Damage to timber by wood borers is generally minor and rarely needs treating. However, some borers can cause considerable destruction. Knowing the difference can save unnecessary treatment. Most borers are beetles with a four-stage life cycle beginning with eggs, which are laid in the vessels or in cracks in the wood surface. These hatch into the larval or grub stage, which burrow into the wood, producing a network of galleries which may considerably weaken the timber. Adults develop from a pupal stage, burrow out of the wood and fly off to breed. The exit or flight holes of the adult are generally the first signs that borers are present, often with a fine dust (frass) which is borer excrement. When evidence of borers is discovered three questions should be answered:
Is it still active? If not, control measures will be required.
What type of borer was or is responsible? Some are benign.
What is the extent of damage and are structural repairs required? Some of the more important borers found in Australian building timbers are:
This lyctid borer attacks the sapwood of susceptible hardwoods, but not softwoods. The female lays her eggs in the exposed end-pores of freshly cut wood, or in a living tree that has been damaged. Borer attack is confined to about the first five years following felling of the logs, or when the timber moisture drops below 20%. The larvae feed along the grain of the wood and never attack the heartwood, so the damage is superficial.
Attack in plywood that consist of centre veneers of untreated sapwood susceptible to powderpost attack often results in complete separations of the plywood. In the case of structural timbers, the strength of the member might be significantly affected if over 25 per cent of the perimeter were destroyed. Attack of furniture timbers, architraves and flooring is detrimental to their appearance, and therefore no sapwood is to be tolerated.
For property owners and manufacturers, preventative measures are less costly than treatment.
|Scientific name||Lyctus brunneus|
|Description||The adults are up to 7 mm long, dark-brown, shiny, flattened and elongated.Adults have a distinct head and the terminal segments on their antennae appear to be clubbed.
The larvae are cream-coloured with brown head and jaws and three pairs of small jointed legs.
Larvae, on hatching, are about 0.5 mm long and straight-bodied but later become C-shaped.
|Similar species||Lyctus discedens (the small powderpost beetle)Lyctus planicollis
The Malayan powderpost beetle Minthea rugicollis, which was often found in rainforest hardwoods imported from South-East Asia, is now established in Queensland.
|Distribution||Powderpost beetle attack in susceptible timber is very common in tropical and subtropical climates in Queensland.|
|Life cycle||Female beetle lays up to 70 eggs in sapwood containing starch, which is essential for larval growth.Eggs hatch after 14 days and the larvae create tunnels along the wood grain as they feed.
Larvae may take from 2-12 months to mature, depnding on temperature, humidity and food supply.
Fully-grown larvae tunnel towards the surface and create oval cells within which they pupate.
Mature beetles emerge after 2-3 weeks through circular holes (1-2 mm diameter), creating small piles of frass on the timber surface.
rRe-infestation is common for up to five years after tree-felling, until the food resource is depleted.
|Damage||Powderpost (and all lyctine) beetles attack only the sapwood of certain hardwoods and do not attack softwoods.Susceptible timbers must contain enough starch to nourish the developing larvae.
The heartwood is never infested, although adults may emerge through it.
Most infestations occur in logs or sawn timbers drying at the saw-mill.
Infestation may not be noticed until the timber is in-service and adults begin to emerge.
Infested timber contains galleries packed with fine, powdery frass.
The infested area may be reduced to powder within a shell of wood, perforated by emergence holes.
Small piles of smooth, floury frass may be found outside the timber.
Infestation may occur anywhere where susceptible timber has been used (for example, in subfloor areas, living space, roof space, or in furniture and artefacts).
In new houses, emergence holes may appear in the lining materials (for example, in plasterboard and panelling) and joinery. Such holes are made by adults emerging from the hardwood framing beneath.
|Management||Damage is best avoided when sapwood from susceptible timber species is removed by the supplier, or by using non-susceptible timber.Where the damage is not significant structurally, control measures may not be needed except where appearances are important.|
European house borer (Hylotrupes bajulus) is a destructive pest of seasoned coniferous timber including pine, fir and spruce. Damage is caused by the larvae of the beetle. If allowed to become established it can cause major structural damage to buildings. Infestations are most commonly found in roofing timber.
