Wood-Boring Beetles

This exotic wood-boring beetle of the family Bostrychidae (one of the commonly called 'false powder-post beetles'), with its large, distinctive and rather menacing thoracic horns, is found in parts of Africa and Arabia. It is often imported to Europe (and sometimes to Britain) in timber. I get occasional enquiries about this beetle when specimens emerge from ethnic wooden bowls and ornaments that people have purchased abroad and brought back to the UK as tourist souvenirs!

And Some British Relatives . . . . . .

The tropical Bostrychoplites, pictured above, is closely related to some of our British wood-boring beetles, such as the true powder-post beetles (Lyctus spp.) that belong to the family Lyctidae, and also to members of the family Anobiidae, including the notorious death-watch beetle (Xestobium rufovillosum) and the common woodworm or furniture beetle (Anobium punctatum).

Piece of oak timber with exit holes of
death-watch beetle & furniture beetle

The larvae (or grubs) of these beetles tunnel into dead wood, including furniture and the structural timbers of buildings, and can quickly reduce it to sawdust. Their presence often goes unnoticed until the adult beetles emerge, leaving behind the familiar tell-tale signs of 'worm-holes'.

The piece of oak in the first photograph has exit holes of death-watch beetle (larger holes, actual diameter about 3-4 mm) and furniture beetle (smaller holes, diameter about 2 mm). The second photograph, shows similar, small exit holes left by powder-post beetle.

Wood attacked by
powder-post beetle

In addition to powder-post, death-watch and furniture beetles, there are several other wood-boring species that frequently invade buildings and may likewise attack and damage wooden fittings and/or structural timbers. These include Ptilinus pectinicornis, Hylotrupes bajulus (the house longhorn), Nacerdes melanura (the warf borer) and two wood-boring weevils, Pentarthrum huttoni and the very similar introduced species, Euophyrum confine.

Ptilinus pectinicornis, male
(body length 4-5 mm)

Hylotrupes bajulus
(body length 10-25 mm)

Nacerdes melanura
(body length 7-12 mm)

Pentarthrum huttoni
(body length 2-4 mm)

Control of Domestic Wood-Boring Beetles

Since damage by wood-boring beetles nearly always has its source in eggs laid by the female, one important method of prevention is to take care that infested wood, particularly infested furniture, is not introduced into the house, or if the furniture cannot be dispensed with, to take steps to eradicate the infestation while it is still localized. Wood can be protected from infestation and existing infestations eradicated by treatment with a commercial wood preservative, persistent contact insecticidal fluid, or preservative-insecticide mixture sold for 'woodworm' control. These chemicals are made up in appropriate solvents designed to give maximum penetration of the wood and can be applied by brushing, spraying or pressure-injection (although the latter method usually requires the services of a specialist pest control company). Commercial products for household use should be available from hardware stores, garden centres and other retail outlets that stock household and garden insecticides. Ask your local stockist for advice on the range of approved products available in your area or country, since this varies from place to place.

The success of insecticide treatment depends largely on the thoroughness with which the fluid is applied. Special attention should be given to any rough, unpainted or unpolished surfaces, such as backs, insides and bottoms of pieces of furniture, for these are the places where eggs are laid. In addition to brushing or spraying the fluid over all free surfaces, it should if possible be injected into the exit holes using a small syringe. After treatment it is best to fill all the exit holes with wax, or if you wish to hide the holes completely, with plaster or wood-filler which can be stained and polished to match the wood. Filling the holes makes it easier to detect the appearance of any fresh holes and so decide when the infestation has ended.

The best time to apply insecticides to wood is in spring (March-May) when the insects are near the surface of the wood, just before they emerge, and so are more accessible to the insecticide. The life cycle of most wood-boring beetles lasts more than one year, so that to achieve complete eradication it is essential to repeat the treatment each year until signs of the attack disappear. The treatment of house timbers is usually a task for a specialist firm. Where the attack has been so severe that the strength of timbers is affected, replacement of parts may be unavoidable. Floorboards, panelling, etc., may have to be removed in order to treat the under surfaces and joists. In confined areas such as roof spaces, attics or cellars, the use of insecticide fumigation or smoke generators offer a means of preventing re-infestation by killing the adult beetles. Consult a specialist pest control company in dealing with any extensive problem of this kind, especially where structural timbers may be involved.

REMEMBER TO USE INSECTICIDES SAFELY AND FOLLOW ALL THE INSTRUCTIONS ON THE PRODUCT LABEL

Further Reading

• Britton, EB. 1961. Domestic Wood-boring Beetles. British Museum (Natural History) Economic Series No. 11A. London, British Museum (Natural History). 40pp.
• Duffy, EAJ. 1953. A Monograph of the Immature Stages of British and Imported Timber Beetles. London, British Museum (Natural History). 350pp.
• Hickin, NE. 1975. The Insect Factor In Wood Decay. The Rentokil Library. London, Associated Business Programmes Ltd. 383pp.