IPM Action Plan for Formosan Subterranean Termites

Pest Management In and Around Structures May 05, 2017 Print Friendly and PDF

Formosan subterranean termite adults. Photo Credit: Scott Bauer, USDA Agricultural Research Service, Bugwood.org
  • Formosan subterranean termite, Coptotermes formosanus

Identification

Workers are white to off-white in color, wingless and soft-bodied.  It can be difficult to tell Formosan subterranean termites (FST) from other termite species. Alates and soldiers are used for identification (Scheffrahn and Su 1994). Alates, also known as swarmers, of Formosan subterranean termites are yellowish-brown and 12 to 15 mm long (0.5 to 0.6 inch). These termites have four wings of equal size and shape that they can shed after dispersal flights. When viewed with a loop or microscope, the wings have numerous small hairs. Dispersal flights or “swarms” are massive and begin at dusk on calm and humid evenings from April to July. Alates are attracted to lights, so they are usually found near windows, light fixtures, window sills, and spider webs around well lighted areas. Soldiers of FST have an orange-brown, oval to tear-drop shaped head, curved mandibles and a wingless, whitish, soft body. There are more soldiers (10 to 15%) in a FST colony than that of the native subterranean species (1 to 2%).  The tear-drop shaped head is an important characteristic that differentiates FST from other subterranean termite species.

General Information

Formosan termites are social insects with a caste system consisting of workers, soldiers and reproductives.  Each caste has specific tasks for which they are responsible.   Workers are the most numerous within the colony and perform the labor of the colony including locating and collecting food resources, building and repairing galleries and shelter tubes as well as feeding, grooming and caring for all others in the colony (soliders, reproductives and brood. Soldiers are responsible for colony defense. When disturbed, soldiers readily attack approaching objects, and may secrete a white sticky fluid (called defensive secretion) from the fontanel, a gland pore on the top of the head. Reproductives can be either primary reproductives that initially had wings and formed the initial colony after a dispersal flight or supplementary reproductives that form from sexually immature termites within the colony to contribute to egg production within the colony.

The genus Coptotermes contains the largest number of termite pests (28 species) among the >2,800 termite species worldwide, and the Formosan subterranean termite, Coptotermes formosanus, is the most widely distributed and most economically important. The Formosan subterranean termite (FST) acquired its name because it was first described in Taiwan in the early 1900s, but is probably endemic to southern China. This destructive species was apparently transported to Japan prior to the 1600s and to Hawaii in the late 1800s (Su and Tamashiro 1987). By the 1950s, it was reported in South Africa and Sri Lanka. During the 1960s it was found in Texas, Louisiana, and South Carolina. In 1980, the termites were established in Florida. Current distribution of Formosan subterranean termites includes Florida, Alabama, Tennessee, Mississippi, Louisiana, North Carolina, South Carolina, Georgia, Hawaii and California (an isolated infestation in San Diego County), and Texas. A single colony of FST may contain several million termites (versus several hundred thousand termites for native subterranean termite species) that forage up to 300 ft in soil. Because of its population size and foraging range, the presence of FST colonies may pose serious threats to nearby structures.

Life History

A single colony of Coptotermes formosanus may produce over 70,000 alates. After a brief flight, alates shed their wings. Females immediately search for nesting sites with males following closely behind. When the pair find a moist crevice with wooden materials, they form the royal chamber and lay approximately 15 to 30 eggs. Within two to four weeks, young termites hatched from the eggs. The reproductives nurse the first group of young termites until they reach third instar. One to two months after the initial batch of eggs, the queen lays the second batch eggs which will be nursed by termites from the first egg batch. It may take three to five years before a colony reaches a substantial number of termites to cause severe damage and produce alates.  It takes 3-5 years for a colony to become mature  At this point in time a queen can lay up to 2,000 eggs per day.

Formosan termite alates, also known as swarmers. Scott Bauer, USDA Agricultural Research Service, Bugwood.org

As its name indicates, the Formosan subterranean termite is a subterranean termite species characterized by large populations that share interconnected foraging galleries in soil. When these termites invade a house above-ground, foraging or shelter tubes of about 0.25 to 0.5 inch diameter may be found connecting underground colonies and the infested house.  When structures are infested, these termites are capable of creating a "carton nest" made from termite fecal material, wood fragments and soil.  If the above ground colony becomes separated from the underground colony, it can still survive.

Formosan termites will feed on numerous items containing cellulose including structural timbers, paper products and live plants.  this termite is also known to attack non-cellulose materials such as plaster, plastic, asphalt, and thin sheets of soft metal (lead or copper) in search of food and moisture. Their highly publicized ability to penetrate solid concrete is a fallacy. However, the FST is persistent in finding small cracks in concrete which they enlarge and use as foraging routes.

Pest Status
Although their distribution in the United States is more restricted than other subterranean termites such as Reticulitermes species, Coptotermes formosanus can cause substantial economic loss in infested areas. In the city of New Orleans where this termite species was introduced in the 1950’s, the control and repair costs due to FST is estimated at $300 million annually (Suszkiw 1998). It is considered the single most economically important insect pest in the state of Hawaii. As the populations grow, economic loss caused by this termite species in more recently established areas will approach the pest status experienced in New Orleans and Hawaii.

Suggested Thresholds

Treatment is recommended if termites are active within the structure.