European house borer is known to infest architraves, door frames, roof frames and pine furniture. It only infests seasoned, untreated timber
Emerging adults frequently lay eggs on the same piece of timber. This can continue until no sound wood remains. Wood can be weakened until structures collapse. Larvae of the European house borer are hard to locate and infestations are often only noticed once adults begin to emerge.
|Species name||Hylotrupes bajulus Linnaeus|
|What the borer looks like||Adult beetles are robust and a dark grey-brown to black colour and look slightly flattened. Beetles have two raised shiny lumps on their back, just behind their heads. Adults are about 8-25 mm long with antennae about half that length (see Figure 1).Larvae are rarely seen, as they are hidden in galleries in the wood. They are creamy white in colour with a rippled body and enlarged head. Larvae can grow up to 4 cm in length.|
|What to look for||Frass , a mixture of wood dust and droppings, can sometimes be found on the floor below infested timber where adult beetles have emerged from holesOval shaped holes in timber, typically 5-10 mm in length, running with the grain on the wood surface
Adult beetles, larvae (inside timber) and eggs (laid in cracks and crevices)
A soft scraping sound made by the larvae as they feed. This is most likely heard at night, when it is quiet, and can be audible from some distance.
|Life cycle||Adult European house borer beetles lay eggs in irregularities such as cracks in pine wood. Dead timber on live trees, untreated structural timber and trash can be infested. Damage to timber is caused by the larvae which can take 2-12 years to develop. European house borer is known to infest architraves, door frames, roof frames and pine furniture. It only infests seasoned, untreated timber.|
|Hosts||Exotic Pine (Pinus spp)Douglas Fir (Pseudotsugata spp)|
The common furniture beetle is an introduced pest of exotic pine and some hardwood timbers and is found primarily in imported furniture and occasionally pine timber buildings in Queensland. There are about 1100 species of anobiid beetles (Family Anobiidae) worldwide, but only about 200 of these occur in Australia.
Changes to building practices have decreased the risk of attack to timber-in-service and reports of damage have become less frequent.
Attacks in buildings are generally heaviest in the damper areas including cellars, flooring, skirting boards and outbuildings.
|Scientific name||Anobium punctatum|
|Description||The adult is about 4 mm long and usually chocolate brown with reddish-brown legs.The head is concealed beneath the hooded (cowl-like) prothorax and the antennae end in a three-segmented club.
The beetle is covered with fine yellowish hairs and has longitudinal rows of pits on the forewings.
The adult is larger, more rectangular and not shiny like the Queensland pine beetle; microscopic examination is usually required to distinguish between the two species.
The characteristic shape of the head and prothorax readily distinguish the common furniture beetle from the powderpost beetles, Lyctus species.
The eggs are ovoid and easily seen.
The larva is greyish white with a gold-brown head, chestnut-brown mandibles and is covered with fine hairs.
The larva is normally hook-shaped, but curls into a tight ball when removed from its tunnel.
|Similar species||Queensland pine beetle Calymmaderus incisesPowderpost beetles Lyctus species.|
|Distribution||A small beetle native to Europe where it is a serious pest of timber.Introduced to Australia, it has established in the southern states where it is a pest of exotic pine timbers.
It occurs in cooler, upland areas in south-eastern Queensland (e.g. the Darling Downs) and isn’t considered a pest in warmer regions.
It is found mostly in imported furniture and recorded only rarely from housing timbers.
|Damage to timber||It commonly attacks pine timbers, particularly those which have been in service for at least 20 years.It will attack hardwoods such as English oak and infestations have also been recorded from spotted gum.
Both the sapwood and the heartwood of some timbers can be infested.
Radiata pine in New Zealand is very susceptible and this has led to mandatory immunisation when it is used for building construction or furniture.
In Australia there have been very few examples of attacks on radiata pine, despite the widespread use of this timber – the reason for this anomaly is unclear.
Attacks in buildings are generally heaviest in the damper areas including cellars, flooring, skirting boards and outbuildings.
Life cycle of a wood boring beetle
(Brown rot, dry rot, white rot, soft rot)
All rotting of wood is caused by fungal attack. Fungi are minute organisms which live on and within wood and slowly digest the cell wall materials, leading to softening and decay. All forms of fungal rot – including brown rot, white pocket rot, soft rot, the simply named decay, and the confusingly named wet and dry rots – cause severe damage to timber in service and are often not discovered until the decay is well advanced. Although fungal spores are common in the air, they cannot develop and attack wood unless it has moisture content in excess of about 20% by weight. Dry wood will not rot. Preventing fungal attack is simply a matter of keeping wood relatively dry. This, of course, is easier said than done; some timbers, such as fence posts, are permanently damp and at risk. These should preferably be made from naturally durable timber. The sapwood of most species is not resistant to fungal rot. To repair rotted structural timber, remove the visibly decayed zone together with any surrounding area affected, to be certain of removing all active fungi. Apply fungicides to the remaining timber as a precaution. Recently, a solid form of fungicide based on boron and fluorine has been devised instead of the normal liquid or paste, and has proved effective in treating wooden transmission poles. Inserted as small rods into pre-drilled holes, the fungicide diffuses through the wood only when it becomes wet and fungal attack is likely. Fungicidal rods are suitable for these large-section timbers, but may weaken joints in smaller sections such as window frames.
Cubical brown rot on oak
Brown-rot fungi break down hemicellulose and cellulose. Cellulose is broken down by hydrogen peroxide (H2O2) that is produced during the breakdown of hemicellulose. Because hydrogen peroxide is a small molecule, it can diffuse rapidly through the wood, leading to a decay that is not confined to the direct surroundings of the fungalhyphae. As a result of this type of decay, the wood shrinks, shows a brown discoloration, and cracks into roughly cubical pieces; hence the name brown rot or cubical brown rot.
