Effect of the timing of pupal irradiation on the quality and sterility of oriental fruit flies (Diptera: Tephritidae) for use in sterile insect technique

Authors: FEZZA, T - Animal And Plant Health Inspection Service (APHIS); Follett, Peter; SHELLY, T - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Applied Entomology and Zoology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2021
Publication Date: 7/5/2021
Citation: Fezza, T.J., Follett, P.A., Shelly, T.E. 2021. Effect of the timing of pupal irradiation on the quality and sterility of oriental fruit flies (Diptera: Tephritidae) for use in sterile insect technique. Applied Entomology and Zoology. 56:443–450. https://doi.org/10.1007/s13355-021-00751-9.
DOI: https://doi.org/10.1007/s13355-021-00751-9

Interpretive Summary: The sterile insect technique (SIT) involves mass releases of sterile male fruit flies that mate with wild females and produce no offspring. SIT has been used to suppress or eradicate many important pest species including screwworm, tsetse fly, Mediterranean fruit fly, and codling moth. Oriental fruit fly has also been a target of SIT on Pacific islands. Questions remain about the best time to apply irradiation to maximize fitness in sterile males. In this study, male pupae were irradiated at 100 Gy at 1, 2, 3, and 4 days before emergence as adults. Two and 3 days pre-emergence was the best with 1 day resulting in a few fertile flies and 4 days impacting fitness. Results are useful for SIT programs against Oriental fruit fly.

Technical Abstract: The Sterile Insect Technique (SIT) is a target-specific, biologically based method used to control invading or established populations of pestiferous tephritids. SIT entails the release of large numbers of mass-reared, sterilized males of the target species to achieve sterile male x wild female matings, which yield infertile eggs and suppress the growth rate of the pest population. As documented for several tephritid species, sterilizing irradiation may have adverse effects on various biological parameters, including, life span, flight ability, and mating competitiveness. To minimize these impacts and ensure sterility, released flies must be irradiated at a precise dose at a specific and uniform age. The objective of the present study was to determine the impact of pupal age at the time of irradiation on flight ability, male survival, fertility, and mating competitiveness for the oriental fruit fly, Bactrocera dorsalis (Hendel). We concluded that flies irradiated as pupae 4 days before emergence were significantly compromised with respect to adult emergence, flight ability, male survival, and mating competitiveness when compared to flies irradiated 1, 2, or 3 days before emergence. Additionally, we determined that crosses between males irradiated 1 day before emergence with non-irradiated females yielded significantly more pupae than the same cross with males irradiated at 2, 3, and 4 days before emergence. These findings suggest that SIT programs can potentially irradiate pupae at 2 or 3 days before emergence without compromising the quality of the released flies, which would permit the distribution of flies over greater distances.