Management Strategies for Subterranean Termites - Urban Insect Pests: Sustainable Management Strategies - page 117

Conventional soil treatment

Scheffrahn (2010) recommended additional
inspections and treatment of pleasure craft
as necessary methods of preventing the
invasion of termites.
In Brazil, the transport of living plants
with soil, rubbish, waste materials and
earth with vegetable material seems to be
means by which C. gestroi has spread
(Fontes and Milano, 2002). The shipment of
termite-infested railroad sleepers is another
means of transporting subterranean termites
to new locations (Evans et al. , 2013).

Soil treatments remain the mainstay of the
industry to control subterranean termites,
accounting for >80% of the control practices
in the USA (Su, 2011). In the past 15 years,
a number of new insecticides have been
registered for soil treatment. In a com-
prehensive review, Hu (2011) categorizes
these as repellent fast-acting or non-
repellent slow-acting toxicants. The slow-
acting insecticides can be further categorized
as those producing dose-independent re-
sponses such as the CSIs and those pro-
ducing dose-dependent toxicity such as
fi pronil and imidacloprid (Rust and Saran,
2008). The slow-acting active ingredients
have revolutionized soil treatments. Peri-
meter and spot treatments have replaced the
more extensive and thorough treatments.
The contact toxicity (LD 50 ) of these newest
active ingredients against R. fl avipes from
highest to lowest is: fi pronil (0.12 ng/
termite) > bifenthrin > chlorantraniliprole >
cyantraniliprole > imidacloprid > chlor-
fenapyr > indoxacarb (13.88 ng/termite).
The ranking for C. formosanus is fi pronil
(0.20 ng/termite) > imidacloprid > chlor-
antraniliprole > cyanthraniliprole > bifen-
thrin > chlorfenapyr > indoxacarb (17.16
ng/termite) (Mao et al. , 2011). Notably many
of them are more toxic to termites than
previously used chlorinated hydrocarbons,
organophosphates and pyrethroids.
Fujimoto et al. (2012) summed up the
fi ndings of numerous researchers and con-
cluded that the pyrethroids are highly
repellent to C. formosanus , and the
neonicotinoids, fi pronil, chlorfenapyr and
chlorantraniprole are not.
Even though many of these new active
ingredients are extremely toxic on contact,
they exhibit delayed toxicity, explaining
why so many of them are horizontally
transferred during grooming. Quarcoo et al.
(2010) wrote: 'Termiticide-induced behaviors
such as ataxia, moribundity, release of fl uid
(protodeal or stomodeal), reduced mobility,
impaired tunneling (excavation) and avoid-
ance (of repellent compounds) have signifi -
cant impact on control efforts'. Colony
vigour and density also affect insecticide

Control Strategies

The primary control strategies for sub-
terranean termites rely on the use of chemi-
cals. The types of insecticides and their use
have dramatically changed during the past
60 years because of environmental con-
cerns, availability of new chemistries,
advances in insect toxicology and regu-
latory changes. Persistence and longevity
were once the gold standards for in-
secticides applied to soil to remedially
control termites. Now, many of the newly
registered soil insecticides have more
favourable environmental attributes, pro-
vide delayed toxicity and are non repellent
to tunnelling termites. CSIs that prevent
insects from producing cuticle during
moults are now widely incorporated into
termite baits. There continues to also be a
keen interest in isolating chemicals derived
from natural sources that deter feeding and
kill termites.
Even though the primary focus has been
on chemicals, advances in physical and
cultural control that have the potential to
prevent termites from attacking structures
have been recognized. Ahmed et al. (2004)
has presented a review of the various
physical control measures being utilized in
Australia. The use of concrete slabs can be
an effective barrier as long as cracks do not
exceed 711 μm for R. fl avipes or the height
of the head capsule of other termite species
(Tucker et al. , 2011). Cost remains an issue,
however, in using particle barriers,
pyrethroid-impregnated barriers, stainless
steel mesh and other physical barriers.