International Journal of Horticulture 2015, Vol.5, No.4, 1
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digestion or absorption in their metabolic process.
Thus, all the instars including adults were efficiently
converting
S. pinnata
leaf tissues into their biomass by
homeostatic adjustment in consumption rates and
other efficiency parameters of the insect for ideal
growth and development (Roy and Barik, 2012; 2013).
The food utilization indices ultimately influence
developmental duration, adult longevity, fecundity and
survival of
P. quatuordecimpunctata
during their
developmental stages like duration of growth and
reproduction. Adult emergence was significantly
higher on
S. pinnata
leaves (39.12±1.91%) relative to
S. dulcis
leaves (28.42±1.29%) (Figure 2). High
survival rates and shorter developmental time of
P.
quatuordecimpunctata
on
S. pinnata
indicates better
nutritional quality of their leaves larval food (Slansky
and Scriber, 1985). These results of this study are also
in good agreement with the previous work (Roy and
Barik, 2013) when they were reared on
S. pinnata
and
S. dulcis
leaves. Furthermore, the growth index (GI)
and feeding index (FI) was higher on
S. pinnata
leaves
than
S. dulcis
(Figure 4) due to higher adult
emergence (Figure 2) with respect to shorter
developmental period. Therefore, it can be concluded
that
S. pinnata
leaves provides the best quality food
for their better nutritional ecology including feeding,
growth and development of the leaf beetle,
P.
quatuordecimpunctata
, because of higher nutritional
factors relative to the anti-nutritional secondary
metabolites.
Life table study is a central theme in ecological
research and used to calculate the vital statistics on
pest population dynamics including comprehensive
description of the survivorship, development,
fecundity, mortality and life expectancy (Southwood,
1978; Carey, 2001; Sarfraz et al., 2007; Ali and Rizvi,
2008). Life table is widely useful technique in insect
pest management, where developmental stages are
discrete and mortality rates vary widely from one life
stage to another (Kakde et al., 2014). There is a range
of innet capacity for individual of a population (Gill et
al., 1989) but the variation in available food quality
(Kim and Lee, 2002; Liu et al., 2004; Yasar and
Güngör, 2005; Win et al., 2011; Roy and Barik, 2013)
along with environmental factors (Ellers-Kirk and
Fleischer, 2006; Schowater, 2006; Ali and Rizvi, 2010)
always influence the growth, reproduction, longevity
and survival of that population. The effect of different
food sources on population parameters were observed
in
Plutella xylostella
(Sarfraz et al
.
, 2007),
Earias
vitella
(Satpute et al., 2005) and
D. casignetum
(Roy
and Barik, 2013) on different host plants. Variation
between the results of this study could be attributed to
differences among nutritional and anti-nutritional
factors present in the respective hog-plum leaves that
directly affect potential and achieved herbivore
development and fecundity (Awmack and Leather,
2002; Syed and Abro, 2003; Roy and Barik, 2013).
The overall accumulated survival rate of
P.
quatuordecimpunctata
on
S. pinnata
leaves was
highest as compared with that on
S. dulcis
leaves and
the result suggest type III survival curve (Figure 2)
like most insect species (Price, 1998; Schowalter,
2006). The R
0
, r
m
and T
c
are fundamental ecological
parameters to predict the pest population growth to
evaluate the performance of an insect on different host
plants as well as the host plant's resistance
(Southwood and Henderson, 2000; Win et al., 2011).
In the present study, T
c
of
P. quatuordecimpunctata
was significantly shorter on
S. pinnata
leaves compare
to
S. dulcis
. Whereas, the R
0
was also significantly
differed but higher on
S. pinnata
than on
S. dulcis
leaves (Table 9). Thus, the population parameters of
P.
quatuordecimpunctata
on
S. pinnata
and
S. dulcis
leaves will help to assess the relative contribution
made by the respective leaf constituents to the adult
population pool.
In respect to the phytochemical regime,
S. pinnata
leaves had the lowest antibiosis resistance against
P.
quatuordecimpunctata
and were the most favorable
one relative to
S. dulcis
as indicated by the short
developmental time, which leads to reduce exposure
of the insect to its natural enemies, and high survival
of immature stages. Such reduced antibiosis effects of
S. pinnata
leaves relative to
S. dulcis
could cause
increase in survival fitness of
P. quatuordecimpunctata
which can help one to determine the key mortality
factors responsible in a particular stage within which
the maximum mortality of the pest is obtained. By
knowing such most vulnerable stages from life table,
one can also make time based application of different
control measures for proper management of that pest
population. Other than the phytochemical regime,
S.
pinnata
leaves are much larger (5-8 times) than
S.
dulcis
which support the poor dispersal ability of
P.
quatuordecimpunctata
larvae and adults. Even,
S.
dulcis
fruiting season also co-inside with the time for
