Quantification and Impact of Cold Storage and Heat Exposure on Mass Rearing Program of Bactrocera dorsalis (Diptera:Tephritidae) Genetic Sexing Strain

SIMPLE SUMMARY: Storing insects at low temperature has been an effective approach for mass rearing programs, which can increase the shelf-life of bioagents and flexibly manipulate their pre-release periods. However, introducing insects to temperatures outside of their accustomed range can lead to stress and thereby influence their quality and competitiveness in the field. Bactrocera dorsalis is an economically important pest can devastate many fruits and vegetables, and cold storage has been used in storing, packing and shipping of sterile B. dorsalis males to control the wild population, but the impact of cold storage on the quality of B. dorsalis has never been investigated. Here, we examined the impacts of pupal cold storage on developmental parameters and quality of B. dorsalis adults. Overall, we found that pupal cold storage has a negative effect on some biological parameters of B. dorsalis, especially in fecundity. Thus, heat exposure was further conducted on the post-storage adults, and our results show that short-term heat exposure could partially compensate for the loss in fecundity in B. dorsalis adults resulting from the pupal cold storage. Our findings indicate that the flexibility of the B. dorsalis mass rearing program could be improved by utilizing cold storage and heat exposure. ABSTRACT: Cold storage and heat exposure are crucial components of tephritid fruit fly mass-rearing programs, as they influence the development and fitness traits of produced flies. This work investigated the effects of cold storage on the pupal developmental parameters and quality of Bactrocera dorsalis (Hendel) genetic sexing strain (GSS) adults. Furthermore, the impact of short-term thermal exposure on the fecundity of B. dorsalis (GSS) that also underwent pupal cold storage was examined. Our results show that pupal development time, emergence rate, partial emergence rate, flight ability and fecundity were significantly affected by low temperature and pupal age and their interaction. Pupal cold storage did not pose negative impacts on the mating competition and response to methyl eugenol (ME) in the males. In addition, compared with the adults that were subjected to the same pupal storage protocol (five-day-old pupae stored at 13 °C), adult exposure to 41 °C for 1 h showed significant reparative effects on fecundity. In summary, the cold storage procedure of B. dorsalis (GSS) pupae has the potential to improve the flexibility and efficiency of mass-rearing schedules. Furthermore, short-term thermal exposure showed reparative effects on the fecundity costs induced by pupal cold storage in B. dorsalis (GSS).