Formosan Subterranean Termites

Coptotermes formosanus

Considered one of the most aggressive and economically devastating termite species in the country, the Formosan subterranean termites were introduced to the United States in 1956. These termites are native to Central America and the Far East.

Like other subterranean termites, Formosan termites feed on materials that contain cellulose, but because of their larger colony size, they attack a greater variety of wood at a faster rate than do native subterranean termites. They have an enormous reproductive capacity and a typical colony may exceed 1 million insects.

Although considered "subterranean" (underground, hidden) in habit, the members of the genus Coptotermes regularly construct aerial (above ground) nests within the structures that they infest. The possibility of both a subterranean nest close to the infested structure and an aerial within the structure can greatly increase the damage potential of these termites.

Identification

Formosan termites are considered social insects. Three forms, called castes, are found in the colony - reproductives (winged or wingless), soldiers and workers (pseudergates). Soldiers and winged reproductives (alates) are the castes used for identification purposes.

Workers: Workers of Formosan termites are white to off-white in color and are difficult to distinguish from other termite species. Therefore, soldiers or reproductive caste termites are needed for proper identification. Although ants often swarm at the same time of year as do termites, it is easy to distinguish ants from termites by the shape of their bodies, wings and antennae. They are also referred to as psuedergates

Formosan Soldier

Soldiers: Formosan termite soldiers have tear dropped or egg-shaped, heads compared to the more rectangular head of native subterranean termites. Formosan termite soldiers are more aggressive than native subterranean termite soldiers. When disturbed, they will exude a small amount of a white defensive secretion from a gland called the fontanel, located on the front of the head. They can also attach themselves to a finger with their mandibles (mouthparts). Soldiers will make up between 5-10 percent of a colony.

Formosan Alate

Winged reproductives (swarmers): Winged Formosan termite reproductives or "swarmers" are yellowish-brown and 12-15 mm (0.5-0.6 inch) in length. They swarm at night in late May and early June and are attracted to lights. They have a dense covering of hair on their transparent wings. There are some drywood termites that also have a honey-brown color and are about the same size as Formosan termites. Like the Formosan termites they swarm at night and are attracted to artificial lights. The two species can, however, be distinguished by identifying features such as veins in the wings and characteristics of the head. If identification is in doubt, the termites should be submitted for identification to Center for Urban and Structural Entomology, 2143 TAMU, College Station, TX 77843-2143, (979) 845-5855.

Signs of Infestations

The presence of mud shelter tubes, swarmer termites, shed wings or damaged wood are all signs of an active termite infestation. This evidence may be inside or around a structure.

Swarmers: Swarming reproductive termites on window sills or near indoor lights is the most common sign of an infestation. Formosan termites will swarm at night and are attracted to lights. The presence of Formosan termite swarms indicates that there is a colony nearby and suggests they may be attacking a nearby building or tree. If swarmers are found inside a house it is a strong indication there is an active infestation. They are attracted to windows and will leave wings there that can be used for identification.

Shelter tubes: Shelter tubes constructed of "soil" rise from soil up the side of a foundation and indicate a subterranean termite infestation. When broken open, the active tubes will be filled with termite workers and soldiers.

Damaged Wood: Damaged wood is not often apparent upon initial inspection, but is an indication the current or past presence of termites. Damaged wood can typically be hidden under a coat of paint. When tapped with a hard object, the wood will sound dull or hollow. Formosan termite wood damage resembles wood damage caused by other subterranean termites in that they contain soil deposits.

carton nest

Nests: Formosan termites often form aerial nests made up of chewed wood, soil, saliva and fecal material. These nests can be as large as several cubic feet and found in both the soil and above ground level. They will not be discovered unless the wall coverings are removed. Subterranean nests are typically located away from structures and can be difficult to find.

Formosan Tree Damage

Formosan termites cause the same type of damage as the other subterranean termites. However, they cause this damage more rapidly than native subterranean termites. They have been known to attack more than 47 plant species, including citrus, wild sherry, cherry laurel, sweet gum, cedar, willow, wax myrtle, Chinese elm and white oak. Formosan termites feed on both the spring growth and the summer growth wood. They have also been known to eat through non-cellulose material, such as thin sheets of soft metal (lead or copper), asphalt, plaster, creosote, rubber, and plastic,searching for food and moisture.

Distribution

Texas Formosan Map

The first infestations of Formosan termites in Texas were discovered in 1956 around the Houston Ship Channel in Pasadena, Harris County. Since then, Formosan termites have been detected in 31 counties in Texas, with more being added each year. There have been reports of Formosan termite infestations in all the major metropolitan areas in Texas. It is believed that Formosan termites were transported to the Houston Ship Channel in wooden shoring timbers from the Far East.

(Click on the image for a large version of the map and complete list of counties with confirmed infestations)

 

Formosan Damage

Although there is little chance of encountering Formosan termites outside the upper Gulf Coast region, homeowners and pest management professionals should watch for isolated infestations anywhere in Texas. Shoring timbers and recycled railroad ties are often taken from docks and railways and are then used for the construction of terraces or backyard planting beds. This wood is thought to be the primary mechanism for spreading the Formosan termite in Texas.

Creosote treatment frequently does not reach the core of these timbers and by itself is not guarantee against Formosan termites. These timbers must be properly fumigated to prevent termites from traveling within them and infesting the soil at a landscaping site.