Drywood Termites

Brief:

Drywood termites obtain water from the wood in which they live and do not have contact with soil. The native species live in dead branches, branch stubs, fire scars and logs of a variety of host trees. Attack is mainly restricted to the sapwood, but galleries may extend into outer layers of sound heartwood. Infestations are often indicated by the presence of dry, sand-like faecal pellets (frass) expelled from openings in the gallery systems.

Habits

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; the galleries thereby reduce surface rainwater runoff and subsequent soil erosion.

Other termite species infest timber and particularly timber, which is in an early state of decay by wood rotting fungi. 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. In the case of the giant northern termite, individual galleries may extend as far as 100–200 m. Apart from grass-eating species, which forage in the open all termites remain within a closed system of galleries, devoid of light. The only exceptions are during a swarming flight, or when repair or new construction is occurring. The advantages to the termites of this closed system are twofold. They are protected from natural enemies such as ants, and they gain a measure of protection from temperature and humidity extremes. Termites have a thin external covering and have relatively little resistance to drying out.

Habitat

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 northern Australia, which may be more than 7 m 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 Coptotermes the outer wall is hard and built of soil and the inner region is generally composed of woody faecal material (carton) and soil.

Threats

Although the coastal belt and northern parts of the country are generally regarded as high hazard areas for subterranean termite infestation, species that damage timber-in-service occur throughout mainland Australia. 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.

Prevention

Others

Photos and information are provide by Scott Kleinschmidt - BASF.

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