Termites
Overview
Termites belong to the order Isoptera (Greek meaning equal wing). There are about 2,753 termite species in 285 genera worldwide and less than 50 species in the USA. Termites are known for their unique capability to utilize any cellulose-based materials, such as wood and paper converting them into organic matter. This assists improving soil quality in nature through recycling dead trees or fallen branches and logs. But in human structures, termites feeding habit places them among the most destructive wood-destroying insects, especially in southern sates where these pests are estimated to cause billions of dollars in damage each year.
Identification
Winged adults (called alates) have two pairs of equal length wings. They have filiform to moniliform antennae. They are small to large in size. They have soft body and the waist is not pinched. They have chewing mouthparts. Worker and soldier termites have very small or no eyes at all; winged form has eyes.
Biology
Termites are social insects, they live in colonies that contain eggs, larvae (immatures) and three basic castes: workers, soldiers, and reproductives. Termite eggs hatch into larvae that are capable of developing into any caste, depending on the time of year, diet, and pheromone influences. Reproductives are divided into two categories; primary reproductives and supplementary/secondary reproductives. Depending on the species, termites produce alates (winged sexually matured males and females) at a particular time of the year, that fly at a certain time of the day, and under specific conditions. Alates lose their wings after flying and become dealates (term used of ants, termites, and other insects that shed their wings after a mating flight). Dealates dig into a suitable location in the wood or soil (subterranean termites) next to wood, mate, and start a new colony. Every new colony initially began from the primary reproductives, the king and queen, who periodically mate to support the growth of the colony. Depending on the species, queens can lay thousands of eggs per day and may live for up to 50 years, while the average lifetime of termite's queens is about 15 years. The supplementary/secondary reproductives take the responsibility of laying eggs without swarming when the primary reproductives die, become infertile or removed from the colony.
Habits
Nesting habits
Based on the nesting habits, termites are classified into four different groups:
Subterranean termites: Subterranean termites live in the soil, or in moist wood, but they need soil to survive; therefore, they construct mud tubes to gain access to food, maintain moisture, and protect themselves from predators. Below are common subterranean termite species found in the USA:
- Western subterranean termite - Reticulitermes Hesperus
- Eastern subterranean termite - Reticulitermes flavipes
- Native subterranean termite - Reticulitermes virginicus (Banks)
- Formosan subterranean termite - Coptotermes formosanus
- Desert subterranean termite - Heterotermes aureus
- Arid - Land subterranean termite - Reticulitermes tibialis
Dampwood termites: As their common name may indicate, dampwood termites live in decayed wood with high moisture content, and with most species not requiring contact with the soil. Examples of dampwood termites in the USA:
- Pacific dampwood termite - Zootermopsis angusticollis
- Nevada dampwood termite - Zootermopsis nevadensis
- Florida dampwood termite - Neotermes sp.
- Desert dampwood termite - Paraneotermes simplicicornis
Drywood termites: These termites also do not require contact with the soil. They live in dry wood with low moisture content. Examples of drywood termites in the USA:
- Western drywood termite - Incisitermes minor
- Drywood or Powderpost termites - Cryptotermes sp
- Tropical Rough-headed drywood termites - Cryptotermes brevis
- Tropical Smooth-headed drywood termites - Cryptotermes cavifrons
Mound-building termites: These termites are not known in North America. They usually live in Africa, Australia and South America.
Feeding habits
As above mentioned, termites usually feed on anything that contains cellulose, such as wood, leaf litter, dead grasses, paper, cardboard, carpet, drywall, thin lead sheeting, copper sheeting, plaster, asphalt, flooring, sub-floor, furniture, trim, window frames, etc. They regularly consume about 2-3% of their body weight each day.
Communication habits
- Pheromone communications: Termites use pheromones to recognize the colony mates, as each colony has its own odor. They also use pheromone to locate food sources.
- Sound communications: Termites use special sounds to activate the colony defenses. Solders and workers bang their heads as alarm for defenses.
