Beetle adults are small (4mm) brown beetles that can fly into buildings
during the summer months, or are brought in from infested wood
(particularly partially seasoned firewood and old furniture).
They lay eggs in cracks, splits and fresh exit woodworm holes but
not on exposed wood. The
eggs hatch in the autumn and the emerging larvae eat the surrounding
wood to grow. The larvae bore tunnels (about 1-1.5mm in diameter) in the
wood, usually from 3 to 5 years. When
fully grown, the larvae pupate just below the wood surface and emerge as
fully grown adults in the Spring by biting through the wood surface
making the distinctive ‘woodworm holes’.
The adults live for only a few weeks to mate and for the females
to lay eggs to start the next generation.
The ‘woodworm’ eggs are laid directly on their potential
foodstuff. The emerging
larvae will happily eat most UK hardwoods such as beech, ash, oak,
walnut, and are particularly fond of the more nutritious outer sapwoods.
Heartwood oak and tropical hardwoods such as teak, mahogany and
rosewood are not normally attacked.
softwoods – such as pine etc., are all attacked.
particle boards, ply boards etc., are not normally vulnerable,
but pre 1950’s boards that were
glued with animal glued and some foreign boards glued with resin are
cardboard etc., can be attacked particularly if there is animal size or
animal glue used with them – such as in the
spines of books.
cellulose fibres such as cotton and linen are occasionally
attacked, again especially if animal sized or contaminated with animal
encouraging attack are:
warm temperatures above 10oC are necessary for the
larvae to develop. Temperatures
above 20oC encourage the adult beetles to fly and spread an
relative humidities above about 65% induce high moisture contents in
wood (above about 15%) necessary for Anobium
beetle development need even higher moisture contents.
poor environmental conditions can cause splits, cracks and
opening joints etc., that give good egg laying sites.
poor housekeeping and lack of cleanliness can encourage Anobium development.
of Anobium punctatum attack is
fresh exit holes in wood, from the emerging adult beetle.
They are small (~2mm diameter) clean cut holes, pale interior of
the hole, sometimes with a slight raised ‘crown’ round the edge.
- frass :
the pale coloured oval shaped pellets of digested wood often fall
out of the exit holes. The
frass has a gritty feel and the shape and size are obvious under a hand
adult beetles can often be found below the exit holes.
against woodborer infestations are of many types, including:
fumigation with toxic gases such as phosphine and carbon dioxide.
Fumigation is effective as the gas penetrates deeply into wood
etc., killing all stages of the insect.
It is useful when large quantities of material need to be treated
quickly. However, fumigants
are toxic and may react chemically with the objects being treated.
They also do not provide any residual protection against the
objects being reinfested.
anoxic fumigation provides very low oxygen environments, either
with inert gases such as nitrogen or with oxygen absorbers such as
suitably carried out, it can be a safe and effective method of killing
insects by asphyxiation and desiccation.
It does, however, need long treatment times of several weeks and
is not very effective against woodborers.
temperature manipulation using high and low temperatures will
kill insects. Temperatures
above 52oC will kill all stages – eggs, larvae, pupae and
adults in a few hours. This
is the basis of the Thermolignum system.
Temperatures of -30oC will kill all stages in 2-3
days, however at -18oC, the temperature of a domestic deep
freezer, up to 2 weeks is necessary.
Although generally safe on most materials, low temperature
treatments can damage by embrittlement and shrinkage of, for instance,
thick paint films.
insecticides consisting of an active ingredient in a solvent
system are effective and give residual protection.
Care must be taken in the choice of insecticide.
In some instances an organic solution base may be preferable to a
water solvent base.
Constrain is a water-based insecticide that is very effective
against woodborers and other insect pests as it penetrates deeply into
the wood. It is colourless
and odourless and is a very safe material recommended for domestic use.