Abstract: Recent laboratory studies of mass-reared flies in small cages have found that periods of just 24- or 48-h
access to yeast hydrolysate can substantially enhance mating performance of mass-reared male
Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) (‘Q-flies’). Using field cage
tests that provide a better approximation of nature, we here investigated whether access to yeast
hydrolysate for 48 h after adult emergence improves the ability of male and female mass-reared, sterile
Q-flies to compete sexually with wild-type flies that had been provided continuous access to yeast
hydrolysate. Mating probability of sterile males was significantly increased by 48-h access to yeast
hydrolysate; sterile males provided 48-h access to yeast hydrolysate had mating probability similar to
that of wild males provided continuous access to yeast hydrolysate, whereas sterile males deprived of
access to yeast hydrolysate had much lower mating probability. Unlike males, access to yeast hydrolysate
for 48 h did not increase mating probability of sterile female Q-flies. We instead found that wild
females provided continuous access to yeast hydrolysate had higher mating probability than sterile
females that did or did not have 48-h access to yeast hydrolysate. This result raises the possibility that
a bisexual Q-fly strain might operate essentially as a male-only release when the flies are given access
to yeast hydrolysate during a 48-h pre-release holding period. Sterile males given access to yeast
hydrolysate for 48 h mated significantly earlier in the evening than wild males and, as in other recent
studies, this tendency was associated with an increased tendency to mate on the trees rather than the
cage walls. There was no evidence of sexual isolation in this study, as wild and sterile mass-reared flies
showed no evidence of preferential mating with their own kind. Further studies are now needed to
assess the potential for pre-release access to yeast hydrolysate to improve sexual performance and
longevity of sterile, mass-reared, Q-flies in the field.
