Agriculture Reference
In-Depth Information
(fl owering trees) and softwood (cone-
bearing trees) due to the major differences
in wood cell anatomy (Thomas, 1977).
Beetles generally gain their food from the
major wood chemicals of cellulose, hemi-
cellulose, lignin and starch (Kartika and
Yoshimura, 2013) and digestion may in-
volve a complex of bacteria and yeasts
(Calderon and Berkov, 2012). The selection
of food is typically made by the female
upon landing and inspection of the timber,
which is followed by tasting before laying
eggs.
the technician measures moisture content
with a dielectric (capacitance) meter and
uses hand tools to tap timbers and check
variations of resonance. Detection of the
beetles is most likely at the stage where
some have completed their life cycle and
left emergence holes. The moisture meter
can give an estimate of moisture in sur-
rounding timbers, but the affected timber,
because of the lost density, may read lower
than the true moisture content. Generally,
in a structure, the beetles will be found
where moisture levels are elevated. In
tropical and coastal areas all the timbers
may be suitably moist but, at higher
latitudes and inland, moisture may become
a limiting factor.
When the species of beetles are of a re-
infesting variety or where a control measure
has been applied, it is useful to mark the
visible exit holes as an aid for future
inspections. For decorative timbers, this
can be done with a colour matching wax or
fi ller, whereas for non-decorative timbers
such as sub-fl oor and roof void framing, it is
useful to measure out an area (say a 100 mm
square) and mark all the existing holes with
a contrasting ink. Where a multitude of
timbers are to be marked, it is best to paste
paper strips over the holes.
Temperature
As with all insects, there is an optimal
temperature range for growth. Temperatures
that are too high (approximately 30-40°C)
or too low (approximately 5-15°C) will
prevent proper feeding and may cause
premature death but thermal limits vary
greatly between species.
Moisture
Beetles tend not to be active in fully
saturated wood because they need free
oxygen to reach their spiracles for breathing.
Some beetles, such as the anobiid genus
Hadrobregmus
, prefer timber that is above
fi bre saturation point where the free water
droplets sitting inside the cells promote the
growth of fungi. For
Lyctus brunneus
, the
fi bre saturation point represents the upper
moisture limit (Parkin, 1943). The main
pest beetles of houses have some capacity to
adjust to decreasing moisture content and
typically do this by extending their
developmental time.
Pest identifi cation
In regular maintenance inspections, beetles
are most commonly found by the presence
of exit holes. With local experience, it is
often possible to predict the pest species
based on the number, size, shape and
location of the holes. Within the species
range for exit hole size, the hole diameter is
a good predictor of adult size (Ciach and
Michalcewicz, 2013) and may also give
clues to the suitability of the substrate
(moisture, nutrition, etc.).
Detection of Infestation
Timber inspection
Specialist inspections
A typical timber pest inspection (in the
USA, a 'Wood Destroying Organism'
inspection) will involve the technician
using mostly visual techniques. In addition,
Beetle larvae in timber make only a limited
range of movements, tending to stay for
long periods at the working face of their
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