Sterile Queensland fruit flies Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) are commonly marked with fluorescent dye to assist with subsequent identification after release and recapture. The impact of dye on adult eclosion and flight ability was tested using eight concentrations of dye (Swada, Fiesta Astral Pink) from 0 to 4.5 g/L of pupae. There was no significant difference in eclosion rates between undyed pupae (control) and pupae dyed at a concentration of 1.0 g/L. For dye concentrations of 1.5-4.5 g/L, adult eclosion rates declined from 85.7% to 77.4% and were significantly different from the control. Flight ability indices ranged from 92.1% to 83.3%. There was no significant difference in flight ability between control pupae and those dyed at 1.0 g/L and 3.5 g/L pupae, but other pupae from other dye concentrations were significantly different from the control. Pupal weight ranged from 8.3 to 10.2 mg and there was no significant relationship between pupal weight and adult eclosion or flight ability.

From 1996 to 2012, the mass‐rearing facility at Camden (NSW, Australia) has been producing Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae). During this time, the facility has regularly recorded fly quality parameters, creating a unique data set that provides an invaluable opportunity to evaluate the interrelationships among standard quality control (QC) parameters and test for redundant QC variables. Here, we conducted an exploratory data analysis to reveal relationships among the QC parameters. We found that pupal weight, adult lifespan, and longevity under nutritional stress (i.e., survival duration without food or water) had distinct monthly trends, suggesting that these QC parameters are sensitive to seasonal conditions. Furthermore, emergence percentage, flight ability, and adult lifespan were adversely affected by the dyeing/handling/irradiation process associated with sterile insect releases. Using a multivariate approach and controlling for monthly and yearly patterns, we showed that pupal weight and egg hatch are consistently negatively related and that percentage male and emergence rates are consistently negatively related. These results suggest that these correlation pairs measure similar quality information and hence one QC variable from each pair could be dropped. Flight ability was not strongly correlated with any of the QC variables, suggesting that this QC variable remains a useful QC metric. Finally, the longevity under nutritional stress QC appears to be fairly insensitive to QCs and we suggest that it should be replaced by the standard mortality under stress test.

The sterile insect technique has been routinely used to eradicate fruit fly Bactrocera tryoni (Froggatt) incursions. This study considers whether fly quality in a mass-rearing facility can be improved by reducing irradiation doses, without sacrificing reproductive sterility. Pupae were exposed to one of five target irradiation dose ranges: 0, 40-45, 50-55, 60-65, and 70-75 Gy. Pupae were then assessed using routine quality control measures: flight ability, sex ratio, longevity under nutritional stress, emergence, and reproductive sterility. Irradiation did not have a significant effect on flight ability or sex ratio tests. Longevity under nutritional stress was significantly increased at 70-75 Gy, but no other doses differed from 0 Gy. Emergence was slightly reduced in the 50-55, 60-65, and 70-75 Gy treatments, but 40-45 Gy treatments did not differ from 0 Gy, though confounding temporal factors complicate interpretation. Reproductive sterility remained acceptable (> 99.5%) for all doses--40-45 Gy (99.78%), 50-55 Gy (100%), 60-65 Gy (100%), and 70-75 Gy (99.99%). We recommend that B. tryoni used in sterile insect technique releases be irradiated at a target dose of 50-55 Gy, providing improved quality and undiminished sterility in comparison with the current 70-75 Gy standard while also providing a substantial buffer against risk of under dosing.

The sterile insect technique has been used for more than 50 years to control a range of insects around the world. Sterile insect technique is rapidly becoming a major component of many area‐wide fruit fly management programmes. Irradiation of immature life stages induces sterility in adults, which are then distributed over large areas to mate with wild flies, resulting in no viable offspring. However, irradiation in normal air results in declining adult quality. To optimize the quality of sterile adult flies, several techniques are available to lower the levels of oxygen in fruit fly tissues prior to irradiation. The simplest method is to seal pupae in plastic bags and allow the oxygen consumption of pupae to minimize oxygen in both the air and pupal tissue. Some fruit fly species have rapid decreases in eclosion as a result of low oxygen atmospheres. We tested the tolerance of Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), to low oxygen for the first time. In the first two experiments, unirradiated B. tryoni pupae were tested for different periods in sealed plastic bags at 17, 21, and 26 °C. Optimum eclosion occurred at 21 °C with the lowest eclosion at 26 °C. In general, mean full eclosion declined at ca. 0.1% eclosion per hour sealed in plastic bags during the first 96 h for all temperatures. In the third and fourth experiments at 17 °C, there was a decline in average eclosion for irradiated and unirradiated pupae of about 13.4% after they were sealed in plastic bags for 192 h. In general, B. tryoni eclosion declined at 0.1% per hour inside sealed plastic bags for periods up to 192 h at 17 °C. Queensland fruit flies can tolerate long periods of conditions found inside sealed plastic bags and current practices for sterile B. tryoni release programmes will result in minimum decrease in eclosion. The possible evolution of tolerance of these conditions is discussed.

The sterile insect technique is used to manage or control fruit flies throughout the world. The technique relies on large scale production before delivery to release managers. As part of the mass production phase, there are many quality control tests to demonstrate and maintain high quality pupae and flies. One highly desirable characteristic is adults with a long life so that these adults can reach sexual maturity and sterile males mate with wild fertile flies in the field and thus produce no viable offspring. Originally longevity was assessed allowing adults to have unlimited access to food and water. As quality and longevity increased, this methodology added significantly to workload and space demands and many facilities moved to testing longevity under stress where no food or water was provided. Here we examined >27,000 Queensland fruit fly Bactrocera tryoni (Froggatt) from 160 weekly production batches from July 2004 to October 2009 where flies were not provided food or water. The mean longevity was 54.4 ± SE hours. Longevity was significantly shorter from August to March, and the longevity was significantly longer in June. Longevity was not related to pupal weight, contrary to expectations. Weights were significantly lower in June and highest in summer.