In the majority of cases, they emerge in homes near sources of
heat - furnaces and water heaters. The appearance of winged termites means that the
infestation has been around for at least 3 or 4 years. Therefore it is likely some damage
has already been done, so it is important to find where the termites have been feeding,
how much damage has been done, and how much repair is needed. A qualified professional
termite control service should be hired to apply an appropriate termiticide to protect the
building from further damage. Other means of detecting infestations include knocking on
walls, floors, sub-floor wood, joists, etc. and listening for the tapping of soldiers, and
looking for shelter tubes on the outside of the building and under the sub-floor. Because
subterranean termites have a constant demand for water, one should closely examine areas
near moist soil, such as below dripping outside faucets, leaking underground sprinkler
pipes and nozzles, and below downspouts.
Where damage or termites are suspected, prod with a sharp narrow
implement to check the soundness of the supporting wood structure. The detection of
termite infestations is best left to professionals who have the experience to do it
thoroughly and accurately. Termites can enter a building from one or more points so it is
important to locate all points of entry for control purposes.
Outdoors, termites can be detected by driving wooden stakes into the
ground at varying distances from buildings and other wooden structures. Examine the stakes
every 3 months for termites or signs of their feeding damage.
Preventing Termite Infestations:
The most effective and least expensive means of protecting buildings
from the subterranean termite is to prevent infestations from developing in the first
place. This includes eliminating existing colonies and potential food sources of colonies
in the vicinity of new construction. New construction should also be pretreated with a
soil termiticide prior to laying of concrete foundations and slabs. The surrounding
grounds should be made less susceptible to infestation from expanding colonies by
eliminating stumps and logs in the vicinity. Termites will readily tunnel through expanded
(EPS) and extruded (XPS) polystyrene. These materials can lead to serious termite problems
when used as exterior cladding below grade and such use is not recommended in areas where
termites are common.
The following precautionary practices will discourage termite
infestations.
- Building sites should be cleared of stumps, roots or other woody material
that remains beneath or adjacent to the building.
- All stakes, forms (including those under concrete steps, cement slabs and
pads) and building debris should be removed from beneath and adjacent to buildings. Do not
backfill over such debris.
- The site should be well drained so that moisture is not retained under,
or adjacent to, a building. Downspouts should carry water away from the building.
- Crawl spaces should be accessible, well ventilated and high enough to
allow working space. Insufficient clearance also makes easy construction of termite
shelter tubes from soil to wood. Make sure air flow through vents is not blocked by
shrubbery or other materials.
- Crawl spaces and basements should be kept clear of lumber, firewood,
sawdust and other woody materials.
- No wood (stair supports, posts or other wood) should project through
concrete floors or foundations.
- Foundations should be of concrete or masonry, and soil debris should be
kept clear of wood resting on them. Make sure foundation wall is high enough to allow
sufficient top soil placement and still leave at least 15-20 cm of clearance between the
bottom of siding or stucco and the ground.
- Slabs, concrete floors and foundation joints should be sealed against
moisture, and regularly inspected for cracks which should be immediately sealed.
- Outside structures such as fences, railings, wooden planters, wooden
sidewalks and stumps or trees should be well separated from houses or other buildings.
Metal flashing can be installed to prevent the passage of termites. Most wood
preservatives will discourage termites.
- Do not stack firewood next to buildings, especially those with wood
siding.
- Avoid placing wood chips or bark mulch adjacent to foundation. Use lava
or other rock instead.
- Avoid over-watering lawns and regularly check for leaks in underground
irrigation systems and dripping faucets. This will also aid in discouraging leatherjacket
(crane fly) infestations in lawns.
Buildings should be checked at least once a year for necessary
maintenance of the above items and unsatisfactory conditions corrected. Surrounding
grounds should be inspected for termites using wooden stakes and remedial action taken to
prevent further spread of termites where detected.
During the construction phase, various methods have been developed to
discourage termite infestations. These include appropriate placement of metal flashing or
shields between cement foundation the wooden structure, ensuring expansion joints are
properly cured and that no spaces exist around utility pipes (sewer, electricity, natural
gas lines) cut through the foundation or slab.
Control products containing inorganic borate can be applied to lumber at
the time of construction or later if exposed to provide life-time protection from
infestation as long as the wood remains dry.
Remedial Control
Control of subterranean termites in buildings can be difficult and
expensive. Chemical (termiticide) treatment is a proven means of protecting buildings from
further damage by subterranean termites. The majority of treatments involve injection of a
termiticide around the entire perimeter of the foundation and under the slab (called a
full treatment) or may only require a partial treatment of the perimeter if the
infestation is very localized. Some termiticides can be sprayed if the infestations are
suited to this type of treatment. Therefore, as previously mentioned, it is important that
a correct diagnosis and thorough inspection be made before any control measures are
implemented.
This is best done through the services of a professional licensed pest control
operator, preferably someone with specialized knowledge and experience in termite control.
Because it takes a long time for termites to cause appreciable damage, there is rarely
need for immediate control action. Therefore building owners should take the time to
contact at least three operators to compare their diagnoses and competitive bids for the
job. Because most homeowners will have never hired a termite control service before, the
question always arises as to how to recognize a reliable service. Get references from
previous customers. Ask about the history of the business, what training the operator has
had in inspecting for and treating termite infestations (not just Pesticide Applicator
training), and if the business or individual belongs to a provincial or national
pest control association.
A reliable operator should provide the owner with a diagram of the
inspected premises, indicating the points of entry and the location and severity
infestations, and an estimate of the control costs along with an explanation of how the
control measures are to be carried out. Be sure to obtain a written guarantee on the
length of protection (usually years) the treatment will provide. Owners with buildings
having hot-water heated basement floors should provide a diagram of the pipe layout if the
floor is to be drilled to inject a termiticide under the slab.
New Methods of Termite Control
New methods of termite control are always being developed by
researchers. Some examples include baits, sand barriers, the fungal pathogen Metarhizium
anisopliae, and transmissible coatings. However none of these techniques are currently
commercially available in Canada.
Termite Links
Prepared by: Hugh Philip, P.Ag.
Extension Entomologist
Food Safety and Quality Branch
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