major parts of parasitoid populations are in pupal stage within the mummified aphids
(Newsom et al. 1976). Even at this situation, the sub-lethal effects on the emerging
adults can be detrimental (Desneux et al. 2006; Sabahi et al. 2011; Purhematy et al.
2013; Mardani et al. 2016). Mortality of the emerging parasitoids was observed in
the case of treatment by dimethoate or deltamethrin and has assumed caused by
ingestion of insecticide residues, when the adult parasitoid was trying to cut a hole in
the mummy with its mandibles (Polgar and Sagi 1983). Aphids in alfalfa fields of
Iran have a complex of efficient parasitoids (Rakhshani et al. 2006a), which occasionally help in biocontrol of the aphids in neighbouring fields, too. Normally no
chemical treatments are needed for alfalfa even at the period of outbreak in population of its key pest, Hypera postica (Gyllenhal). It has also been strongly
prohibited because of foraging value for the livestock. Occasional application of
chemical insecticide directly reflecting the emergence of large aphid populations
represented by Acyrthosiphon pisum (Harris).
The adult parasitoid leaves the treated patches and avoid oviposition in these
areas (Longley and Jepson 1996). The catastrophic aphid mortality following insecticide treatment can also result migration of the parasitoids to the nearby areas, where
they may fail to find suitable food resources. This phenomena is quite common in
isolated monocultures and cause a longer delay in establishing the new generation of
the parasitoids on the growing population of the survived aphids. Organic farming is
an alternative to the conventionally managed farms, in which a higher proportion of
semi-natural habitat are exist (Langer 2001). Inter-cropping as a model that enhances
the plants diversity (Gibson et al. 2007) and the pesticide application is prohibited
(Lampkin 1999) to improve colonization of aphid parasitoids. Within such environment, pest control process is naturally occurring by the same predators and parasitoids, but very efficiently in absence of the insecticides. Presence of alternate aphid
hosts, as well as food resources for the adult parasitoids enhance their efficiency in a
complex organic farming system (Langer 2001; Macfadyen et al. 2009).
9.6 Conservation of the Aphid Parasitoids
9.6.1 Concept of Refugiums for the Aphid Parasitoids
The term “refugia” has been originally used for a site or area where some rare/
endangered species have succeeded to survive. It has been used for the endemic
species, “living relics”, and potentially also for rare species which required conservation and environmental protection. In this respect, the meaning still has been
respectively used. However, diversification of the landscape and namely, the development of agroecosystems has determined some situations, where the pests as well
as useful natural enemies are concentrated and/or surviving after unfavourable
periods of the season, and may again re-expand in the environment. In the natural
plant community conservation programmes, it is easy to join it with the aphid and
parasitoids associations, as each aphid and a parasitoid is generally capable to find a
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E. Rakhshani and P. Starý
(Newsom et al. 1976). Even at this situation, the sub-lethal effects on the emerging
adults can be detrimental (Desneux et al. 2006; Sabahi et al. 2011; Purhematy et al.
2013; Mardani et al. 2016). Mortality of the emerging parasitoids was observed in
the case of treatment by dimethoate or deltamethrin and has assumed caused by
ingestion of insecticide residues, when the adult parasitoid was trying to cut a hole in
the mummy with its mandibles (Polgar and Sagi 1983). Aphids in alfalfa fields of
Iran have a complex of efficient parasitoids (Rakhshani et al. 2006a), which occasionally help in biocontrol of the aphids in neighbouring fields, too. Normally no
chemical treatments are needed for alfalfa even at the period of outbreak in population of its key pest, Hypera postica (Gyllenhal). It has also been strongly
prohibited because of foraging value for the livestock. Occasional application of
chemical insecticide directly reflecting the emergence of large aphid populations
represented by Acyrthosiphon pisum (Harris).
The adult parasitoid leaves the treated patches and avoid oviposition in these
areas (Longley and Jepson 1996). The catastrophic aphid mortality following insecticide treatment can also result migration of the parasitoids to the nearby areas, where
they may fail to find suitable food resources. This phenomena is quite common in
isolated monocultures and cause a longer delay in establishing the new generation of
the parasitoids on the growing population of the survived aphids. Organic farming is
an alternative to the conventionally managed farms, in which a higher proportion of
semi-natural habitat are exist (Langer 2001). Inter-cropping as a model that enhances
the plants diversity (Gibson et al. 2007) and the pesticide application is prohibited
(Lampkin 1999) to improve colonization of aphid parasitoids. Within such environment, pest control process is naturally occurring by the same predators and parasitoids, but very efficiently in absence of the insecticides. Presence of alternate aphid
hosts, as well as food resources for the adult parasitoids enhance their efficiency in a
complex organic farming system (Langer 2001; Macfadyen et al. 2009).
9.6 Conservation of the Aphid Parasitoids
9.6.1 Concept of Refugiums for the Aphid Parasitoids
The term “refugia” has been originally used for a site or area where some rare/
endangered species have succeeded to survive. It has been used for the endemic
species, “living relics”, and potentially also for rare species which required conservation and environmental protection. In this respect, the meaning still has been
respectively used. However, diversification of the landscape and namely, the development of agroecosystems has determined some situations, where the pests as well
as useful natural enemies are concentrated and/or surviving after unfavourable
periods of the season, and may again re-expand in the environment. In the natural
plant community conservation programmes, it is easy to join it with the aphid and
parasitoids associations, as each aphid and a parasitoid is generally capable to find a
372
E. Rakhshani and P. Starý