IPM Action Plan for Subterranean Termites

Pest Management In and Around Structures May 01, 2015 Print Friendly and PDF

 

Identification

Because of their cryptic nature, structural infestations of subterranean termites are usually not visible. Most people become aware of an infestation when annual flights of winged termites (called alates) occur in structures. The alates of Reticulitermes flavipes and Reticulitermes virginicus are dark brown, while those of Reticulitermes hageni are yellowish brown. Alates of Reticulitermes flavipes are generally larger (approximately 0.4” long including wings) than those of Reticulitermes virginicus or Reticulitermes hageni (approximately 0.3” long). Alate wings of Reticulitermes species have two hardened and thickened veins that are visible along the entire front end, but lack the small hairs that are characteristic of the Formosan subterranean termite, Coptotermes formosanus Shiraki. After indoor flights, most alates are found dead near windows or in sinks and bath tubs - usually with their wings still attached.

Soldiers of subterranean termites (Rhinotermitidae) are distinguished from those of drywood or dampwood termites (Kalotermitidae) by their smaller size and the relative width of the pronotum. In subterranean termites, the pronotum (segment immediately behind the head) is narrower than the head, while in drywood termites (Kalotermitidae) they are equally as wide. For termites in the family Rhinotermitidae, Reticulitermes soldiers  are distinguished from those of the Formosan subterranean termite (Coptotermes formosanus Shiraki) by the rectangular-shaped head of the former compared to the oval-shaped head of the latter. In some states, Formosan subterranean termites can be excluded from standard termite control contracts issued by pest control companies. Check with your state regulatory agency for confirmation.

General Information

Reticulitermes flavipes was considered the most common subterranean termite pest of Florida, but our survey indicated that R. virginicus is found almost as frequently in structures as R. flavipes (Scheffrahn et al. 1988). It is less common to find R. hageni infestations. Of the $2.2 billion annually spent for termite control in the United States, subterranean termites account for 80% share, and the majority of this is probably due to R. flavipes and R. virginicus. Subterranean termites follow structural guidelines to gain entry into structures. Structural guidelines include the outside foundations walls, electrical conduits and plumbing lines, and the roots of trees and plants. Subterranean termites form a network of interconnected galleries and feeding sites beneath or above the soil surface. A single colony of subterranean termites, especially those of Reticulitermes flavipes, may contain 100,000 - 1,000,000 termites and forage up to 150 feet in search of food (Su et al. 1993). When subterranean termites search for food above-ground, they may enter a house through small cracks or joints in the foundation, or by constucting shelter tubes along the foundation wall. These tubes are highways connecting the underground termite population with above-ground food sources.

Life History: Flight seasons differ among the three Reticulitermes species and also depends upon where you are located in the United States. R. hageni alate flights begin in early December and last until early February while R. flavipes flights start in early January and end in April. Dispersal flights of R. virginicus occur between early February and late May. Swarming by R. flavipes and R. virginicus occurs during warm, sunny and windless afternoons usually after rain, while R. hageni alates swarm at night. After a brief flight, alates drop to the ground and shed their wings. Females begin to search for potential nesting sites such as moist crevices with wood, and males follow closely behind. The pair forms a royal chamber in a moist site near wood and begin laying eggs, thus starting the life cycle of a subterranean termite colony. Individuals hatched from eggs (called larvae) molt into workers. Some workers may molt into the soldier caste or become alates by molting first into alate nymphs. Some workers or nymphs are capable of becoming supplementary reproductives and take over the role of queen or king if and when a primary reproductive dies or is distanced from part of the colony. It may take five to 10 years for a single pair of alates to form a mature colony that produces alates.

Suggested Thresholds

The threshold for subterranean termites in structures is zero.

Monitoring and Inspection

Evidence of subterranean termites include live or dead termites, shelter (mud) tubes and damage. Because termites consume cellulose, the main structural components of plant cells, any wood material in a house is a potential food source, but they may also damage material that does not contain cellullose. Termites are "cryptobiotic" (i.e., hidden lifestyle), so infestations can be difficult to detect until damage becomes severe. In addition to the presence of alates and shelter tubes, wood material can be probed with a screwdriver or ice pick to locate infested wood. The surface of severely damaged wood may appear to be blistered or peeling, as termites hollow out the wood leaving a paper-thin surface. Reticulitermes tend to cover the wood they feed upon with soil, thus giving wood a more “dirty” appearance than Coptotermes formosanus infested wood. However, it is not advisable to identify the termite species based solely on damage as there are many exceptions.

Outside, you should inspect the foundation of the structure for shelter tubes coming from the soil.  Check any cracks or penetration areas in the foundation where termites might enter.  Pay attention to any areas where the soil line goes above the top of the foundation.  These areas could possibly allow termites to enter the structure undetected.  Look for areas where water may stand next to the foundation due to irrigation systems, water leaks, faulty grade construction or other things.  Inspect any wood to soil contact areas like fences.  Open and inspect any electrical meter boxes set into wall areas.

