Wood boring insects and beetles are those organisms which are found in and consequently destroy wood. We will discuss some of the more commonly encountered types and in all cases the larva is responsible for the most damage.
The Italian Beetle – Old House Borer
The Italian beetle (Hylotrupes Bajulus) is a European beetle that infests coniferous timber i.e. shrubs and trees that bear cones. It has been recognised in this area since 1935. The Larva of this beetle grows to around 30mm long, is cream coloured and appears to have a swollen front end. A characteristic is three very small simple eyes on either side of the head.
The adult beetle is black with thick grey hairs covering most of the front of the body. There are four spots on each wing cover which may be joined to form light coloured bands and two shiny, raised black dots on the thorax that is between the head and abdomen. This beetles antennae are roughly half the length of the beetle with the female measuring around 17mm and the male 11mm.
The frass is a combination of excreta and wood chewings. The colour of the frass depends on the age and dampness but is often lighter in colour than the wood.
The Italian beetle lays its eggs on and the larvae feed in the wood of coniferous trees. In South Africa these beetles are confined to soft wood trees. The larva bores into the wood for around one to four years in South Africa however, a record of twenty years has been found overseas. This seriously weakens the timber.
The Brown House Borer
The Brown House Borer, ( Oxypleurus nodieri) is a beetle of a uniform gingery brown colour and measures up to 14mm long. The male is usually smaller than the female however the male antennae reaches to around the wingcovers while the female is shorter reaching about two thirds of that length. The egg of this borer is cylindrical and measures around 1.5mm long and 0.8mm in diameter with rounded ends. They emerge usually in winter and are attracted to light. They are active at night.
The larva is a creamy colour with the portion between the head and abdomen being thickened. The head is orange with dark brown wedge shaped mandible clearly visible. They also have very well developed legs with three segments though they are small.
The pupa has antennae, legs and wings as seen in the adult and is creamy white until it is ready to emerge when the eyes, mandibles, legs and wings gradually darken in colour.
Females lay eggs in timber with a high moisture content and the larvae grow slowly over a period of two to six years. During this period the larvae chew and ingest wood in order to create tunnels leaving behind frass.
The frass is in the shape of spiral or twisted shavings.
The Furniture beetle, (Anobium Punctatum), is the most serious which is found widely throughout South Africa. It causes the most damage in coastal areas and is known to attack both hardwoods and softwoods. It varies in length between 2.5 to 5mm long and is a reddish or a yellowish brown.
This beetle can fly well. It has nine longitudinal row of pits on each wing cover.
The female lays her eggs in cracks, joins or rough sawn surfaces, or in old emergence holes. The larva may take two years to fully develop and the adult pushes out the wood dust out in front of it as it emerges.
The fully grown larva is creamy white in colour with a dark head, three pairs of legs and 5-7mm long. Two special characteristics of the Anobium larva is that it remains in a comma shape when removed from its tunnel and does not have an enlarged thorax.
The frass is barrel shaped and feels gritty like salt.
This beetle prefers wood that has been in use for years. The first indication of infestation is the appearance of a hole on the surface of the wood with small piles of sawdust underneath. The galleries created by the larva may be numerous and can seriously compromise the strength of the wood.
The Powder Post Beetle
Powder Post beetles are the most serious threat to hardwoods however they only attack sapwood. There are three types however in South Africa the only important one is Lyctus brunneus. The beetle varies in size but is generally around 4mm long and reddish brown to black in colour. The distinguishing characteristic from the furniture beetle is that the head is clearly visible from above. The last two segments of their antennae are enlarged and appear to be clubbed.
The larvae of the beetle hatch after a week or two depending on temperature and the larval period is spent inside the timber. If wood is severely infested the galleries created may join and the wood could collapse. The fully grown larva will move to just below the surface of the wood and will create a cell in order to pupate that is to become a pupa. Once it emerges from its cell it waits for its body to harden before biting a short tunnel out. Under normal circumstances the this cycle takes a year but if conditions are favourable it could take less than a year however if the wood is cold it could take five to six years.
The frass is very light in colour and resembles face powder.
The Bamboo Borer
The bamboo borer, Dinoderus minutus, is widely distributed throughout KwaZulu Natal and along the east coast. The adult is only about 2.5mm long and can infest cane baskets, furniture, wicker work, bamboo fishing rods etc. they are a reddish brown colour and usually have spikes or protuberances on the front of the body.
The larva is a whitish cream colour with the front end appearing swollen giving it the look of a comma. The head is sunken into the thorax which is the portion between the head and abdomen, and has three sets of poorly developed legs. The larva burrows further into the wood, eating and chewing the timber. The frass is circular and tightly packed behind them.
A lot of these timbers may be protected at the time of felling by chemical processes or painting the end of the timber depending on the wood.
Treatments of woodborer include fumigation, removal and replacement or hypo treatments. For more information on woodborer or a solution suited to your specific needs please contact us for advice on the preferred treatment for you.