Being part of the team of conservators from the National Museum Benin that worked on the stabilization of the Ogiamien Palace (National Monument) sometime in July 2023 was an exciting adventure because we encountered various agents of deterioration, one of which was termites. The termites had invaded the entire structure of the palace thereby weakening the roofs and the walls of the building.
Termites are social insects that live in colonies that may contain hundreds of thousands of individuals. They are dispersed throughout the soil and can extend through underground tunnels known as termite mud tubes to hundreds of feet to reach sites.
Each termite colony contains three forms or castes. The reproductive, the workers, and the soldiers; they are physically distinct and perform different functions. Workers are wingless and the most numerous in the termite colony and they are the castes that eats the wood. They forage for food and water, construct and repair shelter tubes, feed and groom other termites, and care for eggs and the young. The soldiers are wingless and resemble the workers but have a large rectangular yellowish-brown head with a large jaw (mandible). Its function is the defense of the colony.
The reproductive male and female can either be wing or wingless with each capable of producing offspring. The winged reproductive is also known as alate or swarmer, however, they shed their wings soon after flight.
Termites feed on cellulose materials that are readily available in homes and other buildings. They can digest wood because of the protozoa in their gut. The colonies or nests of termites are built in the soil from which they obtain moisture. They feed on wood and other materials containing cellulose (paper, books, cardboard, etc.) and can occasionally severely damage living plants by hollowing out the stem.
The first sign of an infestation is the swarming of the reproductive or the presence of mud tubes on the surface of walls or woods. Other signs include weak or broken structural members, blistered wood and soil in cracks, and distinctive tapping sounds that the soldiers make when disturbed. A homeowner does not discover infestation until a floor or wall collapses.
There are two common species of termites, the pacific dampwood termite (Zootermopsisangusticollis) and the western subterranean termite (Reticulotermeshesperus). A third species called the dry wood termite has been found but is yet to be established. Most termites need moist conditions to become established. For subterranean termites, the moisture source usually is the soil, and damp-wood termite moisture comes from wet wood. Termites are often confused with ants. The termites have straight bead-like antennae while those of the ant are elbowed. The abdomen of the termite is broadly joined to the thorax (no waist), while the ant’s thorax and abdomen are joined by a narrow pedicel (wasp waist). Termite’s wings both the front and hind wings are of equal sizes. The anterior wings of the ant are considerably larger than the posterior wings.
Preventive practices are a critical aspect of termite management. Prevention of termite infestation of wooden structures centers upon disrupting their ability to locate moisture, food (wood), and shelter.
Avoid moisture accumulation near the foundation, which provides water needed for termite survival. Divert water away from the foundation with properly functioning downspouts, gutters, and splash blocks. Soil needs to be graded or sloped away from the foundation for surface water to drain away from the building. Cellulose (wood, mulch, paper, etc.) that is in contact with soil provides termites with ready and unobservable access to food. It is very important to eliminate any contact between the wooden parts of the house foundation and the soil. Maintain at least 6 inches between the soil and porch steps, lattice-work, door or window frames, etc. Never stack or store firewood, lumber, newspapers, or other wood products against the foundation or within the crawl space. Prevent trellises, vines, etc. from touching the house. Before and during construction, never bury wood scraps or waste lumber in the backfill, especially near the building.
Be sure to remove wooden or cellotex form boards, grade stakes, etc. used during construction. Remove old tree stumps and roots around and beneath the building. Avoid or minimize the use of wood mulch next to the foundation.
Termites feed slowly so there is no need to panic if they are discovered in one’s home. A few weeks or months may be needed to decide on a course of treatment, which typically requires employing a professional pest management firm. Homeowners seldom have the experience, availability of pesticides, and equipment needed to perform the job effectively.
Soil barrier termicides
Conventional soil treatments rely on creating a chemical barrier in the soil that is toxic to termites contacting it. Many also have repellent characteristics and termites avoid treated soil. To achieve termite control for long periods, such termiticides must be applied as a continuous barrier in the soil next to and under the foundation. If there are untreated gaps in the soil, termites may circumvent the chemical treatment. Hence, such treatments during preconstruction can provide for more uniform coverage. Once a home is constructed, the chemical has to be injected through drill holes and trenching around the foundation, which can result in less accurate coverage. Effective termite control usually requires specialized equipment and about 150 gallons or more of prepared termiticide solution per house, depending on size, basement, etc.
Termiticides that create a chemical barrier in the soil include bifenthrin, cypermethrin, and permethrin. Chlorpyrifoscan should be used only during preconstruction.
About “spot treatments only” using chemical barrier termiticides only in areas of the house where termites are seen, most pest management firms will refuse such treatments or will not guarantee such treatments. The reason is that termites have a very high probability of finding other untreated points of entry into the structure. Localized spot treatments are considered risky except in re-treatment situations.
Treated zone termicides
The most recent termiticides to be marketed are non-repellent to termites but show delayed toxicity as termites forage through treated soil, which they do not avoid. As termites penetrate the “treated zone,” they contact the active ingredient, which causes delayed mortality and also possibly allows the termites to be overcome by lethal microbes. Furthermore, the toxicant is thought to be passed to nestmates through grooming activities and social food exchange (trophallaxis). Control usually is achieved within three months. As with soil barrier termiticides, specialized application equipment and large volumes of chemical solution are needed.
