Bactrocera dorsalis invasion increased fruit fly incidence on mango production in Reunion Island. (November 2022) - Grechi, Isabelle
Abstract: Fruit flies (Diptera: Tephritidae) are considered to be major pests of mango ( Mangifera indica L.) worldwide. A new invasive fruit fly species, the oriental fruit fly, Bactrocera dorsalis (Hendel), has been recently identified in Reunion Island. Previous reports recorded very high production losses due to B. dorsalis and suggested that it may competitively eliminate other fly species. The main objective of this study was to assess the impact of B. dorsalis invasion on mango fruit production in Reunion Island and its implication on management recommendations. Studies under field conditions and choice tests in laboratory conditions were carried out in Reunion Island before (2015–2017) and after (2019–2020) B. dorsalis invasion in order to characterize how fruit fly incidence on mango production and fruit infestation response to fruit maturity has evolved since the invasion. B. dorsalis was by far the most frequently trapped fly species in 2019–2020. Whereas mango fruits were mainly infested by Bactrocera zonata (Saunders) in 2015–2017, they were exclusively infested by B. dorsalis in 2019–2020. The probability of fruit infestation has globally increased by a factor of 3.5 on 'Cogshall' fruits and 2.4 on 'José' fruits following B. dorsalis invasion. For both fly species and mango cultivars, the infestation probability of fruits increased as fruits ripened, whereas the number of juveniles per infested fruit tended to be higher for unripe fruits. The infestation probability of unripe fruits was low under field conditions both before and after B. dorsalis invasion (infestation probability ≤0.05 for 'Cogshall' and ≤0.07 for 'José'). Under laboratory conditions, however, unripe 'Cogshall' fruits could be highly infested by B. dorsalis (infestation probability >0.42). The field study suggests that fruit fly damage can still be reduced by adjusting harvest timing, even after B. dorsalis invasion. Nevertheless, the capacity of B. dorsalis to infest unripe fruits in laboratory conditions calls for vigilance when applying these management recommendations. Highlights: Fruit fly incidence on mango in Reunion has increased since B. dorsalis invasion. 'Cogshall' and 'José' fruits have become exclusively infested by B. dorsalis . Fruit infestation by both B. zonata and B. dorsalis increases with fruit maturity. Adjusting harvest timing remains relevant to manage fruit fly damage on mango.