Pupal release of the Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), in the sterile insect technique: seasonal variation in eclosion and flight

Abstract

The Queensland fruit fly, Bactrocera tryoni (Froggatt), is the most significant pest of edible fruit in Australia. For the control of B. tryoni using sterile insect technique (SIT), either pupae or adults may be released. Using pupal release, this study tested the seasonal effect of different pupal loadings on eclosion and the flight of sterile B. tryoni. Pupal eclosion boxes were loaded with either 200, 350, 500, 650 or 800 g of pupae during five periods of the fruit fly season (August, October, December, February and April). Adult flies were allowed to emerge and the remaining pupal debris was sampled to determine the per cent emergence and per cent fliers. The duration of emergence, dye retention on the ptilinum of the flies, and temperature and relative humidity externally and internally of the eclosion boxes were recorded. The percentage of emergence was influenced by both pupal loading and the period of release. Overall, the percentage of emergence was lower for loadings of 200 and 350 g of pupae in August, October and April as compared with the 500 g or higher loadings. This difference was not apparent in December or February. The mean percentage of emergence for each pupal loading in December, February and April was well above 65%, the minimum required emergence parameter for successful sterile B. tryoni release. Across all pupal loadings, the percentage of fliers was greater than 99.3% in December, 87.8% in February and 80.8% in April. A high percentage of fliers (>92.7%) was recorded in October, but the percentage of emergence in August and October was below 65% for all pupal loadings; thus pupal release is a suboptimal SIT method during this period of time. Dye on the ptilinum was detected on every fruit fly sampled across all pupal loadings and release periods. Minimum temperature for optimal pupal emergence should not fall below 10°C, and the maximum should not exceed 35°C. Minimum temperature for successful flight should not fall below approximately 6°C while the maximum temperature should exceed 16°C. The described pupal release system is considered a possible option for use as part of an SIT program against B. tryoni under suitable environmental conditions in Australia.

MarkingBactrocera dorsalis(Diptera: Tephritidae) with Fluorescent Pigments: Effects of Pigment Colour and Concentration

“…Blaze 5, with a characteristic orange colour, also exhibited good visibility for up to 28 days after adult eclosion. Astral Pink 1 in the FEX series produced by Swada (rather than the T-series used here) has been used as a standard colour to mark sterile flies with a concentration of 0.8 g/100 g pupae in SIT programmes against B. tryoni (Reynolds et al 2010). Similarly, Blaze 5 matches the DayGlo ® colour recommended for use in SIT by the International Atomic Energy Agency (FAO/IAEA/USDA 2014).…”

“…The technical data sheets for the tested T-series pigments (Safety Datasheets, T-series, Swada, Cheshire, U.K.), as well as the FEX-series used in other studies (Reynolds et al 2010), state that they have limited lightfastness in exterior applications. The visibility of pigment marks has been shown to differ when viewed under light of different wavelengths.…”

“…Moistened vermiculite was used to enhance adult eclosion. The vermiculite was moistened prior to use by immersing in hot water at a ratio of 4:1 and cooled overnight (Reynolds et al 2010). Insect cages (24 in total) with dimensions 32.5 × 32.5 × 32.5 cm (BugDorm-43030, MegaView Science, Taichung, Taiwan) were placed along a laboratory bench next to five adjacent windows so that flies experienced a natural light cycle of approximately 12L:12D h. Allocation of treatments to cages was random.…”

“…Volumetric concentrations of 2 g/l pupae for the olive fly, Bactrocera oleae (Gmelin) (Rempoulakis & Nestel 2012), and 5 g/l pupae (Peck et al 2005) or 3 g/l pupae (Shelly & Edu 2010) for the melon fly, Zeugodacus cucurbitae (Coquillett), have been used. Concentrations of pigments by weight of pupae such as 0.8 g/100 g pupae (Reynolds et al 2010) and 0.5 g/100 g pupae (Meats & Edgerton 2008) have also been used for marking B. tryoni. Comparison of results from different fluorescent pigment marking trials is challenging as the weight and volumes of different cohorts of pupae differ substantially according to strain or rearing system (FAO/IAEA/USDA 2014).…”

Evaluating Irradiation Dose for Sterility Induction and Quality Control of Mass-Produced Fruit Fly <I>Bactrocera tryoni</I> (Diptera: Tephritidae)

“…SIT has been used more frequently for research or management since the early 1990s (Horwood and Keenan 1994, Meats et al 2003, Worsley et al 2008, Reynolds et al 2010, Reynolds and Orchard 2011. The current B. tryoni irradiation procedures for SIT, recommending a target dose of 70 Ð75 Gy , are based on the Þndings of Monro and Osborn (1967), Bhatti and Shipp (1972), Hooper (1978), and Sproul et al (1992).…”