9.2.3 Host Associations, Parasitoid Assemblages
In many cases, exact identification of the aphidiinae parasitoids is not possible
without host data, both aphid and its host plant. There are many aphidiinae species
described without host data (Rakhshani et al. 2012c; Davidian 2016), but further
identification would need comparison with the type specimens. Data about host
associations greatly helps by search through a narrow assemblage of species and
generally gives more reliable identification. Based on these requirements, many
researchers tried to work on the reared material, which their host aphids and plants
are already identified. Aphids are group of insects with mostly very simple rearing
methods and their colonies consisting parasitized individuals can be easily kept
inside the plastic boxes at room temperature. In order to increase the rate of
parasitoid emergence, it is recommended to remove all other insects, which are
associated with the same plant material. It is critically important with the predators
like coccinellids, chrysopids, anthocorids, etc. Ignoring other insects can also have
led to emergence of the parasitoid species, which were incorrectly assigned as aphid
parasitoids (see Samanta et al. 1983). Many aphid species occur on the same host
plant and at same time with mixed or overlapped colonies. Rearing the mixed aphid
colonies result to incorrect host association records (see Jafari and Modarres Awal
2012).
The pattern of host specificity was preliminarily classified based on their host
aphid phylogeny (Starý 1981), by which five subgroups were defined. It ranges from
the parasitoids associated with single host aphid species to those parasitizing the
species from several genera in two or more aphid subfamilies. In the recent most
comprehensive analysis, Žikić et al. (2017) suggested three groups including specialists, generalist and oligophagous species. The latter group was also subdivided
into three subgroups of narrow, moderate and broad oligophagous species.
The aphids occur on various host plants, both in natural and agro-ecosystems
manifesting a heterogeneous parasitoid complex of different genera (Rakhshani et al.
2005a, 2007b, 2011). On the other hand, there are aphids with only a single
parasitoid species or even without parasitoids, at least in Iran and adjacent countries.
Some parasitoid species can be found in the colonies of many common aphids in
ago-ecosystems and their nearby areas, which have a great potential to shift their host
aphid, when the environments is changing. In general, it is important to have the
parasitoid species with a narrow and preferably single host specific behavior in
biological control programs. It is expected that the specific parasitoids are more
successful in control of their host aphid, since they will not disperse around on the
other non-target host aphids. In such a way, the environmental risk of ecological
interference can also be minimized. Surprisingly, the important parasitoid species are
seldom host specific, especially those are commercially produced. Among them,
Lysiphlebus testaceipes is known as a parasitoid with unbelievably wide host range
pattern (Starý et al. 2004). It was found occasionally in Iran, reared from Aphis
craccivora (Rakhshani et al. 2005a), but never recovered again. It could be an
occasional application of commercially reared specimens by the local peoples or
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339
In many cases, exact identification of the aphidiinae parasitoids is not possible
without host data, both aphid and its host plant. There are many aphidiinae species
described without host data (Rakhshani et al. 2012c; Davidian 2016), but further
identification would need comparison with the type specimens. Data about host
associations greatly helps by search through a narrow assemblage of species and
generally gives more reliable identification. Based on these requirements, many
researchers tried to work on the reared material, which their host aphids and plants
are already identified. Aphids are group of insects with mostly very simple rearing
methods and their colonies consisting parasitized individuals can be easily kept
inside the plastic boxes at room temperature. In order to increase the rate of
parasitoid emergence, it is recommended to remove all other insects, which are
associated with the same plant material. It is critically important with the predators
like coccinellids, chrysopids, anthocorids, etc. Ignoring other insects can also have
led to emergence of the parasitoid species, which were incorrectly assigned as aphid
parasitoids (see Samanta et al. 1983). Many aphid species occur on the same host
plant and at same time with mixed or overlapped colonies. Rearing the mixed aphid
colonies result to incorrect host association records (see Jafari and Modarres Awal
2012).
The pattern of host specificity was preliminarily classified based on their host
aphid phylogeny (Starý 1981), by which five subgroups were defined. It ranges from
the parasitoids associated with single host aphid species to those parasitizing the
species from several genera in two or more aphid subfamilies. In the recent most
comprehensive analysis, Žikić et al. (2017) suggested three groups including specialists, generalist and oligophagous species. The latter group was also subdivided
into three subgroups of narrow, moderate and broad oligophagous species.
The aphids occur on various host plants, both in natural and agro-ecosystems
manifesting a heterogeneous parasitoid complex of different genera (Rakhshani et al.
2005a, 2007b, 2011). On the other hand, there are aphids with only a single
parasitoid species or even without parasitoids, at least in Iran and adjacent countries.
Some parasitoid species can be found in the colonies of many common aphids in
ago-ecosystems and their nearby areas, which have a great potential to shift their host
aphid, when the environments is changing. In general, it is important to have the
parasitoid species with a narrow and preferably single host specific behavior in
biological control programs. It is expected that the specific parasitoids are more
successful in control of their host aphid, since they will not disperse around on the
other non-target host aphids. In such a way, the environmental risk of ecological
interference can also be minimized. Surprisingly, the important parasitoid species are
seldom host specific, especially those are commercially produced. Among them,
Lysiphlebus testaceipes is known as a parasitoid with unbelievably wide host range
pattern (Starý et al. 2004). It was found occasionally in Iran, reared from Aphis
craccivora (Rakhshani et al. 2005a), but never recovered again. It could be an
occasional application of commercially reared specimens by the local peoples or
9 Aphid Parasitoids: Aphidiinae (Hym., Braconidae)
339