Series editors' preface - Wood Tools

300 Conservation of Furniture
beetles may develop faster in fungal infested
wood (Simmonds, 1997). The timber most
frequently attacked in buildings is oak
although damage has also been recorded in
alder, beech, chestnut, elm and walnut. In its
wild habitat the beetle also attacks a variety of
other hardwood trees. Tropical hardwoods, by
virtue of their generally greater resistance to
fungal decay, may be less susceptible to
attack. Softwoods appear to be attacked only
when they are in close proximity to infested
hardwoods. Attack mostly occurs in timber
which was installed in an unseasoned condition
or which has subsequently become wet
for prolonged periods. Damage to installed
items such as pews and screens occurs but
damage to free-standing furniture is rare,
although not unknown (see Figure 7.5).
The frass from the death watch beetle is
coarser than that from common furniture
beetle and contains bun-shaped faecal pellets
in contrast to the finer dust and ellipsoid
pellets produced by the common furniture
beetle (see Figure 7.7). Presence of frass, clean
sharp holes and the presence of living beetles
on or near damaged timbers or on the floor
underneath affected timbers are good indications
of active infestation. The severity of
attack can be judged up to a point by the
number of flight holes present but because
death watch beetle can bore deeply into
timbers it may be necessary to carry out
exploratory drilling to determine the full extent
of the infestation and hence the structural
implications of the attack and the remedial
measures to be taken.
Preventive measures chiefly consist of elimination
of conditions favourable to attack, that
is of maintaining the building or other wooden
structure in good condition free from damp
(Melville and Gordon, 1984). Particular attention
should be paid to roof coverings, gutters,
rain-water pipes, damp-proof courses, broken
or badly sealed windows and other structural
defects which could allow the penetration of
damp and the creation of conditions from
which an attack could proceed. Regular
inspections inside and outside can help to
ensure the integrity of the building and
freedom from damp. Determination of the
extent and distribution of attack and of the
structural condition of the timber are essential
precursors to any remedial treatment.
Powder post beetle (Lyctus spp.) Powder post
beetle larvae are so called because they
reduce the sapwood of many partially or fully
seasoned timbers to a fine flour-like powder.
Powder post beetles are found in several
different families, of which two of the most
common are the Lyctidae and the
Bostrychidae, and are distributed world wide.
The commonest species in the United
Kingdom is Lyctus brunneus, a small reddish
brown or black beetle about 5 mm long and
of somewhat flattened appearance. The curved
white larva of this species are 5–6 mm long
when fully grown and are distinguished by a
pair of oval brown spots (spiracles) near their
posterior end, which are visible with a 10
hand lens.
Development from egg laying to emergence
normally takes one to two years. It may take
longer under unfavourable conditions but in
heated buildings may take only eight to ten
months. Emergence mostly occurs from late
May to early September with a peak in July.
The larvae feed mainly on the cell contents
(starch) of sapwood although they may
emerge through adjacent hardwood, leaving a
circular exit hole approximately 1.5 mm in
diameter. The small thread-like larval tunnels
running mainly parallel to the grain which are
characteristic of the early stages of attack may
be revealed when wood is machined but are
easily overlooked. In its later stages, the
sapwood may be almost completely disintegrated
although a thin skin is usually left on
the surface. The frass is extremely fine, like
talc.
Most commercial hardwoods, including oak,
ash, elm, walnut, hickory and mahogany
which contain a normal amount of starch are
attacked, those with large pores are preferred.
Veneers and plywoods are also susceptible.
Fine textured timbers such as beech and birch,
in which the vessels are less than 0.1 mm in
diameter are normally too small to admit the
ovipositor of the female and are therefore
immune. Most softwoods are also normally
immune since vessels are absent. Lyctus is a
pest mainly of sawmills, timber yards and
wood manufacturing premises and strenuous
efforts are needed in these environments to
prevent Lyctus infestation. Good hygiene and
regular inspection are essential but not
normally sufficient. Active control methods