As termite season rolls around, it may be useful to brush-up on your understanding of termite biology. While this may not be the most straightforward topic in the field of pest control, it is one of the most important for those in this line of work.
Subterranean termites occur throughout the temperate and tropical regions of the world, including the continental United States, Puerto Rico, Hawaii and Canada. Most species in the U.S. belong to the genus Reticulitermes. The desert termite, Heterotermes aureus, is found in the Southwestern states and the Formosan termite, Coptotermes formosanus, is found in states along the eastern seaboard and Gulf Coast, as well as Hawaii. It also has been reported in Southern California.
Although the various species have minor differences in biology and habits, the following is a general overview of subterranean termites in North America. Subterranean termites live as colonies below ground, and colonies consist of a primary queen, king, reproductives, workers and soldiers. Workers of the typical eastern subterranean colony generally number up to 250,000, although recent studies indicate that colonies can contain one million or more workers and soldiers. Formosan termite colonies are much larger, with workers usually numbering more than one million.
SWARMING AND NEW COLONIES. Usually once a year, a mature, healthy colony will produce new reproductive termites called, "swarmers." In the warmer months when environmental conditions such as temperature, moisture and light are suitable, the workers construct "swarming castles" (special tubes) and usher the swarmers out for their mating flight.
Termite swarmers are not strong fliers, but can be assisted by wind currents so they reach the tops of buildings. Following a very short flight period, the swarmers come to rest, break off their wings at a special fracture point and attempt to locate a member of the opposite sex. Males follow females in an attempt to mate.
Swarmers emerging indoors usually die within a few hours and are seldom successful in starting new colonies. An exception exists if sufficient moisture is found inside the structure. The Formosan termite is more successful than other species at entering and surviving in structures. PCOs along the Gulf Coast believe that as many as 40% of infestations in buildings occur through termite entry into roof structures.
A male (king) and female (queen) which find a suitable nest area usually a ground contact beneath a rock or wood create a chamber and the queen begins laying eggs. During the first season only a few dozen eggs are produced. Later, when workers have enlarged the chamber and collected cellulose for food, the queen's egg production increases. The workers carry out all other functions.
Within four or five years the colony is usually large enough for new swarmers to be produced and the cycle repeats itself. Although the scientific community is not sure exactly how long a queen lives, it is believed that a queen can live and reproduce for up to 25 years. The king may die more quickly, but it is believed the queen can continue to produce viable eggs even in the absence of the king.
If the original queen is eliminated, or when larger colonies find new food sources that are somewhat remote from the primary colony, healthy colonies can form secondary reproductives. The reproductive organs of certain workers (which are females) mature and these secondary reproductives can produce viable eggs to sustain the colony. Secondary reproduction can also occur if large numbers of workers are cut off from the colony (as through a chemical barrier) and there is suitable moisture to support a new "satellite" colony, or a colony bud. Formosan termites commonly produce satellite colonies, which in turn may produce secondary reproductives. The satellite colony eventually becomes independent of the original parent colony.
For Reticulitermes, large colonies may also produce secondary queens at swarm, which may emerge with swarmers and start new colonies. However, swarming may not occur every year if environmental conditions are not suitable. Swarmers produced but which do not swarm within a certain period of time are probably cannibalized by workers in the colony.
A swarm indicates a mature colony which is at least four or five years old. However, swarms inside a building do not indicate the termites have been in the building for that long. The colony might have discovered the building only during that season.
Post-treatment swarms can also occur. It is not uncommon for a colony to pro-duce swarmers shortly after a soil treatment with a termiticide. If this occurs, it usually happens within a few weeks (and perhaps within two months) of the application. This response may be due to the increase in moisture from the water in the termiticide solution or it may be in response to the chemical barrier as swarmers trapped in the building make a last-ditch effort to escape. Post-treatment swarms are usually a positive sign that the chemical barrier is effective. However, swarms occurring more than two months after treatment usually indicates the treatment needs to be evaluated.
FOOD AND FORAGING. Termites feed on cellulose materials with wood being the most common source. They are also known to sometimes damage non-cellulose materials. Examples are pin holes in plastic food liners (termites are attracted to water condensed on the liner base) and plastic coatings on electric cables.
Native subterranean termites can forage as far as 250 feet from the colony in the soil. Formosans can forage for a distance of 500 feet from the colony. Normally workers do not expose themselves to light. If foragers must cross substrates such as concrete, they build tubes between the soil and the food source above to protect themselves from exposure to light and dry air. If tubes are broken, termites quickly repair them if they're being used. Broken, unrepaired tubes indicate the termites are not actively using those tubes.
Although tubes are usually built up from the soil, if foraging termites are some distance from their usual soil contact (such as in the middle of a beam in a crawl space) they will build tubes down in an attempt to reach the soil by a more direct route. Tubes coming down a foundation wall often indicate a good chemical barrier in the soil and that the termites trapped above are exploring other avenues to reach the soil.
Foraging termites consume cellulose material and either take it back to the colony or pass it along to other workers who transport it back. A long standing myth is that termites go back to the soil every 24 hours, but this has not been substantiated. In fact, observations suggest that some workers may remain in the wood above grade for several days at a time, especially Formosans that live in carton nests.
The exchanging of food among termites, or "trophallaxis," permits the soldiers (which can't feed themselves), young workers, and the king and queen to re-ceive food. It also permits pheromones to be passed among the colony members. Pheromones regulate many activities in the colony, including the ratio of workers to soldiers, suppression of secondary reproductives and production of swarmers.
