Abstract
The use of irradiated hosts in mass rearing tephritid parasitoids represents an important technical advance in fruit fly augmentative biological control. Irradiation assures that fly emergence is avoided in non-parasitized hosts, while at the same time it has no appreciable effect on parasitoid quality, i.e., fecundity, longevity and flight capability. Parasitoids of fruit fly eggs, larvae and pupae have all been shown to successfully develop in irradiated hosts, allowing a broad range of species to be shipped and released without post-rearing delays waiting for fly emergence and costly procedures to separate flies and wasps. This facilitates the early, more effective and less damaging shipment of natural enemies within hosts and across quarantined borders. In addition, the survival and dispersal of released parasitoids can be monitored by placing irradiated sentinel-hosts in the field. The optimal radiation dosages for host-sterility and parasitoid-fitness differ among species, and considerable progress has been made in integrating radiation into a variety of rearing procedures.
Highlights
Augmentative parasitoid/predator releases are an environmentally-friendly means of pest population suppression that are useful when the pest has a greater rate of increase than its natural enemies and/or its populations begin to increase at times and places where natural enemies are not initially abundant [1,2]
Further studies on C. capitata and A. fraterculus exposure to X-rays [45,46] find that larval volume/density within the irradiation device affects even more than gamma radiation dosage formulations [19,44,47]
One comparison of D. longicaudata reared on irradiated and non-irradiated hosts found no significant differences in the mentioned parameters except for a lower rate of pupation in those larvae that had failed to mature within 72 h of irradiation [19]
Summary
Augmentative parasitoid/predator releases are an environmentally-friendly means of pest population suppression that are useful when the pest has a greater rate of increase than its natural enemies and/or its populations begin to increase at times and places where natural enemies are not initially abundant [1,2]. Naturally occurring parasitoid population densities cannot suppress pest populations to the minuscule levels required for commercial fruit and vegetable production and export [3] These issues can be addressed to one degree or another thURXJK DXJPHQWDWLYH UHOHDVHV )RU H[DPSOH 3UHIXJLD FDQ EH breached by releases of larval parasitoids into patches of smaller fruit whose shallow pulp cannot shelter hosts or by the use of species that attack shallowly-buried eggs that are vulnerable in even the largest fruits. Regardless of efficacy, what makes natural enemy augmentation economically viable is a cost effective means of mass rearing [14] In this regard, fruit fly parasitoids have presented a number of challenges, some of which are being overcome through the use of nuclear technology. Sites storage and packaging for release is simplified and irradiated sentinel-host eggs and larvae can be used to monitor parasitoid survival and dispersal [14,25,27±29]
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