Potential of some cultural levers for fruit fly management on mango in Réunion

In Reunion, fruit flies (FF) (Diptera: Tephritidae) are major mango pests. Harvest stage optimization and prophylactic elimination of early infestation sources were assessed from 2015-2020, on “Cogshall” mango cultivar, both before and after detection of the invasive oriental FF Bactrocera dorsalis in the island, in 2017. From 2015-2017, fruits were mainly infested by Bactrocera zonata (92%), followed by Ceratitis spp, with a mean infestation level of 7.3%. From 2018-2020, they were infested exclusively by B. dorsalis, with a mean infestation level of 20%. Results obtained in 2015- 2017 and 2018-2020 under both natural and artificial infestation with both Bactrocera spp suggest that harvesting mangoes at an early maturity stage (“green-mature” or very early “yellow-point”) is conducive to a low infestation level by FF, without fruit quality being adversely affected. Observations of small mango fruits during early fruit drop (i.e. about 2-4 weeks after fruit set) showed that green growing fruits on the tree were barely infested (0% in 2018, <2% in 2019), whereas those close to abscission and those fallen on the ground sustained heavy infestation rates (means of resp. 16% and 36%). These early dropped small fruits may therefore serve as sources of FF outbreaks in orchards. Infestation of these fruits was lower on a woven plastic cover than on bare soil or resident vegetation-covered soil. Parasitism by micro-wasps was anecdotal at that stage. The compatibility of these new control levers with those earlier identified for the same or other mango pests (e.g. the mango blossom gall midge) is discussed.