Cool storage of Queensland fruit fly pupae for improved management of mass production schedules

BACKGROUND: Cool storage is a valuable means of manipulating insect development time. The Queensland fruit fly (Q-fly) is Australia's most economically significant pest of fruit crops. The present study investigates cool storage of Q-fly pupae for increasing production flexibility for sterile insect technique programs. Development time, survival and fly quality were assessed following continuous storage of 1-day-old pupae at temperatures ranging from 13 to 25 °C. 

RESULTS: Survival was reduced almost to zero by pupal storage at 13 and 15 °C, was greatly reduced by storage at 17 °C, and was modestly reduced by storage at 19 °C. Pupal development time was extended by 16 days at 17 °C and by 9 days at 19 °C. Cool storage negatively affected flight ability and depleted lipid reserves. Cool storage at 19 °C enhanced the ability of 3-day-old adults to recover from chill-coma compared to control flies, indicating cold acclimation. 

CONCLUSION: There is potential for use of cool storage in Q-fly mass rearing, especially to improve alignment between production and field releases. For the purpose of delaying the development time of Q-fly pupae with minimal quality reduction, storage at 23 °C is recommended for 1-day-old pupae.