Biology Reference
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Table 15.6.
Growth index (GI) and relative growth index (RGI) of
Spodoptera frugiperda
as a function of
increased concentrations of extracts from
Calceolaria talcana
a
Compounds
Concentration (ppm)
GI
b
RGI
c
Control
0.95 ± 0.02a
1.0
Hexane
10.0
0.94 ± 0.12b
0.99
20.0
0.93 ± 0.09b
0.98
35.0
0.91 ± 0.08c
0.96
50.0
0.71 ± 0.07d
0.75
Ethyl acetate
10.0
0.71 ± 0.08d
0.75
20.0
0.41 ± 0.08e
0.45
35.0
0.28 ± 0.05f
0.29
Methanol
10.0
0.93 ± 0.03b
0.98
20.0
0.83 ± 0.08g
0.87
35.0
0.69 ± 0.04d
0.73
50.0
0.28 ± 0.04f
0.29
Verbascoside
10.0
0.66 ± 0.05h
0.67
25.0
0.41 ± 0.03e
0.45
35.0
0.09 ± 0.01i
0.15
50.0
0.07 ± 0.01i
0.10
Gedunin
d
10.0
0.77 ± 0.06d
0.71
25.0
0.51 ± 0.04j
0.55
50.0
0.10 ± 0.01k
0.11
a
Mean of three replicates.
b
Means followed by the same letter within a column after ± standard error values are not
significantly different in a Student-Newman-Keuls (SNK) test at
p
<0.05 (treatments are compared by concentration to
control), 95% confidence limits.
c
RGI
treatment
= GI
treated
/ GI
control
.
d
Data shown for gedunin are identical to those reported in
Torres
et al.
(2003).
Interestingly, the most probable phyto-
chemical composition of the active extracts
of this study could be diterpenes, flavo-
noids, phenylethanoids, phenylpropa-
noids and iridoids (Di Fabio
et al.
, 1995;
Garbarino
et al.
, 2000). Because these
extracts have activity on moulting pro-
cesses, it is possible that they can act in a
similar manner to structures such as ecdys-
teroids. Its action is similar to juvenile
hormone mimics that occur in higher
plants. These extracts from Calceolariaceae
species have similar activity to known
juvenile hormone mimics but do not have
the same structure composition. Insect
growth regulatory activity on
S. frugiperda
was shown by phytoecdysteroids from
Ajuga remota
(Labiatae) (Kubo
et al.
, 1981)
on two polyphagous (
Spodoptera littoralis
and
Ostrinia nubilalis
) and a monophagous
(
Bombyx mori
) species (Marion-Poll and
Descoins, 2002). Similar activities have
been shown by ponasterone A, B and C
and 20E, inokosterone and other terpenes
that have been isolated from
Podocarpus
nakaii
(Nakanishi
et al.
, 1966), from
P. elatus
(Galbraith and Horn, 1966), and from
P. nagi
and
P. gracilior
(Kubo
et al.
, 1993).
Although there is an ample body of lit-
erature about biological activities of phyto-
ecdysteroids (Schmelz
et al.
, 1999; Dinan,
2001; Dinan
et al.
, 2001), there are no reports
about insecticidal activity of any type of
extracts from Calceolariaceae species; the
only report about insecticidal activity from
one
Calceolaria
is the insecticidal activity
of a naphtoquinone isolated from
C. andina
(Khambay
et al.
, 1999).
15.5.8
Acute toxicity on last-stage
larvae of
S. frugiperda
To determine a possible correlation between
IGR, acute toxicity and ecdysis caused by active
extracts and verbascoside, the oral injection of
25 mg/ml of all samples into ten larvae (21 days
old) of
S. frugiperda
was carried out. This con-
centration promoted apolysis to the fifth instar,
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