Effects of some cultural practices on mango inflorescence and fruit pest infestation and damage in Reunion Island: recent progress, on-going studies and future steps

Abstract

In Reunion Island, mango bug (Orthops palus), blossom gall midge (Procontarinia mangiferae) and each fruit fly (Bactrocera zonata) are major pests of mango. On the other hand, mango fruit producers are challenged to produce “more”, notably via the reduction of losses due to pests and diseases, and “better”, via fruit quality improvement and reduction of the adverse environmental impact of pesticide applications. Studies are undertaken, aiming at improving orchard management via the assessment of crop protection methods alternative to synthetic pesticides. Those encompass cultural practices such as pruning, soil mulching and harvest time, against mango bug, blossom gall midge, and fruit flies, respectively. Potential effects, desirable or not, of the implementation of these technical levers on tree functioning and fruit production are also evaluated, including their compatibility with other levers (e.g., irrigation). Thus, in view of optimizing harvest time, as a trade-off between fruit organoleptic quality and fruit fly infestation risk, the relationship between fruit maturity and fruit fly infestation was characterized in the laboratory on mango 'Cogshall' under artificial infestation with B. zonata. Preliminary results confirm that egg-laying preference increases as fruits ripen. The effect of soil mulching as a physical barrier to blossom gall midge pupation/emergence and further mango re-infestation, as well as its indirect effects on diapausing pupae and on the mango tree physiology via the soil microclimate, are also investigated. In addition, empirical relationships between microclimate in the vicinity of inflorescences on the one hand, and both mango bug damage and powdery mildew (Oidium mangiferae) infection rate on the other hand, will be examined on inflorescences exposed to the sun or located in the shade, in view of assessing the potential effect of pruning on the impacts of the pest and pathogen and their interactions on mango inflorescences.