The
most frequent insect pest in wood in buildings in the UK is the common furniture
beetle, Anobium punctatum, better known as woodworm.
It has a 5 year life cycle, maximum. We need to look at wood preservatives and
their performance - wood treatment is always aimed at breaking the egg laying
cycle - so what is that cycle and how does it influence insecticide treatment? Common
furniture beetle starts life as an egg; these are laid on a suitable timber surfaces
- but some of these surfaces are cracks and crevices, end grain and, very importantly,
down the old emergence holes in pupal chambers and tunnels. The larvae hatch,
bore into the sap wood when they remain causing the damage; the larvae are the
feeding and growing stages and are by far the longest stage of the insect's life
cycle. At some stage the
larva moves close to the surface and constructs a pupal chamber in which it pupates.
Between May and August the adult emerges from its pupal skin and chews its way
out leaving the familiar woodworm holes. When they cut their way out they do not
feed! When emerged they mate and lay eggs, frequently rapidly and very often down
the old emergence holes in the pupal chambers and tunnels, i.e.. well below the
surface. Indeed, both mating and egg laying can take place within the emergence
hole itself.
Spray
applied preservatives: The
spray applied timber preservative can contain a contact insecticide such as Permethrin
or Cypermethrin. Basically all the insect has to do is to come into contact with
this material - the insect doesn't have to ingest it; if it did it would also
kill it. So one could theoretically argue that contact insecticide has both stomach
and contact action. Using an alternative Insecticide, like a Boron based product,
only kills the 'grub' or lava when it eats wood. It acts as a stomach 'poison'
by affecting the enzymes in the gut. The advantage of this type of treatment is
that it does NOT kill flies or spiders - only wood borers - therefore leaving
them for the Bats. Boron based products are also superior because that have no
vapour - so the active part - the Borate - never leaves the timber, giving permanent
protection. When the wood
is sprayed with the preservative it penetrates the surface, probably between 2-6
mm, to leave a protective 'envelope' of insecticide. Any stages initially deluged
by the fluid in the 'envelope' will be killed. Those remaining beneath the treatment
will survive and continue activity. Clearly these stages will have to come into
contact with the insecticidal 'envelope' at some stage for it to be effective.
This occurs, at least theoretically, when (a) adults emerge, and (b) larvae hatch
from surface laid eggs. The
adults: Adults should be killed as they try to cut their way out of the wood when
they cross the 'envelope' containing the contact insecticide; remember they do
not feed and must come into contact with the insecticide to have an effect. Therefore
the contact acting insecticide should not let them through the treated envelope
(non contact insecticides will have no effect on this stage). Indeed, both Permethrin
and Cypermethrin like most pyrethroid derived insecticides, are fast acting. Since
it does take time to cut emergence tunnels clearly one would expect these beetles
to be affected quite rapidly. If under such circumstances, however, they can completely
emerge successfully then they haven't been affected by the treatment: they are
then free to mate and lay eggs.
Egg
larvae:
It is well documented that common furniture beetle mates and lays eggs down old
tunnels, often well below the surface. This frequently put the eggs and larvae
subsequently hatching beneath the applied treatment, be it a contact insecticide
or non contact type insecticide. As such this will lead to successful hatching
and larval survival. Hence the infestation continues, and the treatment must therefore
be deemed to have failed. After all if you cannot prevent emergence and you cannot
prevent egg laying, larval hatching and survival then you have failure.
Books
- guides to insects, rots, moulds and damp Identifying
Wood Boring Insects, Rots and Moulds: full colour: BRE - £55.00 Buy
BRE Book -  Identifying
Dampness in Buildings: Coleman - Reprint - £9.99 Buy
Coleman Book -
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Repair Systems, Unit
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TQ12 2SN T:
01626 331351 F: 01626 331143
E: help@propertyrepairsystems.co.uk
Other
Property Repair Systems Sites: www.dampness-info.co.uk
- how to treat penetrating dampness in walls and plaster www.deck-treatment.co.uk
- how to treat patio decks and yacht decks www.dryrot.biz
- how to cure and prevent Dry Rot www.epoxy-info.co.uk
- epoxies, polyesters and polyurethanes for all applications www.furniture-outdoors.com
- all weather cane garden furniture, luxury Danish designs www.joist-repair.co.uk
- how to quickly repair joists and beams of any size www.propertyrepairsystems.co.uk
- fire retardant paints, hygiene products, metal bracket manufacture, crack injection www.timber.org.uk
- systems of repair, with step by step methods www.timber-repair.co.uk
- how to repair timbers in buildings without wrecking the place www.woodworm-info.co.uk
- how to kill and prevent woodworm and death watch beetle
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