necessary to investigate the capacity of aphid parasitoids in suppressing aphid
populations under field conditions (Khajehzadeh et al. 2010), as well as surveys
targeting to find how to manipulate the habitats for achieving the highest rate of
parasitism and survival of the parasitoids.
9.3.2 Reproduction and Life Table Statistics
Among the natural enemies of a given pest aphid, those with greater specific
association have higher priority in biological control programs. In the basic theory,
the parasitoids have to combat against continuous impacts of the adverse environments even in their native area. So, they should acquire enough natural capacity to
compensate mortalities and to establish the next generation. Rate of reproduction is
the key element, which is closely connected to the survival of the populations
through long term adaptations. Two non-equal terms fertility and fecundity are
used for assessing the potential of growth rate in population of both pests and their
natural enemies (Jervis and Kidd 1996). The reproduction of natural enemies
generally defined with a statistical parameter known as “Intrinsic rate of increase
¼ r” which is assessing in a set of laboratory conditions. Wide range of laboratory
setup and analytical method are commonly used (Carey 1993; Chi and Su 2006) for
the life table construction of the natural enemies including the aphid parasitoids. The
various parameters within the life table statistics are the simple translation of a
complicated reproductive strategy, including host selection, competition, rate of
oviposition, survival, superparasitism, developmental time, sex ratio, mutual interference etc., which affects the fitness and dynamics of the host–parasitoid interactions (Roitberg et al. 2001). The intrinsic rate of increase of a parasitoid related to its
hosts play an important role in biological control programs (Khatri et al. 2017).
Parasitoids with the greatest value for the intrinsic rate of natural increase are
obviously better candidates in biological control program. At the same way, it is
very important that the selected parasitoid has a greater value comparing its host
aphid (Bigler 1989).
The progeny sex ratio as main factor among the life table statistics, also affects the
stability of the host parasitoid interactions and rate of controlling efficiency for the
aphid parasitoids, and other natural enemies, as well. Various parameters including
host aphid (Mackauer and Kambhampati 1988a; Pandey and Singh 1999; Jarosik
et al. 2003; Kairo and Murphy 2005; Sidney et al. 2011), temperature (Pandey and
Singh 1998; Singh et al. 2000; Zamani et al. 2007, 2012; Tazerouni et al. 2012b;
Silva et al. 2015), intraspecific competition (Mackauer and Völkl 2002; West, 2009),
and maternal effects (Hofsvang and Hägvar 1975; Godfray 1994), significantly
affect the progeny sex ratio and life history parameters of the aphid parasitoids.
Virgin female produce only male offspring, a phenomenon that frequently happened
in the mass rearing and also in the aged females (Talebi et al. 2002; Sequeira and
Mackauer 1993; Chi and Su 2006). Reproduction is a high temperature dependent
9 Aphid Parasitoids: Aphidiinae (Hym., Braconidae)
345
populations under field conditions (Khajehzadeh et al. 2010), as well as surveys
targeting to find how to manipulate the habitats for achieving the highest rate of
parasitism and survival of the parasitoids.
9.3.2 Reproduction and Life Table Statistics
Among the natural enemies of a given pest aphid, those with greater specific
association have higher priority in biological control programs. In the basic theory,
the parasitoids have to combat against continuous impacts of the adverse environments even in their native area. So, they should acquire enough natural capacity to
compensate mortalities and to establish the next generation. Rate of reproduction is
the key element, which is closely connected to the survival of the populations
through long term adaptations. Two non-equal terms fertility and fecundity are
used for assessing the potential of growth rate in population of both pests and their
natural enemies (Jervis and Kidd 1996). The reproduction of natural enemies
generally defined with a statistical parameter known as “Intrinsic rate of increase
¼ r” which is assessing in a set of laboratory conditions. Wide range of laboratory
setup and analytical method are commonly used (Carey 1993; Chi and Su 2006) for
the life table construction of the natural enemies including the aphid parasitoids. The
various parameters within the life table statistics are the simple translation of a
complicated reproductive strategy, including host selection, competition, rate of
oviposition, survival, superparasitism, developmental time, sex ratio, mutual interference etc., which affects the fitness and dynamics of the host–parasitoid interactions (Roitberg et al. 2001). The intrinsic rate of increase of a parasitoid related to its
hosts play an important role in biological control programs (Khatri et al. 2017).
Parasitoids with the greatest value for the intrinsic rate of natural increase are
obviously better candidates in biological control program. At the same way, it is
very important that the selected parasitoid has a greater value comparing its host
aphid (Bigler 1989).
The progeny sex ratio as main factor among the life table statistics, also affects the
stability of the host parasitoid interactions and rate of controlling efficiency for the
aphid parasitoids, and other natural enemies, as well. Various parameters including
host aphid (Mackauer and Kambhampati 1988a; Pandey and Singh 1999; Jarosik
et al. 2003; Kairo and Murphy 2005; Sidney et al. 2011), temperature (Pandey and
Singh 1998; Singh et al. 2000; Zamani et al. 2007, 2012; Tazerouni et al. 2012b;
Silva et al. 2015), intraspecific competition (Mackauer and Völkl 2002; West, 2009),
and maternal effects (Hofsvang and Hägvar 1975; Godfray 1994), significantly
affect the progeny sex ratio and life history parameters of the aphid parasitoids.
Virgin female produce only male offspring, a phenomenon that frequently happened
in the mass rearing and also in the aged females (Talebi et al. 2002; Sequeira and
Mackauer 1993; Chi and Su 2006). Reproduction is a high temperature dependent
9 Aphid Parasitoids: Aphidiinae (Hym., Braconidae)
345