Monitoring and Inspection

A single individual of the FST does not consume more wood than a single native subterranean termite, however, because of its large population size, an FST colony can cause more structural damage in a shorter period of time. Wood products that are infested by FST may be recognized by tapping the wood with a hard object to test if it is solid or hollow. In severe infestations, FST hollows out woods leaving a paper-thin surface. A hollowed wood surface may look blistered or peeled . Another characteristic of FST is carton nest material that is made of termite excrement, chewed wood, and soil. Carton nests are usually found in structure voids such as between walls and beneath sinks. The FST generally invades structures from the ground. They commonly enter through expansion joints, cracks and utility conduits in slabs. Any wood-to-ground contact is an inviting entrance for FST infestations. In some occasions, however, FST can form colonies that are not connected to ground, called aerial colonies. If a pair of alates successfully finds suitable conditions, i.e. adequate food and moisture sources in a building, they can initiate a colony with no ground connection. The flat roofs of high rise buildings, because they always pool rain water, are ideal places for the FST to initiate aerial infestations if portals of entry are found.

Non-chemical control measures

Preventive Practice: Avoid wood to soil contact around or near the structure.  If it is necessary, use wood pressure-treated with preservatives (creosote, pentachlorophenol, inorganic salts such as chromated copper arsenate or CCA, etc.).

Sand barriers are uniform sized particles that are installed around structures often about 20 inches wide and 3-6 inches deep.  The particles are so sized so that it is difficult for the termites to tunnel through them.  Sand barriers are easily disrupted around perimeters of structures.

Sanitation/Cultural Control Measures

Break off any shelter tubes found around the structure to see if they are reconstructred to determine if an active infestation is present.  Prune any plants that touch or overhang the structure. 

Physical/Mechanical Control Measures

Repair leaky plumbing, air conditioning condensate are and other portion that may collect excessive amounts of moisture to make the environment less attractive to termites.  Make sure the soil grade flows away from the structure so water does not sit against the foundation.  If drainage problems exists, either change the grade or install drainage systems to carry moisture away.  Make sure that soil does not go above the level of the foundation.

Biological Control Measures

There are nematode species that attack Formosan subterranean termites, but they have not been found to be effective.

Chemical Control Measures

Soil Treatment: Conventional method for control of subterranean termites, including the FST is to place a chemical barrier between termites and the structure to be protected. Currently available termiticides include, permethrin, cypermethrin, bifenthrin, imidachloprid, chlorfenapyr, chlorantraniliprole, and fipronil. Pyrethroids such as permethrin, cypermethrin, and bifenthrin repel termites from treatment barriers, while other termiticides prevent termite invasion by lethal contact. For preconstruction treatment, soil termiticides are applied onto sub-slab soil before the foundation is poured. Post-construction treatment can be done by drilling holes through slabs and injecting insecticides under foundation and by drenching trenches dug in soil along building foundations.

Population Control Using Baits: Because of the large size of a FST colony, application of soil termiticides beneath a structure may not impact the overall population of several million termites that inhabit galleries extending up to 300 ft. In recent years, baits have become available to control FST populations near a structure. One such approach is the monitoring-baiting program that incorporated a bait matrix. Stations containing a monitoring device are first installed in soil surrounding a home. When termites are found in the station, the monitoring device is replaced with a tube containing the termiticide-laced bait. Termites feeding in the stations then carry baits to other members of a colony, leading to the demise of entire colony population.

Evaluation Methods

A thorough inspection can determine whether termite infestations and damage are present, whether control measures are needed and whether there are any conditions that might encourage termite attack (conducive conditions).

Professionals who know the basic construction elements of buildings, the environmental requirements for termite survival and the behavior of this and other subterranean termites are best equipped to perform inspections.

Tools and equipment needed for an inspection may include a flashlight, ice pick or sharp-pointed screwdriver, ladder and protective clothing (bump cap, coverall, rubber knee pads). A clipboard, graph paper and floor plan or sketch help document the findings of the inspection and to ensure that the entire structure has been examined. A moisture meter can detect increased moisture in walls that might indicate conducive conditions, the presence of termite shelter tubes or hidden carton nests. Other termite detection equipment may include fiber optic boroscopes, acoustical detectors, motion detectors, X-ray technology, infra-red cameras and methane detectors. Such equipment can be useful but does not guarantee detection of all termites or their damage to a structure.

Selected References

Grace JK, Tome CHM, Shelton, TG, Oshiro RJ. 1996. Baiting studies and considerations with Coptotermes formosanus (Isoptera: Rhinotermitidae) in Hawaii. Sociobiology 28: 511-520.

Scheffrahn RH, Su N-Y. 1994. Keys to soldier and winged adult termites (Isoptera) of Florida. Fla. Entomol. 77: 460-474. Su N-Y. 2003. Baits as a tool for population control of the Formosan subterranean termite. Sociobiology 41: 177-192.

Su N-Y. Scheffrahn R.H. 1987. Current status of the Formosan subterranean termite in Florida, pp. 27-31. In: M. Tamashiro and N.-Y. Su [eds.], Biology and control of the Formosan subterranean termite. College of Trop. Agr. Human Resources, Univ. of Hawaii, Honolulu, HI.

Su N-Y. Scheffrahn R. H. 1998. A review of subterranean termite control practices and prospects for integrated pest management programs. Integrated Pest Management Reviews 3: 1- 13.

Su N-Y, Tamashiro M. 1987. An overview of the Formosan subterranean termite in the world, pp. 3-15. In: M. Tamashiro and N.-Y. Su [eds.], Biology and control of the Formosan subterranean termite. College of Trop. Agr. Human Resources, Univ. of Hawaii, Honolulu, HI.

Suszkiw J. 1998. The Formosan termite: A formidable foe. Agricultural Research 46: 4-9.

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.