Microclimate selection in a tree canopy by wild, and fertile and sterile mass-reared Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) (#828)
Effective sterile insect technique (SIT) programs are entirely dependent on the ability of released flies to (1) survive in the field and (2) find and mate with wild flies. However, the mass-rearing environment used to rear the millions of flies required each week for SIT may produce sterile flies that are not adequately capable of either key task. Surprisingly, to date, there have been no direct measurements of the ability of sterile Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) to adjust to field conditions despite their use in area-wide management of the species for over two decades. We assessed the diurnal behaviour, spatial distribution and microclimates favoured by wild, fertile mass-reared, and sterile mass-reared B. tryoni, and their survival, in potted citrus trees within field cages. Wild B. tryoni were more likely to feed on flowers and the upper leaf surface of leaves than either fertile or sterile mass-reared flies. Height of all B. tryoni types varied during the day. Mean height was highest at dusk, and lowest at midday when temperatures were high, humidity was low, and light intensity was high. Survival of fertile and sterile mass-reared flies was lower than that of wild B. tryoni. Our results indicate that B. tryoni, regardless of their origin, select microclimates in tree canopies during the day to avoid stressful conditions. We suggest that lower survival in fertile and sterile mass-reared flies is a consequence of selection for a short lifespan by the mass-rearing environment.