Pre-release dietary supplements of methoprene and raspberry ketone increase field abundance of sterile Queensland fruit flies (Diptera: Tephritidae).

The sterile insect technique (SIT) is a sustainable pest management tool based on the release of millions of sterile insects that suppress reproduction in targeted populations. Success of SIT depends on survival, maturation, dispersal, and mating of released sterile insects. Laboratory and field cage studies have demonstrated that dietary supplements of methoprene and raspberry ketone (RK) promote sexual maturation of adult Queensland fruit fly, Bactrocera tryoni (Froggatt), and may hence shorten the delay between release and maturity in the field. We investigated the effects of methoprene and RK dietary supplements on field abundance of sexually mature sterile Q-flies relative to untreated flies fed only sugar and yeast hydrolysate before release at 2 d of age. Compared with untreated flies, more methoprene- and RK-treated flies were recaptured in cuelure traps to which only sexually mature males are attracted. At distances of 100 and 200 m from the release point, recapture rates were higher for methoprene- and RK-treated flies than for untreated flies, but at 300 m recapture rates were low and were similar for treated and untreated flies. Rainfall, relative humidity, wind speed, and wind direction did not affect recapture rates, but temperature was positively correlated with recapture rates for all treatments. There was a strong correlation between the number of sterile and wild flies caught in traps, indicating co-location in the field. Dietary supplements of methoprene and RK can substantially increase abundance of sexually mature sterile male Q-flies in the field following release as 2-d-old immature adults.

Effect of Chilling on Quality Control Parameters of Sterile Queensland Fruit Fly (Diptera: Tephritidae).

Queensland fruit fly (Q-fly), Bactrocera tryoni (Froggatt), presents a major threat to Australian fruit production and trade. The sterile insect technique (SIT) is increasingly employed to manage Q-fly. Quality of sterile males released in SIT programs, and hence program efficacy, can be affected by pre- and post-production processes, such as mass rearing, packing, irradiation, transportation, and release. Given long distances from rear-out facilities to release sites, adult flies are usually chilled to reduce metabolism and stress during transportation. To guide SIT procedures, it is important to understand the impact of such practices on performance of sterile Q-fly. The present study assesses the effect of chilling temperature and exposure period on quality parameters of sterile Q-fly. We considered the effects of two temperature regimes (4 and 6°C) and six exposure periods (0, 1, 2, 4, 6, and 12 h) on chill-coma recovery time, flight ability, survival under nutritional stress, and longevity of both males and females. Flies chilled at 4°C took longer to recover than that those chilled at 6°C. Flight ability, survival under nutritional stress, and longevity all decreased as chilling period increased but did not differ between the two tested temperatures. We recommend that periods of chilling during transportation from rear-out facilities to release sites be minimized in order to retain quality of sterile Q-fly and that increased release rates be considered when longer chilling periods are required.

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. © 2019 Society of Chemical Industry.

Cool storage of Queensland fruit fly eggs for increased flexibility in rearing programs.

BACKGROUND: The Queensland fruit fly (Q-fly) is Australia's most economically damaging insect pest of fruit crops. The Sterile Insect Technique (SIT) used to suppress outbreaks relies on supply of high-quality flies and this can be assisted by the ability to manipulate production schedules. Cool storage at temperatures that are sufficient to slow development without causing significant somatic damage can provide a valuable means of manipulating production schedules. In this study, we investigate the effect of four storage temperatures (10, 13, 16 and 19 °C) and three exposure times (3, 6 or 9 days) on Q-fly eggs. RESULTS: Egg storage proved effective in prolonging the developmental time of Q-flies. Storage at 10 °C was unsuitable, resulting in a low hatching rate for all exposure times. Hatching rate was also significantly reduced when eggs were exposed to 13 °C for 6 or 9 days, followed by a significant reduction in the number of pupae recovered. Storage at 16 °C yielded promising results, prolonging the preimaginal development of Q-flies up to 6.5 days without significantly affecting egg hatching or subsequent development. CONCLUSION: Cool storage of eggs shows promise as a tool for prolonging the development of Q-flies to manipulate schedules in mass rearing programs. © 2018 Society of Chemical Industry.