Inside, inspect and probe carefully door and window facings, baseboards and any hardwood flooring.  Check moisture levels and look for areas were moisture may be present.  Examine any cracks in the foundation or any expansion joints.  Look for blistering paint as it may indicate water damage or termite activity.  Check floor areas for any raised areas.  All plumbing areas should be thoroughly inspected.  It may be necessary to cut access areas in walls for inspection to take place on a regular basis.

Non-chemical Control Measures

Because subterranean termites forage in soil, it is important to keep structural lumber from direct contact with soil. Keeping the lower foundation walls and siding clear of vegetation or mulch makes it easier to inspect for termite shelter tubes. Subterranean termites need moisture for survival. Leaky plumbing, air conditioning condensate, and any portion of a building and its perimeter that collects excessive amounts of moisture should be corrected to maintain an environment less attractive to subterranean termites.

Sanitation/Cultural Control Measures

Eliminate wood to soil contact by removing any fencing abutting the structure or vines climbing on the structure. If water is standing next to the foundation of the building, change the grade of the soil to cause water to drain away from the structure.  In some case french drains may need to be installed to carry water away from the structure. Repair any water leaks inside and outside the building.

Physical/Mechanical Control Measures

Termi-mesh can be installed during building construction. It is a marine-grade stainless steel mesh that creates a physical barrier around the outside foundation wall and slab penetrations. Granitgard is another physical barrier available in Australia. When used as continuous horizontal barriers installed during pre-construction installation, these physical barriers withstood intensive foraging activities of several termite species under field conditions (Su and Scheffrahn 1992, Lenz and Runko 1994). These non-chemical barriers are semi-permanent and can be readily installed during construction. Their physical presence, as opposed to the less visible chemical barriers, also provides ease for verification by regulatory inspectors. 

Biological Control Measures

None.

Chemical Control Measures

Soil termiticides, baits and borate treatments are chemical control measures available for subterranean termite control. Chemical methods of termite control with the anticipated outcome of structural protection should not be attempted by non-pest management professionals.

Liquids

Liquid soil termiticide can be applied during the pre- and post-construction phases.Spraying the soil beneath the foundation with liquid insecticides has been the traditional method for subterranean termite control during the pre-construction phase. The objective is to place a chemical barrier between termites and the structure to be protected. Before the foundation is poured, soil termiticides are applied onto sub-slab soil to form a horizontal barrier. A vertical barrier is applied around the perimeter after the foundation is poured by digging a trench to hold the termiticide.  The trench is then refilled with the soil. Label rates must be strictly followed. There is no allowance for "less than label" (FIFRA 2(ee)) pre-construction applications. Termiticides are commonly referred to as "repellent" or "non-repellent" termiticides. Consult with an experienced pest control operator on the appropriate use.

Baits

Because a subterranean termite colony may contain 100,000 - 1,000,000 termites that forage up 150 ft, the soil termiticide application may not impact the overall colony population. Baits require termites to ingest a toxicant that will usually contain an insect growth regulator that specifically impacts termite development, resulting in the death or significant suppression of the termite colony. Stations are spaced between 10 to 20 feet around structures and require periodic maintenance. Stations must be in the ground in order to be effective; thus, landscape practices that may disrupt station placement should be avoided. Spraying insecticides or other contaminants on or close to stations should also be avoided. Consult with an experienced pest control operator on the appropriate use and maintenance.

Wood treatments

Borates can be applied directly to wood during the construction phase. These products are sprayed onto the wood, resulting in product remaining a slight bit into the wood and on the surface.  Not all states allow borates as a "stand-alone" treatment. Check with your state's regulatory office.

Evaluation Methods

Annual inspections done by a trained and credentialed inspector is the a good investment for property owners as a evaluation method done for termite prevention. Evaluation after a termite treatment for an existing structure includes revisiting the area of infestation and ensuring termite activity has ceased. Depending on the method of control, the time elapsed from the treatment to evaluation inspection will vary.

 

Selected References
Fasulo TR. (2002). Eastern Subterranean Termite and Wood-destroying Insects. Bug Tutorials. University of Florida/IFAS. CD-ROM. SW 158.


Grace J K, Su N-Y. 2001. Evidence supporting the use of termite baiting systems for long-term structural protection. Sociobiology 37: 301-310.


Lenz M, Runko S. 1994. Protection of buildings, other structures and materials in ground contact from attack by subterranean termites (Isoptera) with a physical barrier - a fine mesh of high-grade stainless steel. Sociobiology 24:1-16.


Scheffrahn RH, Mangold JR, Su N-Y. 1988. A survey ofvstructure-infesting termites of peninsular Florida. Florida Entomologist 71: 615-630.


Su N-Y, Scheffrahn RH. 1992. Penetration of sized-particle barriers by field populations of subterranean termites (Isoptera: Rhinotermitidae). Journal of Economic Entomology 85: 2275-2278.


Su N-Y, Ban PM, Scheffrahn, RH. 1993. Foraging population and territories of the eastern subterranean termite (Isoptera: Rhinotermitidae) in southeastern Florida. Environmental Entomology 22: 1113-1117.

 

Credit: Nan-Yao Su, Rudi Scheffrahn, Brian Cabrerra, http://edis.ifas.ufl.edu/in369; Faith M. Oi, University of Florida

 

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