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  • Writer's pictureBenny Kuriakose

Insect Attack on Timber and Its Prevention

Timber is prone to a lot of wood attacking insects, apart from termites. Wood boring insects or wood borers are some that can cause extensive damage to timber as well as other wooden structures. These arthropods feature a range of species at various stages of their lives- from larvae to adults. Wood boring insects are seen as a menace in urban and rural settings. The damage caused by them is enormous and irreversible. The insect damage on timber and its infestation in homes and furniture go unnoticed and it might be too late when you notice them.

Dry timber is at less risk of insect infestation than moist timber. Like the dry rot and wet rot in timber, some wood boring insects aid in decomposing dead trees while some damage crops and cultivation. One should see to it that the timber used in construction or as furniture is properly cured and treated against such attacks. Thus, this article aims in helping you to know more about the pest attacks on timber, and the treatment that is required to fix them.

The wood beetle damage on timber is something that can not be fixed if it goes unnoticed. There are a variety of these wood beetles. Here are some of the wood boring beetles that cause damage to timber:

  • Deathwatch beetle

  • Common furniture beetle

  • False powderpost beetles

  • Powderpost beetles

  • Old house borer

  • Anoplophera longhorn beetles

  • Wharf Borer

List of Contents

1. Wood Borers

Wood borers attack timber and leave a disfigurement on its surface, in the shape of small circular or oval holes. They cause a gradual reduction in strength; sometimes to the point of complete destruction of the sapwood. Borers prefer to burrow along the grains and consumes the softer, less dense timber. The moist wood is also easier to digest.

There are some insects which only attack green and unseasoned timber. Their attacks will produce holes that will be present in the timber even after seasoning (drying) the wood. These holes should be inspected carefully to ensure that they are not fresh and that there is no leftover bore dust.

On inspection of such infestation, the size of these holes must be measured. The presence of any bore dust in close proximity to the timber in context must be verified along with its appearance. Apart from termites and the fungal decay in timber, wood borers are the next threat to timber. Different types of wood borer treatments can be tried.

2. Different Types of Wood Borers

In India, there are many types of wood borers. Some of them are beetles with a four-stage life cycle beginning with eggs, which are laid on the surface of the timber or in cracks present inside the timber surface. Within a few weeks, the larvae hatch out and then burrow into the timber, feeding on it and growing in the process. The tunnels which are made by the larvae are filled with bore dust and some of this may appear on the surface.

One of the deadliest ones is the wood borers which normally attack softwood. During favourable conditions, when the timber is moist, they attack hardwood too. The exit hole which is made by this type of borer is 10 to 15 mm in diameter.

The hole made by the furniture beetle is very small and timber is structurally weakened only if a great number of these holes tunnelled by a large number of grubs are developed over many years. Exit holes of 1 to 2 mm diameters produce fine bore dust. Their excreta pellets are ellipsoidal in shape. They infest a wide range of timbers but normally attack sapwood more than others.

The grubs of the deathwatch beetle thrive particularly well on very old timbers that have suffered decay, and they rarely attack softwood. The exit holes are circular, with an average diameter of 3mm. They produce coarse bore dust. Their excreta pellets are bun-shaped.

3. How to Identify the Attack by the Wood Borers?

Timber rafters which had been badly attacked by beetles. The holes are of different diameters and shapes.
Timber rafters which had been badly attacked by beetles. The holes are of different diameters and shapes.

The presence of fresh, brightly coloured bore dust along with clean dust-free flight holes are a clear indication that the borers are still active. Their absence may not necessarily mean that the attack has stopped. The structural integrity of the timber is something that should be checked and not compromised. The number of flight holes may not be related to the extent of the attack. It is possible that the before remedial treatment that was unsuccessful has discouraged the flight holes to be visible to the eye. But it could also mean that the attack was allowed to continue within the timber.

4. How Should the Timber Be Treated When the Borers Are Found?

Spraying of the chemicals will only penetrate a few millimetres into the heartwood (the dense inner part of a tree trunk). It is sufficient to kill most of the insects, but the beetles may tend to avoid the treated areas. Natural predators such as spiders may also get killed by the spraying of chemicals. If the timber surface is painted or varnished, the chemicals will not go in.

The method of application by drilling holes in the timber cannot be used for exposed and sensitive timber members. Pressure injection is another method of injecting chemicals by drilling 10 mm holes in the timber surface. These are also effective in some cases. Uncontrolled use of large volumes of solvent-based chemicals into the voids can produce potential hazards such as the increased risk of fire, staining of the plaster and other decorative finishes, etc.

5. Conclusion

On discovering insect attacks on timber, there are a few ways in which you can treat the wood, apart from using chemicals. Though chemicals provide good resistance, they are not always effective. The infested timber and furniture can be treated with heat to get rid of the wood-boring insects without any chemical assistance. Freezing the timber will also help but the process is difficult to get done. If the infestation is too wild for you to handle, don’t hesitate to call a professional for insect and pest control. Fumigation can help handle large infestations. But also make sure to note the cost required for assistance as well as the repair of the damaged timber. Check whether replacing the wood would be better than trying to maintain the attacked timber. If the condition of the timber is too bad, then there is no point in trying to save it.


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