THE TERMITE THREAT

Subterranean termites in Queensland

Termites (Isoptera) are an ancient order of insects whose origins date back more than 100 million years to the Cretaceous period. Although they are commonly called 'white ants', the resemblance to ants is superficial and they are more closely related to cockroaches (Blattodea).

Australia has a diverse termite fauna. The order is represented by the families Mastotermitidae, Termopsidae, Kalotermitidae, Rhinotermitidae and Termitidae. The five families include about 30 gener with 258 described, and at least 90 undescribed, species. Termites can be grouped into three categories: dampwood, drywood and subterranean. Dampwood termites generally live in damp rotting logs or rot pockets in dead or living trees. Drywood termites obtain water from the wood in which they live and have no contact with the soil, or with any other source of moisture. Subterranean termites are generally ground-dwelling or require contact with the soil or some constant source of moisture.

Nests

Termites build various types of nest. Some termites have a completely underground existence, apparently without a central nest. Examples include some species of Amitermes . Others build a central nest in the soil, or in dead or living trees. Many economically-important termites build nests of this type, notably Mastotermes darwiniensis and species of Coptotermes and Schedorhinotermes. Still other species, for example in the genera Microcerotermes and Nasutitermes attach their nest to a tree but maintain a soil connection via galleries running down the surface of the trunk. A termite mound is the most familiar form of termite nest. Mounds are often of very distinctive form, and their size and shape vary from hardened flat areas to the tall, columnar structures of  the Spinifex termite Nasutitermes triodiae in North Queensland which may be more than 7m high. Typically, each species builds a characteristic mound, although there may be geographical variation in the size and shape of the mound within species. In the mounds of Coptotermesthe outer wall is hard and built of soil and the inner region is generally composed of woody faecal material (carton) and soil.

Feeding habits and behaviour

Cellulose found in plants, is the basic food requirement of all termites, and all types of plant material can be damaged. Most termite species eat grass and other surface vegetation and have an important role in maintaining soil fertility. They recycle nutrients, in particular nitrogen which is essential for healthy plant growth. When termite mounds erode, the soil particles rich in nutrients such as calcium, magnesium and potassium are washed into the soil from the mound to become available for plant growth. Termite galleries improve soil structure, and assist water entry and storage in soil; surface rainwater runoff and subsequent soil erosion are thereby reduced by the galleries.

Other termite species infest timber and particularly timber which is in an early state of decay by wood rotting fung; Some species of timber are resistant to termites, but none is entirely 'termite proof'. Termites will often damage materials they cannot digest, for example, plastics, rubber, metal or mortar. Primarily, this damage occurs when the indigestible items are encountered during the termites search for food.

Some termites forage for food by means of subterranean galleries or covered runways, which extend from the central nest to food sources above or below ground. The gallery system of a single colony may be used to exploit food sources over as much as one hectare, with individual galleries extending up to 50 m in length for most species.

Distribution and importance

There are about fifteen species of subterranean termite which commonly damage timber-in-service throughout Australia and ten of these occur in Queensland. Our most serious pest species are Coptotermes acinaciformis and the giant northern termite. The former occurs throughout the State while M. darwiniensis is confined to the tropical northern region. Other species which commonly damage timber are Schedorhinotermes actuosus, S. breinli, S. intermedius and S. seclusus and Nasutitermes exitiosus. Coptotermes frenchi and C. lacteus also occur in southern Queensland. The latter constructs mounds usually associated with stumps, and primarily feeds on decayed wood.

Although the coastal belt and northern parts of the state are generally regarded as high hazard areas for subterranean termite infestation, species which damage timber-in-service occur throughout the State. In practice, any structure containing wood is exposed to possible subterranean termite infestation whether in the business heart of a city, in the suburbs or out in the country, unless protective measures are taken.

Source of information

Peters, B.C., King, J. and Wylie, F.R. (1996) Pests of Timber in Queensland. Queensland Forestry Research Institute, Department of Primary Industries, Brisbane.