Native species in a colony consisting of 250,000 workers can consume approximately 1 cubic foot of wood per year. This is equivalent to 20 linear feet of a 2x4. This rate is predicated on a colony of this size, that this is the only food source for the colony, and the colony is active 12 months of the year. Under normal conditions especially in the Northern states less wood is consumed during a year as feeding slows during the winter. The colony may also be feeding on old tree stumps and other natural sources outside the building.
Larger native colonies can cause damage at a greater rate. Formosan termites, because of larger colony and worker size, can cause even greater damage in a year's time. However, even at the higher rates of feeding, little damage occurs between the time of first discovering the termites and a treatment which might not take place for several weeks.
MOISTURE REQUIREMENTS. Subterranean termites require contact with a moisture source. The soil is the normal moisture bank. Wood in which termites are working often contains up to 21% moisture in the galleries. Normal, dry wood in structures usually contains only 8% to 12% moisture. Termites bring wet mud into the wood galleries to regulate the moisture in their environments.
When a termiticide is used to create a chemical barrier in the soil, termites in the structure die either from lack of moisture or when contacting or crossing the chemical barrier to reach the colony in the soil. Subterranean termites trapped above grade following an application of a soil termiticide can live from two weeks to two months after treatment. If there is excessive moisture in the structure, this time is prolonged. If there is sufficient moisture and enough workers trapped above grade, a secondary or satellite colony can be produced. This is why above-grade moisture sources need to be located during inspections and corrected in conjunction with treatment. Significant moisture problems can permit the termite infestation to continue even if the chemical barrier is perfect.
How much is "sufficient moisture?" Termites must find free-standing water such as condensation, rain or plumbing leaks. If standing water is not available, the wood must be saturated; that is, it must contain at least 30% moisture. However, Formosan termites can build carton nests in wall voids with a secreted, glue-like material. This material seals moisture in the nests, allowing prolonged survival away from soil. Fumigation of the structure or direct injection of chemical into the nest is often necessary to eliminate the above-grade portion of Formosan colonies. Otherwise, the termite infestation may not be eliminated.
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TERMITE TRIVIA * Most species in the United States belong to the genus Reticulitermes. The desert termite, Heterotermes aureus, is found in the Southwestern states and the Formosan termite, Coptotermes formosanus, is found in states along the eastern seaboard and Gulf Coast, as well as Hawaii.* Workers of the typical eastern subterranean colony generally number up to 250,000, although recent studies in Florida and Toronto, Canada, indicate that colonies can contain one million or more workers.* Most species swarm in the late morning hours, but Formosan termites usually swarm in the early evening.* When conditions are less than suitable, an individual colony may swarm several times over several weeks, releasing only a portion of the swarmers each time.* The Formosan termite is more successful than other species at entering and surviving in structures.* Within four or five years the colony is usually large enough for new swarmers to be produced and the cycle repeats itself.* Secondary reproduction can also occur if large numbers of workers are cut off from the colony (as through a chemical barrier) and there is suitable moisture to support a new "satellite" colony.* Post-treatment swarms can also occur, and are usually a positive sign that the chemical barrier is effective.* Termites feed on cellulose materials with wood being the most common source.* Native subterranean termites can forage as far as 250 feet from the colony in the soil. Formosans can forage for a distance of 500 feet from the colony.* Tubes coming down a foundation wall often indicate a good chemical barrier in the soil and that the termites trapped above are exploring other avenues to reach the soil.* Foraging termites consume cellulose material and either take it back to the colony or pass it along to other workers who transport it back.* Pheromones regulate many activities in the colony, including the ratio of workers to soldiers, suppression of secondary reproductives and production of swarmers.* Native species in a colony consisting of 250,000 workers can consume approximately 1 cubic foot of wood per year.* Subterranean termites require contact with a moisture source.* Termites bring wet mud into the wood galleries to regulate the moisture in their environments.* Subterranean termites trapped above grade following an application of a soil termiticide can live from two weeks to two months after treatment.* Significant moisture problems can permit the termite infestation to continue even if the chemical barrier is perfect.* Formosan termites can build carton nests in wall voids with a secreted, glue-like material. |
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PREMISE EUP TRIALS PROVE SUCCESSFUL Premise Insecticide from Bayer Corporation performed successfully in all Experimental Use Permit trials, the company reported. Complete protection from termites has been reported in all 131 sites treated with Premise. Bayer was granted a three-year EUP by the U.S. Environmental Protection Agency in 1993. The permit allowed the company to set up trials in up to 90 termite-infested homes per year in 24 states from March 1993 to March 1996. Of the 131 homes that were treated during the three-year period, 122 were treated with label rates of Premise ranging from 0.05% to 0.1%. The other nine homes were treated with a lower concentration rate. Premise was applied by professional pest control operators on homes and businesses with active termite infestations. Under the guidelines of the EUP, PCOs and Bayer representatives were to apply Premise, inspect 30 days after treatment, and inspect again annually for three years. Sites initially treated in 1994 and 1995 are still being re-inspected. At press time, 106 of the 131 sites had been evaluated. According to Bayer officials, structural protection is being maintained at all 106 sites. "We are very pleased with the results we've seen from the EUP trials," said Mike Ruizzo, pest control research product manager for Bayer. "These trials show Premise works in the real world." The PCOs and Bayer personnel performing the treatments chose the houses they would treat in order to test a wide range of soil types, pH levels and construction types. Premise was also used against a variety of termite genera around the country, including Coptotermes, Heterotermes and Reticulitermes.
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