Sustainable Cockroach Management Using Insecticidal Baits: Formulations, Behavioural Responses and Issues - Urban Insect Pests: Sustainable Management Strategies - page 79

(Lee and Soo, 2002b). However, substitution
of glucose with fructose increased bait
effi cacy against glucose-averse B. germanica
(Silverman and Bieman, 1993; Silverman
and Ross, 1994). There are associative costs
in glucose-averse B. germanica , in that they
have smaller and fewer numbers of eggs in
oothecae and, if fed diets supplemented
with glucose, they have lower population
growth rates than non-averse cockroaches.
This fi tness cost gives them an advantage,
however, in environments implemented
with cockroach baiting (Silverman, 1995;
Wang et al ., 2004).
Wada-Katsumata et al . (2013) described
the chemosensory mechanism responsible
for glucose aversion in B. germanica . The
authors reported that glucose stimulated
responses on sugar-gustatory receptor
neurons in both averse and non-averse
cockroaches. However, glucose also induced
responses on bitter-gustatory neurons in
glucose-averse cockroaches, and this over-
rode the responses stimulated by sugar-
gustatory neurons. They hypothesized that
one or more mutations may have resulted in
changes in the structure of gustatory recep-
tors on bitter-gustatory neurons to accept
glucose.
A decade later, Wang et al . (2004)
reported that German cockroaches exhibited
aversion to multiple sugar compounds
(glucose, fructose, sucrose and maltose) in
some fi eld cockroach populations. This
discovery, however, was disputed by
Silverman (2005) on the basis that it is
unlikely that independent mutations for
each sugar could all occur at the same time.
Lee (2007) speculated that bait aversion in
the German cockroach may not be due to
aversion to the sugar compound but instead

to aversion to one (or more) components
used in the bait formulation. Bait manu-
facturers have since produced gel bait
formulations that can overcome bait-averse
German cockroaches.

Conclusion

Improvements in bait technology and the
availability of novel toxicants suitable for
incorporation into baits have contributed to
the effi cacy of cockroach baits, which in
turn has led to the popularity and great
acceptance of cockroach baiting. Neverthe-
less, the potential of baits can only be
maximized when information about the
biology and behaviour of pest cockroaches
is used in the baiting programme. Foraging
strategies of cockroaches greatly infl uence
where bait should be placed in the
cockroach environment. Placement of bait
that disrupts the familiar environment of
cockroaches may result in lower acceptance
of bait. In addition, the nutritional require-
ments and foraging effi ciency of each life
stage require that bait be long lasting and
placed as close as possible to all the
identifi ed harbourage sites. The importance
of sanitation cannot be neglected because it
can create an environment that promotes
cockroach exploratory behaviour, which
increases the likelihood of the cockroaches
coming in contact with the bait and
enhances the effects of horizontal trans-
mission. Lastly, the strong adaptive behav-
iour of cockroaches, as demonstrated by the
incidence of bait aversion, and the prolifer-
ative nature of B. germanica will continue
to make cockroach management using toxic
bait challenging.

References

Ang, L.H., Nazni, W.A., Kuah, M.K., Shu-Chien, A.C. and Lee, C.Y. (2013) Detection of the A302S Rdl
mutation in fi pronil-selected strains of the German cockroach, Blattella germanica (L.) (Dictyoptera:
Blattellidae). Journal of Economic Entomology 106, 2167-2176.
Appel, A.G. (1990) Laboratory and fi eld performance of consumer bait products for German cockroach
(Dictyoptera: Blattellidae) control. Journal of Economic Entomology 83, 153-159.
Appel, A.G. (1992) Performance of gel and paste baits for German cockroach (Dictyoptera: Blattellidae)
control: laboratory and fi eld studies. Journal of Economic Entomology 85, 1176-1183.