common conservation efforts. The plant habitat manipulations (Fiedler et al. 2008)
including production of nectars (Zhao et al. 1992), attractiveness to natural enemies
(Patt et al. 1997) and phenology of the flowering period (Rebek et al. 2005) have
direct impact on the parasitoids. The objective of conservation programs is to ensure
about proper occurrence of the parasitoid with its resource requisites including the
preferred host, so maximizing plant species diversity may accomplish the matter in
its own way. The complexity of the plant community, as an element of the sustainable agriculture may has benefits for both specialist and generalist aphid parasitoids,
providing the shelter and protect them against hyperparasitoids and extreme weather
conditions. The situation is different in the case of broadly oligophagous aphid
parasitoids, which has different host aphids in various habitats (Barbosa and Benrey
1998). The result of an experimental survey on the rate of complexity and its effect
on conservation biological control (Jonsson et al. 2015) suggested that conservation
programs are most effective in moderately simple agricultural landscapes, and less
effective in either very simple (no capacity for response), or in highly complex
landscapes (already saturated in responses). In general, the effect of plant diversity
on the efficiency of conservation biological control is complicated, since the host
aphid may also benefit from the same modifications. Inter-cropping and other
practices that increase the plant species diversity bring further modification both
on intraguild predations, as well as hyperparasitism that is hard to find a clear
assessment. The hydrocarbon resources including nectars can be supplied by the
various flowering plants in surrounding area. Effect of hyperparasitism has generally
been ignored in the context of conservation biological control (Polis and Winemiller
1996). The surveys by Araj et al. (2011) indicated the searching efficiency of
primary and secondary parasitoids of Acyrthosiphon pisum was enhanced, when
accessing floral nectar. They concluded that nectar provision can potentially have
positive or negative effects, depending on the relative proportion of each species.
Various plants of the same or different family supporting the host aphids of the
parasitoid, which primarily attacking the pest aphid. Further details about reservoir
host plants in the field conditions, and in similar way to the “banker plants” in the
greenhouse are presented in previous section. Surprisingly that is an important
aspect of conservation program for biological control of the pest aphids (Brown
and Mathews 2007) with the same definition of increase in plant diversity. No need
for additional efforts in plantation of these plants in many cases, since they are
growing naturally, around or inside the arable crops and especially in fruit orchards.
The continuous application of the chemical insecticides in large scale caused
many environmental and ecological problems including development of resistance
in serious pest aphids (Ghadamyari et al. 2008) and subsequent resurgence of their
populations in the absence of their natural enemies which destroyed by the direct and
indirect effects of the pesticides (Hardin et al. 1995). The lethal and sub-lethal effects
of insecticides on the aphid parasitoids can be reduced in different ways, mainly by
decreasing the doses and frequency of applications. Achieving the ecological selectivity by timing treatments is likely to be impractical within the current situation of
agriculture in many parts of Iran. Simultaneously, problems with the other key pests
are the major reason prohibiting the scheduled treatments for the aphids, when their
9 Aphid Parasitoids: Aphidiinae (Hym., Braconidae)
375
including production of nectars (Zhao et al. 1992), attractiveness to natural enemies
(Patt et al. 1997) and phenology of the flowering period (Rebek et al. 2005) have
direct impact on the parasitoids. The objective of conservation programs is to ensure
about proper occurrence of the parasitoid with its resource requisites including the
preferred host, so maximizing plant species diversity may accomplish the matter in
its own way. The complexity of the plant community, as an element of the sustainable agriculture may has benefits for both specialist and generalist aphid parasitoids,
providing the shelter and protect them against hyperparasitoids and extreme weather
conditions. The situation is different in the case of broadly oligophagous aphid
parasitoids, which has different host aphids in various habitats (Barbosa and Benrey
1998). The result of an experimental survey on the rate of complexity and its effect
on conservation biological control (Jonsson et al. 2015) suggested that conservation
programs are most effective in moderately simple agricultural landscapes, and less
effective in either very simple (no capacity for response), or in highly complex
landscapes (already saturated in responses). In general, the effect of plant diversity
on the efficiency of conservation biological control is complicated, since the host
aphid may also benefit from the same modifications. Inter-cropping and other
practices that increase the plant species diversity bring further modification both
on intraguild predations, as well as hyperparasitism that is hard to find a clear
assessment. The hydrocarbon resources including nectars can be supplied by the
various flowering plants in surrounding area. Effect of hyperparasitism has generally
been ignored in the context of conservation biological control (Polis and Winemiller
1996). The surveys by Araj et al. (2011) indicated the searching efficiency of
primary and secondary parasitoids of Acyrthosiphon pisum was enhanced, when
accessing floral nectar. They concluded that nectar provision can potentially have
positive or negative effects, depending on the relative proportion of each species.
Various plants of the same or different family supporting the host aphids of the
parasitoid, which primarily attacking the pest aphid. Further details about reservoir
host plants in the field conditions, and in similar way to the “banker plants” in the
greenhouse are presented in previous section. Surprisingly that is an important
aspect of conservation program for biological control of the pest aphids (Brown
and Mathews 2007) with the same definition of increase in plant diversity. No need
for additional efforts in plantation of these plants in many cases, since they are
growing naturally, around or inside the arable crops and especially in fruit orchards.
The continuous application of the chemical insecticides in large scale caused
many environmental and ecological problems including development of resistance
in serious pest aphids (Ghadamyari et al. 2008) and subsequent resurgence of their
populations in the absence of their natural enemies which destroyed by the direct and
indirect effects of the pesticides (Hardin et al. 1995). The lethal and sub-lethal effects
of insecticides on the aphid parasitoids can be reduced in different ways, mainly by
decreasing the doses and frequency of applications. Achieving the ecological selectivity by timing treatments is likely to be impractical within the current situation of
agriculture in many parts of Iran. Simultaneously, problems with the other key pests
are the major reason prohibiting the scheduled treatments for the aphids, when their
9 Aphid Parasitoids: Aphidiinae (Hym., Braconidae)
375