The hard fibrous material that forms the main substance of the trunk or branches of a tree or shrub, used for fuel or timber. Wood is a versatile material with many uses, namely: for building shelter, wood works, canoes, for making paper, for coal production etc

1. MCB 377:
WOOD BIODETERIORATION
DR RUTH AFUNWA

2. INTRODUCTION
The hard fibrous material that forms the main
substance of the trunk or branches of a tree or
shrub, used for fuel or timber.
Wood is a versatile material with many uses,
namely: for building shelter, wood works,
canoes, for making paper, for coal production
etc

3. Wood is by far, the most versatile and beautiful
building material available to man.
It has been with us since man first started to
build his own shelter.
It is the only building material that is subject to
destruction by biological agencies, such as
fungi and insects.
This is one of the inherent disadvantages of
using wood as a building material.

4. WHY WOOD IS ATTACKED?
Wood is a natural plant material, and as such, is
made up of a host of organic compounds,
many of which represent a food source for the
attacking agents. Wood is made up of cells,
which are in turn, made from cellulose (and
often strengthened with lignin deposits).
Cellulose is a rich source of carbohydrate

5. Wood is actually a very inert material, i.e., it
does not go into chemical reactions that will
actually destroy the material. It is surprisingly
immune to acids, alkalis, and strong
detergents. This, in fact makes paper making a
tough proposition as wood is not easily
converted to pulp by chemical means.

6. • Bacteria and viruses also do not have any
significant effect on wood.
• Bacteria attack is secondary in nature, i.e.,
something else did the first bite.
• For both fungi and insects; they have evolved
elaborate mechanisms for the digestion of
cellulose. The cells also contain other
compounds, such as starch, which is also a
source of carbohydrate for these attacking
agents. In other words, when an insect attacks
a piece of wood, it is merely having a meal.

7. AGENTS THAT ATTACK WOOD
Biological agents that commonly attack wood,
and they are:-
● Fungi
● Insects, including beetles, termites, and
occasionally, bees and ants
● Marine and fresh water borers (plankton)
mixed population of organisms

8. Fungi and Wood
Fungi attack wood through feeding on the wood cells.
There are two modes of feeding; some fungi feed on the
cellular contents of the wood.
In this case, the structure of the cell-wall is not destroyed,
and the wood retains all its strength.
Examples of these types of fungi are the sapstain fungi.
When a piece of wood is attacked by a sapstain fungus,
the attacked portion may turn blue or black (that is why
the fungus is sometimes known as ‘bluestain fungus’).
There is no loss of strength. This is why “bluestained”
or “sapstained” timber is perfectly safe to use for
construction,

9. The main food found in the cell contents are
sugar and starch, and since the sapwood tend
to be the depository for both these material,
sapwood is more susceptible to attacks by
these fungi.

10. The other type of fungi is more destructive. They
feed on the cell-wall material, breaking down
the cellulose that makes up the structure of
these walls. Through this type of attacks, the
wood loses its integrity and breakdowns into a
lump of spongy mass. This is the rot you see in
‘rotten wood’.

11. WOOD ROT
• There are many types of rots, depending on the
fungi involved. Namely:
• wet rot
• dry rot
• white rot and
• brown rot.

12. In all cases, wood that is attacked by wood
rotting fungi will lose its load bearing capacity
and should be replaced immediately. Since
wood rotting fungi attack the wood cells
directly, both sapwood and heartwood are
equally susceptible

13. PREVENTIVE MEASURES
For a biological agent to survive, three
conditions must be available, i.e.,
oxygen, water, and food. Therefore,
biodeterioration of wood can be
prevented if one or more of these
conditions are eliminated. This forms the
principle for protecting timber from
biodeterioration.

14. For example, keeping the wood totally immersed
in water will cut off the oxygen supply, making
it impossible for the attacking agents to
survive and thus preserving the wood.
This principle is used for piling works, where the
timber piles are driven into the water-table,
thus ensuring that the timber is totally soaked
at all times.

15. Timbers that are kept dry at all times
will go a long way to prevent the
attacks of many organisms, such as
fungal attacks.
It is when timbers are subject to wet
and- dry conditions, such as keeping
them in the rain, that they run into
greater risk of being attacked.

16. Finally, if the food source, i.e., the wood
cells and their contents are made
unpalatable to the attacking agents, then
there will be no attacks.
This can be done through the introduction
of chemicals such as preservatives.

17. Fungal Attacks
Moisture content of the wood determines level of
destruction.
If there is enough water present, then the fungi will
flourish.
The prime preventive measure is to keep the wood
absolutely dry. If this is not possible, such as in
outdoor conditions, then the alternative is to
prevent the fungi from getting to the food source.
This can be achieved by chemically treating the
timber with a preservative containing a fungicide.

18. For preventing sapstain, especially in the lighter
coloured timbers, it is best to treat the timber
off-the-saw with a preservative.
Sapstain fungal attack can occur very quickly
and permanent damage can be done if the
timber is not treated immediately and it is
difficult to get rid of them.