Mango phenology and fruit fly population dynamics in the transition zone of Ghana.

Abstract

Crop phenological studies are vital in the formulation of effective integrated pest management packages. A 2-year phenological study spanning 2017-2019 was conducted in eight mango orchards in the transition zone of Ghana, to determine the relationship between the aggregation of culprit fruit fly species and the phenology of the mango crop. A total of 160 shoots were tagged and observed weekly for the plant's developmental processes using the Biologische Bundesantalt, Bundessortenamt and Chemische Industrie mango phenological scale as a guide. Fruit fly monitoring was conducted with two para pheromone attractants (methyl eugenol and terpinyl acetate) in 32 improvised traps. Host fruits sampled at colour break and ripe stages were incubated to identify culprit species. Significant infestation levels were assessed with one way analysis of variance. Three culprit species (Bactrocera dorsalis, Ceratitis cosyra and Ceratitis ditissima) emerged from incubated fruits. Co-infestation between B. dorsalis and C. cosyra was observed mostly at colour break. A residual population of B. dorsalis was observed throughout the crop cycle but peaked at the colour break phenological stage in May and early June, and dropped in August (at post-harvest). The interaction among fruit fly species, season, fruit source and phenological stage of the fruit was significant (P = 0.016). C. cosyra appeared at the beginning of anthesis, increased during flowering to fruit set and peaked in April when fruits were nearing maturity and green. It is therefore important that management practices are implemented throughout the phenological cycle of the crop but intensified from anthesis to post-harvest to reduce pest populations and damage.