IPM Manual for Structural Pests in British Columbia
Chapter 9: Termites
When you have completed this lesson, you should be able to:
- Describe Western subterranean and Pacific dampwood termites and their typical nests.
- Describe subterranean termite damage.
- Describe an inspection and monitoring program for subterranean termites.
- List conditions that favour termite survival and how to remedy them.
- Describe the properties and use of solid borates and soluble borates in termite control.
The Western subterranean termite occurs mainly on Vancouver Island and in the Kamloops and Okanagan areas of the province. It can cause extensive damage to wood in buildings and is the species of termite that causes the most serious problems in British Columbia. Another species, the Pacific dampwood termite damages damp, decaying wood, but does not damage sound wood. It occurs in the lower mainland, on Vancouver Island and north along the coast to Prince Rupert and the Queen Charlotte Islands.
Termites are social insects that live in large colonies, with at least one queen. There is often a king termite as well that mates with the queen. Besides the royal pair and their developing offspring or nymphs, a termite nest also contains worker and soldier termites. The workers care for the larvae and forage for food; they are pale, cream-coloured and wingless. The soldier termites defend the nest; they have greatly enlarged, brownish heads and mouthparts. Periodically, usually in the fall, large swarms of winged termites leave the nest to mate and start new colonies.
Termites eat wood, which is digested for them by protozoa (microscopic, one-celled organisms) living in their gut.
Western Subterranean Termites (Reticulitermes hesperus)
The workers and soldiers of this species are 6 mm long. The winged forms are larger, 13 mm long.
Subterranean termites must maintain regular contact with a supply of moisture, which usually means they must stay in the soil. They can live in sound wood above the soil, but only if there is a constant supply of moisture available to them. To keep this contact with moisture, these termites sometimes build characteristic mud tubes to allow them to bridge the distance between the soil and susceptible wood. They also pack a cement-like mixture of chewed wood and soil into the galleries they excavate in wood; when this is seen, it is an indicator of a subterranean termite infestation.
Subterranean termites can attack any damp or dry wood, including hardwoods and softwoods. Although the first damage begins at the wood surface, termites can go on to excavate galleries throughout the wood. These tunnels or galleries may penetrate deeply into larger timbers.
Pacific Dampwood Termites (a Zootermopsis species)
This species is one of the largest termites.
The workers and soldiers are 20 mm long, while the winged forms are 25 mm long. They must live in moist conditions, therefore they are only found in damp and decaying wood in contact with the soil. Dampwood termites leave large, oval fecal pellet (droppings) in the nest. This distinguishes them from subterranean termites, which do not leave pellets in the nest.
A thorough visual inspection is currently the main monitoring technique for finding termite infestations. Finding mud tubes or tunnels from the soil to wood is an obvious sign of subterranean termites. Other signs are damp or damaged wood with holes or tunnels in the wood and wood that sounds hollow or soft when tapped. During an inspection, a screwdriver or ice pick can be used as a probe to pry into suspect areas and open up holes enough to see whether termites are present.
Inspections also include looking for conditions that promote wood decay or that could allow termites access to wood close to the soil. Examples of things to look for are:
- Wood in contact with soil, such as posts in soil or set in concrete (they may go through to the soil), porch steps that rest on the ground, wood form boards left after foundations are poured, woodpiles and other wood debris around the house.
- Damp or poorly ventilated areas, such as around shrubbery near air vents, leaking pipes or faucets, garden planters built next to houses, low foundation walls or footings where wood siding is close to the ground.
- Cracks in foundations and concrete slabs that allow subterranean termites access to wood.
For Western subterranean termites, it is also important to inspect warm areas near ground level, such as around and under a furnace, hot water tank, freezer or electric heaters.
Future Monitoring Tools for Termites
Several new methods for termite detection are being tested in the U.S. These may be of use in future for subterranean termites:
- The Sentricon® system of termite bait stations, registered in the U.S., which can be used as a monitoring device as well as a control.
- An electronic odour detector that works by detecting the gases that termites emit. Although it is currently being marketed, its effectiveness has not been fully studied.
- A hand-held, portable acoustic-emission detector that can detect the feeding of a single termite. The detection range is several feet. This would probably be most useful for monitoring the effectiveness of treatments.
