Eastern Subterranean Termite

termites_top

Identification

The eastern subterranean termite, Reticulitermes flavipes is the only native termite in New England. It builds nests deep in the soil and feeds on wood buried below or near the soil surface. Symbiotic microbes in the gut of the termite actually digest the cellulose in the wood and then share these nutrients with their host termites. Worker and soldier termites are blind; they avoid light and prefer high humidity often building mud tubes to reach wood above ground. The mud tubes are made of soil and saliva and are about the diameter of a pencil. Large termite swarms occur in the early spring when black, winged reproductive males and females leave the nest in large aggregations to mate and disperse.

Worker termites are small, pale white, soft bodied insects less than .25 inches in length. They make up the bulk of the colony which often number in the hundreds of thousands. Workers bring back digested cellulose nutrients in the form of fecal droplets and share this food with other members of the colony.

termites_worker

Blind white worker with round head and short mandibles.

Soldiers are larger and white bodied with a dark yellow head and long black mandibles. Although much fewer in number they use their large head and mandibles to protect the workers from ants and other predators. Soldiers are unable to feed themselves and depend on the workers for nutrients.

termites_soldier Soldier termite; long yellow head and black mandibles.

Male and Female sexual reproductives are black with four pairs of equal size clear wings. Sometimes the first recognition of a termite infestation comes from seeing large numbers of black winged forms flying inside a building in April. The wings drop off immediately after mating and they may pile up near windows and other sources of light. The clear wings often collect or accumulate in spider webs and this fact confirms termites rather than ants. Once mated, the male (now the King) and the female (now the Queen) stay together for the rest of their lives and together they build a new underground colony that may last for longer than a decade.

termites_queen

Large queen bulging with eggs and smaller king at her side.

Termite damage to wood can be recognized because there are small fecal pellets of digested wood combined with soil particles lining the galleries. Galleries are typically located in wood close to or touching the ground or wood wet with excessive moisture from a leak or other water source. Galleries stay within the limits of the wood as termites avoid increased oxygen and light as soon as they are detected near the wood surface. The result is wood damage that is often not visible unless a metal probe is pushed through the thin wood outer surface.

Biology

Termites can feed on paper, books, buried wood, bark mulch, dead roots and branches of trees and of course wood frame timber in houses. Most damage begins at the foundation level, sill plates and porches are often attacked first. If there is an earthen basement with high humidity, termites can build soil tunnels to reach wood greater than a single story off the ground.

Termites are everywhere throughout New England although sandy soils and certain communities appear to be more heavily infested than others. When termites swarm there is often a mixed flock of birds nearby feeding with frenzy on the protein rich sexuals. Termites normally damage wood slowly over time. There is no need to panic, when an infestation is found, take your time to understand the sources of moisture and the location and amount of damage.

Control

Infestations are often reported because of reproductive swarms coming up inside the building. The dark reproductive winged forms fly in large numbers every spring. Winged termites are often trapped inside a window as they are attracted to light. There may be no damage to the structure, the nest may be in buried wood below the building and the reproductives are entering the building through cracks in the foundation. Sealing these cracks is all that is required to solve this type of infestation. This is especially true when the building foundation is not made of wood.

Traditional control strategies required an insecticide to be applied to the soil as a chemical barrier against termite invasion. This approach used a large quantity of insecticide that was injected under the structure using drills and trenches. However, an advanced technology using termite baits shows great promise. Wood pieces impregnated with a toxicant are set out to survey and control for termite foragers. Termites feed on the bait and return to the nest where they share the toxicant with other nest mates, their young and the king and queen.

I suggest monitoring a building over time to verify that the termite damage in evidence is old and there are no live termites. Removal of the outer section of the mud tubes should reveal live white termite workers if the infestation is active. Likewise, probing into small sections of wood should reveal worker termites. If no active termites are found then it is possible that the termite damage is old. Monitoring for termites can take the form of watching for any live activity during a renovation, reports of swarming termites, and installing wooden monitor stakes around the outside perimeter of the building to detect termite feeding activity.

Stabilizing Damage to Support Beams

There are two boric acid products labeled for wood treatment for the control/remediation of termites and wood boring beetles. Both can be applied by professional pest control operators as a spot treatment to protect and stabilize wood against future and existing attack. Only exposed sections of wood beams can be treated, limiting coverage.

Evaluation of Extent of Damage and Prevention

Careful examination and probing of wood will help determine the extent of the termite infestation and the amount of wood damage. A screwdriver or wood pick can be pushed through termite damaged wood easily. Check around sill plates, under window frames attached decks and porches and any area where wood is in contact with the ground or there is evidence of excess moisture. Conditions that contribute to increased wood moisture should be corrected as part of the renovation. Storm water should be directed away from the foundation and vapor barriers installed over soil crawlspaces whenever possible.

In the past, dogs, especially beagles were trained to detect termites because of the methane gas and odors associated with a colony. Unfortunately there is limited access to crawl spaces and basement sill plates both visually and from an odor detection standpoint. Under most pest control contracts termite control expenses are not refunded, the warranty must be renewed annually and the vendor is only responsible for visible damage. This makes it essential that homeowners read and understand the basics of termite identification, biology and control.

Developed by Gary D. Alpert Ph.D, retired entomologist, Environmental Health & Safety, Harvard University.

Copyright 2013-15 www.pestipm.org. All rights reserved.