Formosan Termites: An Unwanted Asian Invader

Formosan Termites:  An Unwanted Asian Invader
Dr. David J. Holcombe

Formosan termites, Coptotermes formosanus Sharaki, are one of the subterranean termites that now exist in Louisiana.  The indigenous species are smaller, less aggressive and form smaller colonies than their Asian cousins.  In fact, Formosan termites actually came from Southern China, not Formosa (the island of Taiwan), in the 1945 when military materials on palettes of infested wood, were repatriated from the Far East.  These contaminated articles came through one of several naval bases in New Orleans, where the termites found a warm and welcoming climate.


After proliferating for over two decades, they were identified in 1966 after they had firmly established themselves in Orleans and Calcasieu Parishes.  By 2001, they were found in most South Louisiana parishes as well as St. Landry and Sabine Parishes to the north.  By 2008, they were located in Vernon, Concordia, Rapides and Avoyelles Parish in Central Louisiana.  Natchitoches Parish fell victim to their insatiable jaws in 2009.  It is assumed that they are currently located in all 64 Louisiana parishes, but have not been formally identified.


Formosan termites form very large colonies, containing from 500,000 to over 2,000,000 insects.  Each colony contains a king and queen, which can lay over 1,000 eggs a day.  Eggs develop into larval forms which can differentiate into workers, soldiers or alates (winged versions that fly off to mate and establish new colonies where they remove their own wings).


Colonies must have contact with moist soil as a source of water.  Workers, who are constantly foraging for new sources of food in the form of wood or other sources of cellulose, can form burrows that lead from the ground up brick or cement pillars to wood beams above the soil.  Exceptionally, a colony may be established above ground in a location with constantly wet wood, such as rafters under a roof leak, and form an “aerial nest”.


Formosan termites are voracious and aggressive.  Soldiers secrete a poison from their hard, tear-shaped heads, armed with sharp mandibles, that kills their enemies, including gentler native termite species.  Alates (the flying versions) can be seen congregating around light sources at night when they swarm, something that differentiates them from their diurnal native cousins.


Since all termites are attracted to wood, it is advisable to avoid railroad ties and even mulch for landscaping.  Potted plants, shrubs and trees should be kept away from close contact with your home and always leave enough space for proper visibility for regular inspections.  Liquid termiticides exist in either repellant or contact forms.  Contact termiticides need to form a continuous barrier and a gap as small as 1/16th of an inch can provide access to a previously protected zone.  In addition, any disruption of the soil where a contact termiticide has been applied will neutralize the effect by creating gaps.


The choice of control will be a function of construction type, proper application and whether it is for eradication of a current infestation or prevention of future infestations.   Under any circumstances, always avoid wood to soil contact, especially in our moist climate, so perfect for this unwanted “Formosan” invader.