Insecticide or fungicide: choosing your treatment
Wood is a "living" material that contains a multitude of substances that are palatable to many organisms. The presence of wood-boring insects and wood-eating fungi in wood is highly damaging as it jeopardises the structural durability of the material and therefore the durability of the structure.
Treating wood, either preventively (avoiding the establishment of these organisms) or curatively (stopping their proliferation and the damage they cause), may, in certain very specific cases, prove necessary. Insecticides and fungicides are not without risk either for the environment or for the applicator.
Therefore, in order to avoid treating "all over the place", especially if it is not or no longer necessary, it is important to make the right diagnosis. The editorial content below is intended to help you in this respect and also suggests some golden rules to be followed to avoid any treatment. You will also see that in this category we have selected insecticide treatment products for wood that are not of our own manufacture. The criteria that led us to choose these products are technical performance but above all the ecological aspect.
NATURAL INSECTICIDES FOR WOOD
WOOD-EATING INSECTS AND LIGNIVOROUS FUNGI: SHORT OVERVIEW
There are 5 main species of wood-eating insects that are the most widespread in France:
- the house longhorn beetle that attacks softwoods
- the broadleaf longhorn beetle, also known as Trichoferus holosericeus
- the furniture beetle, which attacks both deciduous and coniferous trees
- the deathwatch beetle, which has the habit of attacking wood that has already undergone fungal degradation (cubic or fibrous) and has a high moisture content
- the powder-post beetle, which prefers soft woods.
Although each of these insects has its own mode of development, they all have in common that they all feed on starch, a nutrient that is only present in the sapwood, which is the peripheral (i.e. "youngest") part of a tree. When this sapwood is transformed into heartwood (also called duramen) through the process of hardening, the starch is then transformed into other molecules. The heartwood then becomes unsuitable for insects.
As far as lignivorous fungi are concerned, their classification is done, in practice, according to the type of rot it causes (visual examination).
There are 3 main types of rot, the development of which occurs as soon as the moisture content of the wood exceeds 20% :
- brown or cubic rot, which preferentially degrades the cellulose (the wood is then darkened due to the high remaining lignin content). The most frequent and best-known representative of all is the dry rot (Serpulan lacrymans). The humidity of the wood must be above 20%
- white or fibrous rot, which attacks mainly lignin (reveals the cellulose fibres) and occurs on wood with a moisture content of more than 40%. Bracket fungi is the most common.
- soft rot which attacks very damp wood (humidity over 50-60%)
AVOID TREATMENTS ? THE GOLDEN RULES
Preserving the environment and human health rather than wood is possible by respecting a few simple principles :
- Favour a naturally durable species or at least apply the right "wood in the right place" principle by using a species with a level of natural durability suitable for its use. To do this, we will refer to the 5 possible use classes (from I to V) which will be used to make the appropriate choice of wood classified according to 5 durability levels (from 1: very durable to 5: perishable).
- Use wood purged of sapwood, the presence of which increases the risk of attack by insects attracted by the starch,
- Use very dry wood and limit or even eliminate any risk of re-moistening of the wood by respecting the rules of good work practices (appropriate construction choices and adherence to the building regulations). This ensures that the humidity level of the wood remains below 20%, the limit below which lignivorous fungi cannot develop.
WHEN, HOW AND WHY TREAT WOOD?
RECEIVED IDEAS AND ABERRATIONS
Some users' behaviour lacks sense because of their lack of knowledge in the field, but above all because of the incentive from the chemical industry, which encourages consumers' fears of seeing their wood deteriorate.
Here are some of the most striking examples:
- Using wood treated in an autoclave with heavy metals (considered as hazardous waste at the end of its life and for which no reprocessing channel exists) for temporary uses or which at least do not require such a level of protection with regard to their lifespan. The example of autoclaved pine garden borders is symptomatic: who plans to keep this type of product for more than 20 years?
- Applying a fungicide to wood wich has a sufficient level of natural durability for the intended use.