Agriculture Reference
In-Depth Information
is relatively low, their attractiveness may
encourage the transfer of bait toxicants to
other members resting within the harbour-
age.
43% of adult
P. fuliginosa
were cannibalized
when they were reared with only faeces and
water.
Differences in the mode of action of
active ingredients in various baits also
explain the differences in translocation of
baits through cannibalism. Durier and
Rivault (2000c) found that cannibalism of
cadavers intoxicated with fi pronil bait by
German cockroaches was low (3.55%),
whereas it was higher (12.1%) in the
hydramethylnon bait treatment. Neverthe-
less, the resultant mortality was higher in
the fi pronil (47.3%) treatment than in the
hydramethylnon (29.7%) treatment. This
suggests that fi pronil, which functions
through ingestion and contact, may work
well even with a low cannibalism rate,
whereas hydramethylnon is less effi cient
because it is less toxic by contact than by
ingestion. In another study, le Patourel
(2000) demonstrated that cadavers of
Blatta
orientalis
intoxicated with 0.05% fi pronil
bait still managed to result in ≥ 64%
secondary mortality via cannibalism among
adult females.
Cannibalism
Cannibalism occurs in cockroaches during
laboratory rearing and during experimental
testing as observed by Gahlhoff
et al
. (1999),
Durier and Rivault (2000c), le Patourel
(2000), Tabaru and Watabe (2003) and
Tabaru
et al
. (2003). The degree of cannibal-
ism depends on the quantity and quality of
food and also the population density of the
cockroach (Bell
et al
., 2007), and is most
prominent when cockroaches are deprived
of food (Appel
et al
., 2008). It is often
directed toward individuals that are newly
hatched or moulted, injured or weak
(Cornwell, 1968). Cannibalism may also be
an adaptive behaviour because it allows
adjustment of population density, con-
centrates the resources into groups that
have higher potential of survivorship and
acts as a sanitary practice that prevents the
spreading of disease pathogens (Ross and
Mullins, 1995; Bell
et al
., 2007). A relatively
large amount of ingested bait tends to
remain within the dead body (Silverman
et
al
., 1991; Buczkowski and Schal, 2001b).
Therefore, cannibalism in cockroaches is
one mechanism by which bait toxicants are
disseminated to healthy conspecifi cs and its
effect is infl uenced by food availability, life
stage of the bait-fed donor and type of
insecticide used (Appel
et al
., 2008; Wang
et al
., 2008).
In the presence of food, Appel
et al
.
(2008) reported that
B. germanica
males
preferred dog food to cadavers of nymphs
and adult males. Thus, no mortality of
B.
germanica
males occurred in treatments
containing cadavers of bait-fed conspecifi cs.
Cannibalism was most prominent when
males were denied access to food during a
test period of 14 days. This indicates that
cockroaches may rely on body reserves
during periods of starvation and opt for
cannibalism when food is not available.
Tabaru and Watabe (2003) reported that
Factors Affecting Bait Performance in
the Field
Sanitation of the treatment area
Cockroaches fi nd suitable harbourage close
to food and water (Ross
et al
., 1984). Several
studies reported that poor sanitation is
positively correlated to cockroach infest-
ation level (Wright, 1979; Schal, 1988),
whereas a few others contradicted (Gold,
1995; Lee and Lee, 2000a). In a fi eld
evaluation, Lee and Lee (2000b) found that
cockroach bait reduced the cockroach popu-
lation faster in houses with good sanitation
compared to those with poor sanitation.
Moreover, the reduction in well-sanitized
houses could be sustained for up to 12
weeks, whereas it was only 6 weeks for
those with poor sanitation. In low-income
houses and apartments, higher numbers of
baits were also required to reduce the
cockroach population compared to resi-
dences with good sanitation (Lee and
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