Urban Timber Pest Beetles: Risks and Management - Urban Insect Pests: Sustainable Management Strategies - page 159

of fumigant assessments is the diffi culty in
obtaining the pests in suffi cient numbers
(Schortemeyer et al ., 2011).

(Querner et al ., 2013). But because such
traps collect emerged adult beetles, the
method is not suitable for complete control
of active infestation.

Conventional insecticides

Physical

There is a long history of beetle control
using sprayed or injected insecticide that
has been dissolved in an organic solvent to
improve penetration. More recent insecti-
cide registrations use water as the carrier.
Permethrin is the most widely used of the
many pyrethroid insecticides, though solu-
tions of various formulations of boron are
available and water-based boron is seen as a
more sustainable solution (Graf et al ., 1998).
One issue with liquids applied to interior
timbers is persistent odour so, although an
organic solvent formulation may penetrate
more thoroughly, a water-based application
is often preferable. Getting the required
chemical dose to reach all the beetles may
not be possible. Adding too much water to a
timber causes swelling and consequent re-
drying may leave the timber with a changed
shape or appearance. Chemical treatments
penetrate best when there are already
suffi cient beetle exit holes to provide easy
routes deep into the timber. Some larvae
may still escape a lethal dose, especially
those that pack their frass, at least until they
pupate and try to emerge through the treated
surface. It is advisable that chemical appli-
cations be accompanied with a warning that
some adult beetles may still emerge from
the treated timbers. Kill rates can be
improved by combining surface treatment
with direct injection, but this is a slow and
laborious process that may exceed the cost
of timber replacement without guaranteeing
a total kill.

Excess heat or cold are effective control
measures and the subject was reviewed by
Strang (1992). This methodology carries a
timber damage risk because, for example,
freezing damp timber creates large ice
crystals or heating French polished furni-
ture melts the shellac. More moderate
application of heat or cold combined with
other actions such as fumigation or modifi ed
atmosphere may potentially produce a more
reliable result (Wijayaratne et al. , 2012).
Gamma radiation has been tried (Bletchly,
1958, 1962) but the beetle eggs were found
to be highly resistant, making the process
unreliable. Raus et al . (2009) exposed
Hylotrupes bajulus to a magnetic fi eld that
was more than 4000 times stronger than the
Earth's natural fi eld. The unexpected result
was a signifi cant increase in vitality. Micro-
wave radiation by comparison is a successful
method (Novotny et al ., 2013) and has
opportunities to become a commercially
viable application method (Kisternaya and
Kozlov, 2007). Electrocution, which has
been used with limited success on drywood
termites (Lewis and Haverty, 1996), does
not seem to have effi cacy against timber
pest beetles.

Modifying Construction Methods

Moisture control

Keeping timbers relatively dry can almost
eliminate risk from beetle infestations for
some species such as Anobium punctatum
(Pinniger 1996). Examples of good building
design to reduce beetle risk are the provision
of wide eaves to reduce external wall
wetting and sub-fl oor vents that allow
airfl ow to clear excess moisture from the
ground fl oor.

Trapping

Traps with aggregating pheromones can be
useful to limit ambrosia beetle incidence at
sawmills (Lindgren and Borden, 1983),
reduce the spread of invasive pests (Gove et
al ., 2007) and detect activity in museums