Enhanced survival of mass-reared Mediterranean fruit flies via regular diurnal temperature oscillations

Authors: LEE, H - Orise Fellow; CARVALHO, L - US Department Of Agriculture (USDA); Manoukis, Nicholas

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2025
Publication Date: 2/10/2025
Citation: Lee, H., Carvalho, L.A., Manoukis, N. 2025. Enhanced survival of mass-reared Mediterranean fruit flies via regular diurnal temperature oscillations. Journal of Economic Entomology. 118(2):655-661. https://doi.org/10.1093/jee/toaf026.
DOI: https://doi.org/10.1093/jee/toaf026

Interpretive Summary: Producing insects in a factory setting is important for environmentally-friendly control techniques like Sterile Insect Technique (SIT) and for research. However, factory conditions, with constant temperature, humidity and light cycles, may not be conducive to producing the highest quality insects from the perspective of survival, reproduction, or other fitness-related traits. Here we investigated the performance of mass-reared adult Mediterranean fruit flies (Medflies) under constant (24 °C) and daily oscillating (24 ± 2 °C or 24 ± 5 °C) temperature regimes. We also tested whether an environmental chamber simulating outdoor conditions would lead to Medfly of similar quality as those reared outdoors. Male medflies under the oscillating temperatures had higher survival probability at 50 days post-emergence compared to the constant temperature regime, but females showed no significant differences in survivorship among temperature regimes. Flight ability and fecundity were not significantly affected by constant or oscillating temperatures. Environmental chamber and outdoor conditions led to similar performance metrics. Our findings suggest that the performance of mass reared male adult medflies can be increased by daily temperature oscillations by increasing male adult medfly longevity.

Technical Abstract: Effectively mass rearing insects is critical for research, application of environmentally friendly control technologies like Sterile Insect Technique (SIT), producing biological control agents, and enabling novel methods based on genetics or symbionts. While constant temperature conditions are typically used in mass rearing, based on the idea that there is an optimum value that produces the most fit insects, homeostatic conditions do not reflect the variable temperatures they encounter in the real world, potentially impacting their performance in the field. We investigated the performance of mass-reared adult Mediterranean fruit flies (Medflies) under constant (Const24: 24 °C) and oscillating (Osc2: 24 ± 2 °C, Osc5: 24 ± 5 °C) temperature regimes. Male and female survivorship, flight ability, and female fecundity were assessed across the temperature regimes. Additionally, we compared adult medfly performance under environmental chamber and semi-field conditions to determine if temperature and humidity as simulated in the chambers reflected conditions in nature. Male medflies under the Osc 5 treatment had higher survival probability at 50 days post-emergence compared to the constant temperature regime, while females showed no significant differences in survivorship among temperature regimes. Flight ability and fecundity were not significantly affected by temperature regimes, though the Osc 5 group showed the highest fecundity. Comparisons between environmental chamber and outdoor conditions revealed minimal differences in performance metrics. Our findings suggest that the performance of mass reared male adult medflies under temperature variance in the field can be improved by oscillating temperature regimes in mass-rearing protocols by increasing male adult medfly longevity. Our findings highlight the importance of considering environmental variability in both release and rearing strategies, potentially improving the efficacy of mass rearing programs.