Brown rot in a dry, crumbly condition is sometimes incorrectly referred to as dry rot in general. The term brown rot replaced the general use of the term dry rot, as wood must be damp to decay, although it may become dry later.
Soft-rot fungi secrete cellulase from their hyphae, an enzyme that breaks down cellulose in the wood.] This leads to the formation of microscopic cavities inside the wood, and sometimes to a discoloration and cracking pattern similar to brown rot. Soft-rot fungi need fixed nitrogen in order to synthesize enzymes, which they obtain either from the wood or from the environment. Examples of soft-rot-causing fungi are Chaetomium, Ceratocystis, andKretzschmaria deusta.
Soft-rot fungi are able to colonise conditions that are too hot, cold or wet for brown or white-rot to inhabit. They can also decompose woods with high levels of compounds that are resistant to biological attack. Bark in woody plants contains a high concentration of tannin, which is difficult for fungi to decompose, and suberin which may act as a microbial barrier. The bark acts as form of protection for the more vulnerable interior of the plant. Soft-rot fungi do not tend to be able to decompose matter as effectively as white-rot fungi: they are less aggressive decomposers
White rots break down lignin and cellulose and commonly cause rotted wood to feel moist, soft, spongy, or stringy and appear white or yellow.
White-rot fungi break down the lignin in wood, leaving the lighter-colored cellulose behind; some of them break down both lignin and cellulose. Because white-rot fungi are able to produce enzymes, such as laccase, needed to break down lignin and other complex organic molecules, they have been investigated for use in mycoremediation applications.
There are many different enzymes that are involved in the decay of wood by white-rot fungi, some of which directly oxidize lignin. The relative abundance of phenylpropane alkyl side chains of lignin characteristically decreases when decayed by white-rot fungi. It has been reported that the oyster mushroom (Pleurotus ostreatus) preferentially decays lignin instead of polysaccharides. This is different from some other white-rot fungi, e.g., Phanerochaete chrysosporium, which shows no selectivity to lignocellulose.
Keep it dry!
Keeping wood in buildings dry will significantly reduce the risk of: swelling and shrinkage cracking fungal rot attack by termites and some borers. Ensure that roof drainage, guttering and stormwater disposal systems are working properly, that there are no plumbing leaks, and that any surface water is drained well away from walls. Underfloor spaces should be kept well ventilated.
The condition of the air in the sub floor area beneath your home has a huge effect on the overall atmosphere within the home. Elevated moisture levels in the air space beneath your home can result in damp sub floor, which can lead to wood decay and rotting floor boards and even rotten bearers. As a result you may find smelly, unhealthy odours invading your living areas.
Poor sub floor circulation can provide the perfect conditions for the growth of mould and fungi, and for termite infestation. Unhealthy air quality in your home can lead to allergies, respiratory conditions, and asthma and lung problems.
By ensuring your home has adequate sub floor ventilation you can protect your health and that of your family from harmful mould and bacterial spores. You can also protect your property from timber damage caused by excess moisture, and from termite attack.
There are various ways to improve the ventilation in subfloor area. Sometimes we improve ventilation by installing vents in the subfloor to create sufficient airflow, in other cases we may need to install fans to create the circulation necessary for a healthy sub floor. We can also offer fans powered by solar panels to reduce your energy costs.
At Redknight our professional team has the experience and the knowledge to identify the problem(s) and provide the best solution for your property.
SUBFLOOR VENTILATION MELBOURNE – UNDER-FLOOR VENTILATION EXPERTS
Our experts at Redknight use moisture meters to measure floor moisture content and work out required air flow to comply with the Building Code Australia.
Keep it coated
Coatings such as paints, varnishes, waxes and oils are the principal means of controlling swelling, as well as protecting and enhancing timbers. Most coatings act as barriers and prevent water penetration into the porous cellular structure of wood. End grain, a cross-section through the original fluid transport system of the wood, is especially vulnerable and requires thorough coating. However, no coatings are totally impermeable to air or water vapour and so moisture can still enter and leave the wood slowly. Small checks or splits in paint coatings are a sign that the wood is swelling and shrinking excessively and that repainting is needed.
Regular maintenance inspections
Wooden items need regular maintenance, and should be inspected every six months. Look in subfloor spaces for signs of rot and termites in the flooring and framing. In roof spaces, look for evidence of leaks that may promote fungal growth. Any sign of breakage or distortion of roof structures should be investigated by a structural engineer. Check external paint finishes for splitting or cracking that may indicate water penetration.
Contact us at Redknight – Experts in Timber borers ,Termite protection, Termite Barriers & Termite inspections in Melbourne, Ballarat and Geelong.