- A fibre-optic scope to allow viewing of areas behind drywall and paneling. It helps the pest control operator to pinpoint infestations so that treatments can be localized.
- Specially trained dogs to sniff out termites (e.g., Tadd Dogs®) are available in the United States. A properly trained dog and handler team can accurately detect termite galleries that might otherwise be overlooked.
The presence of termites in a structure means that action should be taken. If only damaged wood is found, but no live termite are seen, further detailed inspections should be made to determine whether an active infestations is still present.
All termite control programs must remedy the conditions that make the environment favourable for termite survival. Examples of prevention measures include:
- reducing the moisture level in wood
- eliminating direct contact between wood and soil
- ensuring there is at least 15 cm between the soil surface and the bottom edge of wooden siding.
- removing tree stumps and wood scraps from near the house
- filling cracks in foundations to prevent termites from reaching wood, and
- using treated wood where contact with soil is unavoidable
Borates: Both soluble borates (Tim-bor®) and rigid borate rods (Impel® rods), are registered for subterranean termite control.
Impel rods are solid fused borate cylinders. They are nontoxic to mammals and are easy to use. Holes are drilled into susceptible wood and the borate rod is dropped into the hole. The hole is then closed with a nylon plug. If the wood gets wet, the borate rod slowly dissolves and spreads through the wood by diffusion. This provides permanent protection against termite infestations.
Tim-Bor is registered for use on structural wood to control termites and other wood-destroying insects. The borates can be mixed in a water solution and applied to wood, sprayed on as a foam or injected into wood. The time it takes to eliminate an active termite infestation depends on the lumber thickness, size of the termite population, moisture content of the wood and thoroughness of the application.
Sulfluramid: A promising method of termite control involves live trapping termites, treating them with the slow-acting poison, sulfluramid, and then returning them to their nest. The poisoned termites are groomed by others and the poison is gradually spread throughout the colony.
Hexaflumuron: Hexaflumuron is an insect growth regulator (it is a chitin inhibitor) currently being developed as a bait for termite control. It is slow-acting, which allows it to be spread throughout the colony in normal feeding activity.
Methoprene: This insect growth regulator (a juvenile hormone) is currently registered for fleas, but not for termites in Canada. It shows promise for disrupting development of termite nymphs.
Bio-Blast® is the brand name of a product containing a strain of fungus that infects termites. It is applied into active termite galleries where it contacts termites. As other termites groom the infected termites, the fungal disease is spread throughout the colony.
At present chlorphyriphos (Dursban TC®) is the only insecticide besides the borates (above), registered for subterranean termite control in Canada. Part of the Dursban TC label lists the steps that the pest manager should take to remedy conditions leading to abnormally high moisture conditions and to repair and remove water damaged wood.
Visual inspections should be made after treatments to evaluate the success of the treatment program.
Bennett, G., J. M. Owens, R. M. Corrigan. 1988. Truman's Scientific Guide to Pest Control Operations. 4th ed. Purdue University/Edgell Communications. 495 pp.
Mallis, A. 1990. Handbook of Pest Control. 7th ed. Franzak and Foster, Cleveland, OH. 1,152 pp.
Marer, P. J. 1995. Residential, Industrial, and Institutional Pest Control. University of California Statewide IPM Project. Pub. 3334. Oakland, CA. 213 pp.
Olkowski, W., S. Daar and H. Olkowski. 1991. Common-Sense Pest Control. The Taunton Press, Newtown, CT. 715 pp.
Quarles, W. 1995. Least-Toxic Termite Baits. Common Sense Pest Control Quarterly. XI(2):5-17.
|Study Questions - Chapter 9 Answers are given here.
|1. Answer true or false for the following:
|___ Dampwood termites can live in wood that is not in contact with soil.
|___ Subterranean termites must be in regular contact with moisture.
|___ Subterranean termites build mud tubes to bridge the distance between soil and susceptible wood.
|___ Termite galleries are found only on the surface of wood.
|___ In B.C., subterranean termites are restricted to Vancouver Island.
|2. What are three signs that subterranean termites may be present?
|3. List three examples of what to look for during an inspection for conditions that favour termite infestations.
|4. What preventative measures remedy the conditions that make the environment favourable for termites?
|5. What is the primary control for Pacific dampwood termites?