Termites often establish colonies in trees although not always, as they can establish colonies wherever conditions suit. In order to establish a colony they need decayed timber or other organic material, and moisture.
What to do if you find termites in a tree:
Do not cut the tree down. The colony may survive in the ground and be very hard to treat later. It is important to have the termites identified to see if they are a species that can cause structural damage because many do not. Out of the three hundred or so species of termites in Australia, only a handful cause structural damage.
Treatment of the termites will vary depending on species and what is found in the tree. If the termites were only feeding on the tree, methods aimed at indirect colony control would be preferred. If the activity were identified as an actual colony it would allow direct treatment of the nest.
It is best to leave the stump in place on all trees removed. Often trees or their roots may have immature termite colonies with no visible evidence, so the stump can be a great indicator in the future.
If termites are found during the removal of a tree it is preferable to stop the removal until the termites are identified and treated, if appropriate. If it is not safe to leave the tree in place, remove all except the stump so that it can be used as a treatment and monitoring site.
All trees containing termites should be considered unsafe in the long-term because they affect the heartwood of the trunk and often damage the roots. This damage is difficult to measure and even trees with seemingly little damage can suddenly fall because of damage to the roots below the ground. There is no benefit to having a termite-free house if a large tree flattens it. Often the safety of the house and people require that trees be removed as a matter of urgency. We then have to rely on monitors being maintained to detect ongoing activity.
Different species of termites build nests in different ways
Some are single site nesters so all activity emanates from a single colony, whereas others are multi-site nesters that are able to bud off and have several colonies with their own queen, and can operate either independently or connected together. The multi-site situation can make controlling the colony difficult and requires time for all secondary nests to be eliminated.
Some termites build visible nests that can be seen as dome shaped mounds on the ground or up in trees. Around Sydney these are generally the Nasutitermes species of termites. While these termites can gain access to buildings and even cause some damage, they are not nearly as destructive as other termite species. These mounds are also favoured nesting sites for many birds such as the Eastern Kingfisher. Some reptiles such as the Lace Monitor (Goanna) will lay their eggs within the mound, and the Blind Snake can live its entire life within termite galleries, feeding on termites. These small wormlike snakes are rarely seen except during wet periods when they can venture above the ground.
Different termites build nests in different places
The most destructive termite in the Sydney region is the Coptotermes species. In Sydney they can nest almost anywhere. These termites are mostly a single site nester, however they can build secondary nests within buildings that may survive for years isolated from the ground. They love to establish colonies within the root crown of a tree, often with no visible evidence from the outside, but their nests can also be located high up in the trunk of a tree many metres off the ground.
Coptotermes species termite colonies can also survive the removal of the tree and quite often remain completely buried in the ground for decades. Old stone fruit orchards that are re-developed can be particularly bad, with a termite colony left behind where each tree was located. Often the site where a tree has been removed and the stump ground out, is perfect for these termites to form a colony, the winged reproductives can land in the mulch and easily start a new nest.
Coptotermes species will also establish colonies within buildings wherever moisture and hardwood are found. Old buildings with hardwood storey posts or hardwood header beams above windows and doors are particularly vulnerable. These termites are also commonly found in timber retaining walls, fence posts and power poles. Coptotermes species termites are commonly transported from one site to another in hardwood sleepers. Pestforce has been called upon to deal with several infestations that have been transported to New Zealand in hardwood timber sleepers and power poles.
Coptotermes species colonies are also commonly located in voids under concrete slabs. Voids under suspended slabs with timber forming work are particularly favoured, and builders do often forget to remove forming work or leave access to these voids, so they become moist and a perfect place for termites to establish a nest. Because the colony can be directly under a building and contain so many individuals, massive amounts of damage can be caused within a very short time.
The Schedorhinotermes species of termites are also commonly found in trees. Unlike the Coptotermes species they are a multi-site nester, so often when a colony is found it can have multiple satellite colonies that can operate independently if the main nests dies. This species of termite is becoming more common in the Sydney region because of the increased use of mulch in gardens. Schedorhinotermes species can construct a colony anywhere in the ground, they build nests in retaining walls, compost heaps or even timber mulch used in garden beds. Individual colonies can have multiple queens within the nest or nests, and can readily replace the queen should she die, as immature termites can develop into reproductives and take over the job of the king or queen.