- Trophallaxis (exchange of food between social insects) communications: Termites transfer food or fluids among members of a community through mouth-to-mouth (stomodeal) or anus-to-mouth (proctodeal) feeding. Trophallaxis helps in:
1.) Recognition of colony mates
2.) Transfer chemicals involved in caste recognition and proportion
3.) Transfer cellulose-digesting protozoa
Foraging habits
Termite workers forage in search for food and water. Depending on the species, food availability as well as environmental factors, such as moisture and temperature, termites foraging distance can vary from short to long areas. For example, Reticulitermes species workers (western, eastern, native and Arid-Land subterranean termites) cover about 0.5 acre, with a foraging distance of 230-260 ft; whereas, Formosan termite workers cover about 1.5 acre, with a foraging distance of 330 ft.
Termite Management
Inspection
Termite inspection is essential to a successful management plan and requires understanding of the building terms, knowledge of species, habits and life cycle, acquiring special tools and items (i.e., flashlight, screwdriver, coverall, bump hat, gloves, measurement tools, etc.), and knowledge of termite's damage.
Treatment
Pre-construction Treatment
In areas known with constant termite activity, pre-construction treatment is effective and time saving way of managing termites. However, the effectiveness of this treatment may be reduced if not enough volumes of termicide were used or if the treated soil was removed or disturbed by construction activities. The goal of the pre-construction treatment is to cover every inch of ground, creating a chemical barrier that keeps termites from moving from the soil to a structure.
Soil treatment with an approved termicide is usually applied before slabs are poured, floors are fitted, foundations are completed, and substructures are erected. The treatment should be applied to entire soil or gravel fill area under slab, around pipes and utility conduits, along all sides of foundations, piers, and interior partition walls.
To provide continues termite barrier, a treatment of soil adjacent to foundation elements is also important after the footings have been poured and the foundation walls and/or pillars have been built.
Post-construction Treatment
Preparation is the key to success. Similar to the inspection, post-construction treatment requires prerequisite knowledge of building construction, termite biology and behaviors, as well as safety application.
Treatment along the foundation "trenching and rodding,"
The objective of trenching and rodding treatments is to create chemical barriers to exclude termites from entering the building. Familiarity with label instructions is a must for success in these treatments, as they provide directions for proper mixing, handling and application practices. For example, the Termidor (a termiticide/insecticide commonly used for termite control in the pest control industry) label says that: "Rodding holes MUST be 12-inches apart. Under some circumstances they can be closer than 12-inches (i.e., clay soil), but the label clearly says that they MUST NOT BE MORE than 12-inches apart. Trenching around the foundation at the rate of 4 gallons finished solution (0.06% or 0.125%) per 10 linear feet per foot of depth, or, if the footing is more than 4 feet below grade, to a depth of 4 feet. Trenches must be a minimum of 6 inches deep or to the bottom of the footing and need not be wider than 6 inches. No treatment below footing should be made".
Sometimes trenching and rodding treatments face a challenge when gaps of untreated soil are present. These gaps will provide perfect reentry points of termites and cause a treatment failure.
Disadvantages of trenching and rodding:
Require plenty of gallons of liquid termicide, which may have some environmental impact.Labor intensive and time consuming requiring drilling many holes around the foundation.Need special tools, such as masonry drills, carbide bits, pumps, large capacity tanks, soil rods, sub-slab injectors, foam machines, etc.
Baiting
There are various termite baits that can be placed in the ground around a structure to attract foraging termites. Due to the trophallaxis behavior, termites share the poison bait with other colony members who will eventually die in a few days.
Advantages of termite baits:
Reduce insecticide usage, which reduce environmental impact.Selective toward termites. This reduces its non-target risks. Management can be achieved without ever entering the home.
Disadvantages of termite baits:
No guarantee that termites will feed on the bait.More costly than conventional chemical treatment.May require up to a year or longer to achieve satisfactory management.
Borate Treatments
Products containing boric acid are commercially available as Tim-Bor ® and Bora-Care® for prevention and control of termites. These products are usually applied directly onto unfinished wood surfaces, and will therefore penetrate into the wood to various depths dependent upon the moisture in the wood and the wood specie. When termites feed on treated wood, they stop feeding and then die. These treatments provide long-lasting protection of termites.
Physical Exclusion
There are various physical exclusion methods as green/non-chemical alternative to chimerical treatments. For example, a study by et al. (1991) size barrier particles of quartz and coral sand in the 1.18-2.80 mm size range effectively prevented Formosan subterranean termite and the eastern subterranean termite penetration and attacks on a structure.