Non-repellent termiticides include fipronil, imidacloprid, and chlorfenapyr.
Bait technology uses wood or a cellulose matrix favored by termites that are impregnated with a slow-acting toxic chemical. Termite workers feed upon the bait and transfer it by grooming or trophallaxis to other colony members, eventually reducing or eliminating the entire colony. Termites are not site-specific, but rather, they forage among various food sites, which results in the bait being encountered by many colony members. The toxicant necessarily is slow acting because termites tend to avoid sites where sick and dead termites accumulate.
Typically, in-ground stations are inserted in the soil next to the structure and near known or suspected sites of termite activity. Inderground stations often initially contain untreated wood that serves as a monitoring device. The monitoring wood is replaced with the toxicant once termites have been detected feeding on it. In addition, above-ground stations may be installed inside or on the structure in the vicinity of the damaged wood and shelter tubes. Above-ground stations initially contain bait.
Bait systems must be properly installed and diligently serviced. Monthly inspections of a baiting system usually are necessary, except during inclement winter weather. Successful termite baiting requires proper monitoring and maintenance of the stations.
Baits work much more slowly than soil termiticides, and the homeowner should be aware of the possibility of a lengthy baiting process. Several months or more may elapse before the termites locate stations, and then termites must feed on a sufficient amount of the toxicant.
An often-cited advantage of termite baits is that they are “environmentally friendly” because they use very small quantities of chemicals and decrease the potential for environmental contamination. In addition, bait application causes little disruptive noise and disturbance compared to soil treatments. Furthermore, baits can be used in structures with wells or cisterns, sub-slab heating ducts, and other features that may preclude a soil treatment. Baits are often used in sensitive environments.
Several baits to control termites are available in the market. Bait products that are available for licensed pest management professionals include; the Termite Colony Elimination System (hexaflumuron or noviflumuron), Termite Defense System (sulfluramid), Termite Interception and Baiting System (diflubenzur), Termite Bait (hydramethylnon), and Termite Bait Response (diflubenzuron). Not all of these bait systems are effective. It is advisable to review the independent research that has been conducted on particular bait, as some products have been evaluated much more rigorously than others.
Sulfluramid and boratecan be purchased by homeowners. However, Sulfluramid is not recommended as the sole protection against termites; an active infestation should be treated by a professional. Boratecan be used to reduce termite populations. Little or no research has been conducted to verify the effectiveness of these products, particularly when used by homeowners.
Some alternate termite controls
Borates (disodium octaboratetetrahydrate) and pressure treatments (creosote,chromated copper arsenate [CCA]) protect wood against termites and wood-decay fungi. However, even creosote-treated railroad ties and telephone poles, and CCA-treated wood, over time, can be subject to termite attack. Termites can build mud tubes over treated surfaces. Furthermore, they can gain entry through cut and cracked ends or areas where the chemical has not sufficiently penetrated.
Wood treatments are primarily used to supplement other termite control measures because termites can attack untreated wood in other areas of the structure. It is advisable to use pressure-treated wood in situations where wood is in direct contact with soil or exposed to rainfall. Borates are fairly soluble in water, so borate-treated wood should be protected from constant rewetting. Borates may be applied to wood by homeowners.
Physical barriers are particularly appropriate during the preconstruction phase to protect the structure from termites. One such physical barrier is stainless steel-wire mesh (TermiMesh) that is fitted around pipes, posts, or foundations. The newest physical barrier, the Impasse Termite System, contains a liquid termiticide (lambda-cyhalothrin) locked in between two layers of heavy plastic that is installed before the concrete slab is poured. It is supplemented with Impasse Termite Blocker, which uses special fittings around plumbing and electrical pipes and conduits.
Biological control agents
Certain species of parasitic roundworms (nematodes) will infest and kill termites and other soil insects. They have been promoted and marketed by a few companies. Although effective in the laboratory, control is often quite variable under field conditions. Limited success with nematode treatments may be attributed to the ability of termites to recognize and wall-off infected individuals, hence limiting the spread of nematodes throughout the colony. Furthermore, soil moisture and soil type appear to limit the nematodeʼs ability to move in the soil and locate termites.
The fungus Metarhiziumanisopliae (Bio-Blast) is a biological termiticide that requires special application and handling techniques. It is labeled for above-ground application to termite infestation in structures, but it is not labeled for application to the soil. Spray effectiveness is enhanced when applied to many foraging termites because infected termites can pass the fungus to nest mates. However, it is difficult to infect a large enough number of termites for the infection to spread throughout the colony. Furthermore, it provides no long-lasting residual activity, and the fungal spores die with the dead termites. Insufficient research has been conducted to indicate whether this is an effective method for controlling termites.
Breaking up mound and queen removal: Regular disturbance through cracking or breaking of mounds prevents termites from building extensive mounds. Constant digging and plowing of the soil reduces termite activities. Manual destruction of the nest and removal of the queen is also effective.
“Osemeikhian is the Principal Conservator, National Museum Benin.”