Management of Drywood Termites: Past Practices, Present Situation and Future Prospects - Urban Insect Pests: Sustainable Management Strategies - page 140

preservatives to wood included total sub-
mersion in dip tanks or pressure treatment
under vacuum in metal retorts. During the
1920-1930s, dozens of additional active
ingredients were also tested for use as wood
preservatives against subterranean termites
and decay with drywood termites listed as
an afterthought (Randall and Doody, 1934b).
Wagner and Ebeling (1959) listed 162
insecticidal dust formulations that were
tested for their potential to prevent drywood
termite infestations. Their recommendation
was to use silica gel dusted into attics as a
post-construction prevention measure, not
as a pre-construction recommendation
(Wagner and Ebeling, 1959). Other active
ingredients used as wood preservatives for
new and post-construction treatments
included: creosote, copper naphthenate,
pentachlorophenol and chromated copper
arsenate (CCA) (Randall and Doody, 1934b;
Mallis, 1945; Hunt, 1949; Snyder, 1950).
Resistant species of wood (for example, old
growth redwood, Sequoia ) were also widely
recommended (Brown et al ., 1934; Randall
et al. , 1934a; Scheffrahn, 1991; Potter, 2011).
Currently, modern wood preservatives
can be characterized into fi ve groups: con-
taining boron, CCA (restricted use and being
phased out), dissolved copper-based (pri-
mary replacements for CCA), copper sus-
pension-based (micronized or fi nely ground
copper particles suspended in water) and
carbon-based (containing little or no metals)
(Gentz and Grace, 2006; Cushman, 2009;
Ismayati, et al ., 2011). The mode of action of
boron includes the rapid esterifi cation of
borates with molecules of biological signifi -
cance (Gentz and Grace, 2006), for copper-
based preservatives the oxidizing of
proteins, enzymes and lipids (Freeman and
McIntyre, 2008) and for products containing
imidacloprid, a nerve poison that affects the
acetylcholine binding sites called nico-
tinergic receptors (Ramakrishnan et al .,
2000). By some estimates, the use of wood
preservatives is 75% of the total poundage
of pesticides used in North America
(Freeman, 2003).
Studies that examine the potential for
prevention of drywood termite infestations
have been few in the current century,

whereas increased regulatory concerns over
safety and negative environmental effects
have drawn increased scrutiny of wood
preservatives (Freeman et al. , 2003). A
novel series of studies were conducted
where treated wooden blocks and simulated
attic modules were exposed to swarms from
infested doors containing active C. brevis
infestations; the alates were permitted to
search for sites to initiate incipient colonies
(Scheffrahn et al ., 1998, 2001). The results
of these investigations legitimized and
supported the use of six, currently available,
wood preservatives applied as topical
treatments to prevent the establishment of
new drywood termite colonies. These active
ingredients included: 10% amorphous
silica gel dust with synergized 1%
pyrethrins and 10% piperonyl butoxide;
CCA; disodium octaborate tetrahydrate
(DOT) liquid and dust; imidacloprid dust;
and spinosad suspension concentrate.
Another study directed at I. minor in Japan
used two alkylammonium compounds,
didecyldimethylammonium tetrafl uorobor-
ate (DBF) and didecyldimethylammonium
chloride (DDAC), and also supported their
use as a preventative intervention (Hwang
et al. , 2006). Products that include dissolved
copper-based, copper suspension-based and
carbon and organo-complex active ingredi-
ents and formulations have been reported
(Cushman, 2009), but little has been pub-
lished on the success of these 'replacement'
wood preservatives in preventing drywood
termite infestations.
Little is known from laboratory or fi eld
studies on how non-cellulose materials,
screens, caulks and paints prevent the
establishment of drywood termite infest-
ations (Brown et al ., 1934; Randall et al. ,
1934c; Mallis, 1945; Rust and Scheffrahn,
1982; Su and Scheffrahn, 1990, 2000).

Challenges to Consistent, Verifi able
Drywood Termite Management

Management of drywood termites is diffi cult
for a number of reasons including the
cryptic nature of the insect and a biology
that involves survival in xeric habitats,