Methyl eugenol and pre-release diet improve mating performance of young Bactrocera dorsalis and Bactrocera correcta males

The objective of this extensive series of experiments, involving more than 2800 field cage tests with potted mango trees, was to assess pre-release supplements to enhance the mating success of sterile male Bactrocera dorsalis and Bactrocera correcta. We examined the effects of different pre-release diets and methyl eugenol (ME), both independently and in combination. Tests were carried out more than 15 and 18 days for B. dorsalis and B. correcta, respectively, each day increasing the age of sterile flies. To evaluate the effect of different pre-release diets on males, no-choice mating tests were conducted with sterile males of increasing age and mature sterile females. Sterile males fed up to 2 days of age on sugar–yeast hydrolysate combinations achieved significantly more matings than males fed only water in B. dorsalis and more matings than males fed only sugar, only yeast hydrolysate or only water in B. correcta. To examine the effect of ME on mating performance, 2-, 3-, 4- or 5-day-old sterile males were given or not given access to ME for 1 h, followed by the sugar–protein diet until the day of the mating test. Mating performance tests were carried out with ME-exposed and non-exposed sterile males competing with mature wild males for wild females. Results showed a significant mating advantage of ME-exposed over non-exposed sterile males, although at younger ages they were still less competitive than wild males. The interaction of sugar–yeast hydrolysate diet and ME as pre-release treatments for 2- and 3-day-old sterile males was assessed in terms of male sexual competitiveness. Overall, the combination showed an additive effect on increased mating success in B. dorsalis sterile males when competing a wild males for wild females, while in B. correcta males the drastic improvement in mating success was mainly linked to the ME exposure.