Agriculture Reference
In-Depth Information
telephone poles in open or sealed tanks
(Randall and Doody, 1934b). The mode of
action in killing drywood termites due to
excess heat are complex and involve hyper-
thermia at the cellular level leading to the
disruption of cell membranes and destabil-
ization of enzymes (Bowler, 1981; Ebeling,
1994). Commercial applications using pro-
pane heaters for structures fi rst appeared in
the 1980s (Forbes and Ebeling, 1987). More
recent advances in heating technology
operate using infrared heaters powered by
electricity (Getty
et al
., 2008). Preparations
for whole-structure heating are similar to
fumigation. Tarpaulins are wrapped around
a structure; however, unlike fumigation the
tarpaulins have holes to aid the displacement
of cooler air with heated air. Electric fans
are also used to aid the movement of heated
air within the structure. Thermocouples
must be installed throughout the structure
to aid in monitoring temperature in the
wood undergoing treatment. Treatment
time is variable depending on the size of the
structure, and several hours to days may be
needed to complete the process (Ebeling,
1994; Woodrow and Grace, 1998b). When
the temperature of the infested wood
exceeds 48.9˚C for at least 1 h, laboratory
and fi eld investigations have reported
eradication for fi ve species of drywood
termites (Ebeling, 1994; Lewis and Haverty,
1996; Rust and Reierson, 1998; Scheffrahn
et al
., 1997b; Woodrow and Grace, 1998b,c).
However, certain construction features (e.g.
wood touching concrete and large volumes
of wood) can be diffi cult to heat to lethal
temperatures (Randall and Doody, 1934b;
Ebeling, 1975; Lewis and Haverty, 1996).
Damage to a test structure, warping of wood
(sticking doors) and warping of a plastic
(ABS) wastewater pipe have also been
reported (Lewis and Haverty, 1996). Heat as
a drywood termite intervention has seen
increased use as a whole-structure treatment
option (Lewis, 2003).
At the opposite end of the temperature
continuum, liquid nitrogen has been tested
in laboratory and fi eld effi cacy trials against
drywood termites as a local intervention
that employs very low temperatures (Forbes
and Ebeling, 1986; Lewis and Haverty, 1996;
Rust
et al
., 1997; Rust and Reierson, 1998).
The mode of action in killing drywood
termites using excessive cold temperatures
involves the formation of ice crystals in the
haemolymph that disrupt and destroy
cellular membranes leading to the eventual
death of the insect (Heinrich, 1981). Cur-
rently, it is not known if the use of excessive
cold to control drywood termites is still
available as a service option to consumers
(V.R. Lewis, California, 2013, personal com-
munication).
Fumigation
The use of fumigants for controlling termites
has a long history that also has seen con-
siderable change in products, applications
and safety procedures. The earliest reports
on fumigation are from 1863 and involve
the use of nitric oxide, chlorine and sulfur
dioxide gases that were not very effective
and were hazardous to use in structures
(Randall
et al.
, 1934b). By the 1930s, eight
additional fumigants were tested including
benzene, carbon bisulfi de, carbon tetra-
chloride, chloropicrin, hydrogen cyanide,
para-dichlorobenzene, naphthalene and
turpentine, with only hydrogen cyanide
deemed to be effective (Randall
et al.
,
1934b). Preparation of structures for fumi-
gation in the mid-20th century involved the
use of moistened paper tape affi xed around
doors and windows to contain the fumigant
during treatment and there was no require-
ment for personal protective equipment or
an aeration plan for structures (Hennessy,
1993).
During the 1940s and 1950s, methyl
bromide (MB) and sulfuryl fl uoride (SF)
were developed as fumigants (Hunt, 1949;
Stewart, 1957). However, MB has been
implicated in the depletion of the ozone
layer (UNEP, 2000) and is therefore now
restricted to quarantine situations and a few
agricultural commodities (Potter, 2011). In
2013 only SF (three registrants) was
registered as a structural fumigant in the
USA. Chloropicrin, also a fumigant, is only
used as a warning agent to discourage
human re-entry into fumigated structures
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