3. Cat Face - Fire Scar
A depression in the outer surface of a log
where the tree failed to renew following
an injury, such as an abrasion or fire scar.
4. Dead or Missing Side
Dead side is decay extending from the
surface to the core of a log, resembling a pie
shape in cross section of the log.
5. Lightning Scar
Lightning can damage a tree enough
to provide entrance of fungal spores or
cause other structural defects.
6. Constriction due to climber:
This defect occurs due to climbing
plants. These climbing plants do
considerable damage to the tree by
binding round the stem.
7. Worm Holes, Insect Damage
Insect burrows that are sufficient to result
in a significant loss of firm wood are not
common in healthy trees. However, storage
for long periods in salt water allows
torpedo borers to do extensive damage and
storage in land decks can allow boring
insects to infest the sapwood.
8. Burls
Burls are abnormal swellings of the
main stem or branches and are among
the most visible of the stem diseases.
9. DEFECTS DUE TO
CONVERSION
Timbers may sometimes contain defects
due to faulty conversion.
10. Machine burnt: Defect due to
overheating.
Machine notches: Due to bad holding
and pulling.
Miscut: Careless during sawing of wood.
Imperfect grain: Not matching with
grain alignment.
11. MECHANICAL DEFECTS
Regardless of how efficiently or carefully the
logging process is conducted, it will result in
some damage to trees when they are felled,
transported, and handled by various
mechanical devices
12. Undercut
A heavy undercut in a butt log will
reduce the amount of wood available
to cut lumber but no firm wood
deduction is made.
13. Barber Chair or Slab bed Logs
Barber chair is a very dangerous
occurrence, where the tree splits up the
trunk from the center during the
chopping process.
14. Shatter or Broken End
Shatter is another defect resulting from
the handling process When chopped, a tree
will often break or shatter if the stem hits a
rock or other object and also can be broken
during skidding, decking, loading, or
unloading.
15. Multiple Defects
Disease, environmental damage and
equipment damage will all affect the
volume of firm wood in a log.
17. Stain
Fungi causing stain in wood,
it feeds only on food materials
Stain defect does not affect strength
properties of wood.
18. Decay
This is observed due to wood destroying
These fungi nourish cell wall material
and break down the cell structure and
enzymatic activities.
This defect reduces the strength
properties of wood.
20. Insects
Insects borers and termites together
constitute one of the most destructive
biological agencies causing defects in
timber.
21. OTHER ANIMALS
Marine borer:
For example: Crustaceans, Mollusks’, etc.
Birds and mammals
For examples: birds, boar, deer
22. WOOD DECAY
Wood decay or wood rot is caused by fungi –
organisms that live on other organic matter
such as wood.
23. Brown Decay
Can delete up to 65% of the weight of
the timber.
Tends to spread from cell to cell fast.
Can be on the surface of the timber or
inside the wood.
In the advanced stage, timber often
forms into cube like appearance.
24. White Decay
Can delete up to 100% of Timber weight
Cells decompose from the center outwards
and completely destroy the cell before
moving onto the next cell.
Can be on the surface or inside the wood.
In the advanced stage, the timber has a
hard appearance.
25. Soft Decay
Generally wood is a darkish color.
Usually found on the expanded surface
of the wood and extending inwards.
26. Mold
They feed on the contents of the cells
No effect on the strength of the timber
When the timber dries the mold cannot
continue
Molds are indicators of high moisture
content in the air
27. TABLE 1: CAUSES OF DECAY
Type Agent Environmental Factors
Biological fungi (dry rot, wet rot, moulds and
others) bacteria; actinomycetes; lichens,
mosses and algae wood-boring insect
larvae (woodworm,death watch beetle
and others) carpet beetle, moths, book
lice and silverfish termites
moisture and humidity
air movement
temperature
light
dust
food source
Chemical acids, alkalis and solvents pollution
remedial treatment
Physical mechanical abrasion, general handling
and others, decomposition by physical
agents such as prolonged heating, fire
and moisture
normal use, visitor wear
accidental damage
sunlight, heating, fire,
damp
Radiation ultraviolet light exposure to sunlight
28. Brown cubical butt decay
(Phaeolus schweinitzii) in pine.
root decay (Inonotus tomentosus)
in pine.
TYPES OF DECAY
