Powderpost Beetles
(Coleoptera: Bostrichidae, Anobiidae)

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Apart from the pin- and shot-hole borers (Scolytidae and Platypodidae), there is a large number of mainly weevils (Curculionidae) and longicorn beetles (Cerambycidae) that are associated with wood. Most species of wood boring beetles attack dying or diseased trees or green timber, resulting in its degrade and only a few species of powderpost beetles (Bostrichidae, Anobiidae) can be found in dried wood causing structural damage of timber products.

The short antennae of the smaller powderpost or auger beetles are characterised by three flattened terminal segments. The black or brown powderpost beetles often have vertical elytra and are similar in shape and habits to some bark beetles. Both adults and the white, soft larvae are destructive borers of dry seasoned, unpainted or untreated timber and cane products.

Powderpost beetles usually attack seasoned timber and untreated timber products such as furniture and carvings, however some species infest living trees. They are named so because they produce fine, powder-like frass that can be found on the surface of the affected timber product. Before oviposition the females bite the wood, leaving several grooves. This probing is probably done to find out whether the wood contains sufficient starch, the essential food for the larvae. In case the wood is suitable, the female beetle lays a few eggs in the open pores of the sapwood. The developing larvae bore along the grain of the wood. For pupation the larvae tunnel towards the surface of the wood where they prepare a small oval pupation chamber. The adults surface through a round emergence hole about 1 to 2 mm in diameter. The holes are not stained as in the case of pin- and shot-hole borers. Characteristic also are the small piles of the powdery frass that are usually next to the holes or fall nearby. The re-infestation of the timber is common and can continue until the source of food is depleted. The conditions for a powderpost beetle attack are the moisture content of the wood which is maximum at around 15%; the size of the pores that has to be larger than the diameter of the female ovipositor; and the starch content that has to be high enough to nourish the larvae. Susceptible are Eucalyptus like E. torelliana that is mainly attacked after fire by Xylothrips religiosus, Dinoderus munutus and Xylopsocus gibbicollis. Some of the introduced pest species are Lyctus, Bostrychopsis, Heterobostrychus, Dinoderus, etc.

Reliable and efficient control measures against wood-boring beetles are are not available. However problems related to wood borers can be avoided by minimising the damage during pruning and thinning and other preventive measures as well as by avoiding forest fires.

Xylothrips religiosus
(reproduced from Gressitt, J.L. and Hornabrook, R.W., 1985)

Powderpost beetle damage on Eucalyptus spp.
(reproduced from Wylie, F.R. & Shanahan, P.J., 1973)

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Michael F. Schneider, 1999