Dear John,
We live in a village house in Parcent and the attic roof timbers have many woodworm holes. Can you suggest any safe woodworm fluid for treating this as we are particularly concerned for our children's health and also I am asthmatic.  We have also recently installed two modern timber Velux windows and may need to protect these from the woodworm and lastly is this likely to spread to the rest of the house. What would you suggest we do?

Julia P

Hi Julia,

I do not have the figures for Spain but in the UK approximately 5000 British homes are sprayed with toxic chemicals to kill woodworm every year, woodworm that probably left the wood 100 years ago.

The problem with woodworm is that when they leave the wood they also leave holes and the holes are used by woodworm treatment salesmen to convince householders that they have a problem. But the truth is that the holes are probably many years old and spraying them with chemicals is a classic case of shutting the stable door after the horse has bolted.

There are many types of wood-boring insects and in nature they play a vital role in the decomposition of forest timber, as well as providing a vital food source for other species such as birds. Woodworm is a name given to many types of boring insects that spend most of their life as a maggot before pupating and emerging for a short adult life as a flying beetle, so the woodworm is actually the larval stage of a beetle.
The adult female beetle lays her eggs in an environment which will offer the best chances of survival for her offspring, which means moist sapwood. Moist, because the larvae need moisture to survive and sapwood (the outer living part of the tree) because this is where the minerals and nutrients are to be found.

The woodworm larvae spend three to five years burrowing around in the sapwood before hatching out as adult beetles and munching their way to the surface, where they leave the characteristic flight hole. My past experiences lead me to believe that most of this activity occurs in the first ten years after the house was built or when new timber is introduced into the property. After that, the sapwood will have dried out and become less appetizing and the adult female beetles will prefer to lay their eggs in a more preferable location, such as dead trees in the garden. This is especially true in recent times, when older homes now have central heating which dries timbers down to below the 11% moisture content needed to support insect life. Woodworm is not infectious and there is no reason why it would spread from one part of the house to another. As each infestation results from the female adult beetle laying eggs in an environment that she thinks will be suitable for her offspring, and you have moist nutritious wood anywhere in your house, then adult female beetles (which are flying around everywhere between April and July) will lay eggs in it. If the wood is dry, as it normally is in Spain and you live in a heated and ventilated house, then they won't. Once this generation has hatched out and flown then that will probably be the end of it - regardless of how many chemicals you spray around the place.

Firstly try to establish that you actually have live woodworm by looking for signs of powdered wood on the floor below the affected areas and secondly by putting your ear to the wood and listening for them merrily munching away. I would think that unless the attic timbers are fairly new it is very unlikely that you have woodworm. I cannot really recommend any woodworm fluids as they are all nerve poisons and there is no justification for using insecticides unless you have definitive evidence that there is a continuing active problem. Your new Velux windows are unlikely to be affected by woodworm as the wood is kiln-dried and sealed with a water-based varnish. If you are still concerned and would like me to have a look at the roof timbers just give me a call.

John Phillips (F.I.A.S. F.A.B.E. M.I.B.C.O. F.F.B. M.R.S.H. C.M.W.O.B.O. M.B.I.M)
Construction Buena Vista

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