Effect of short-term suboptimal temperature storage to assist large-scale production of two dipterans: Exorista larvarum (L.) and Bactrocera tryoni (Froggatt)

Efficient rearing techniques providing high-quality insects are essential for pest control strategies entailing mass rearing and release in field, such as augmentative biological control and Sterile Insect Technique (SIT). Storage at suboptimal temperatures is a valuable procedure for prolonging the developmental time of insects and thus increasing the efficiency of insect rearing. The advantages that this procedure offers include a more flexible rearing schedule, the possibility to overcome periods of low production and the synchronization of field releases during pest outbreaks. Methods for storage of two model fly species, Exorista larvarum (L.) (Diptera: Tachinidae) and Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), were studied in the present thesis by investigating the best conditions for an efficient storage and the consequences for fly quality. Native to the Palearctic region, E. larvarum is a parasitoid introduced, and now established, in the USA as a biological control agent of Lymantria dispar (L.). The possibility to store the tachinid eggs at suboptimal temperatures once placed on artificial medium was first evaluated. Results showed that storage of the tachinid fly is possible to create a useful reserve of immatures, but the quality of the resulting females can be compromised. In addition, a study was performed with the aim of creating a useful stockpile of E. larvarum 1-day old puparia for use in small- or large-scale rearing programs. Pupal stage was efficiently prolonged by the storage treatments but female flies displayed a fitness reduction in some cases. Bactrocera tryoni (Queensland fruit fly, Q-fly) is an endemic phytophagous species that represents a serious biosecurity challenge for Australia, attacking many commercial fruit and vegetable crops. The possibility to create a useful reserve of Q-fly eggs by placing them on a gel-based diet and by storing them at different suboptimal temperatures was investigated. The preimaginal development was efficiently prolonged, but detrimental effects on biological parameters were observed. The following study evaluated the effects of suboptimal temperature storage on 1-day old Q-fly pupae for use in SIT programs. Survival and quality of the resulting adults were assessed and negative effects, of various intensity, were shown on standard and non-standard quality control parameters.