Incidence, Severity, and Species Distribution of Fruit Flies in Relation to Agroecological and Environmental Factors in Sierra Leone

Abstract

Fruit flies (Diptera: Tephritidae) are major constraints to tropical fruit production, threatening food security and export markets. However, empirical data on their diversity and infestation dynamics in Sierra Leone’s mango systems remain limited. This study assessed fruit fly incidence, severity, and species composition across agroecological zones to inform integrated pest management (IPM) and phytosanitary strategies. Field surveys were conducted from June to December in eight mango orchards across Moyamba, Tonkolili, and Koinadugu districts. Populations were monitored weekly using McPhail traps baited with methyl eugenol, cue lure, trimedlure, and terpinyl acetate. Specimens were identified morphologically, while infestation severity was quantified as flies-per-trap-per-day (FTD). Diversity indices (Shannon-Wiener, Simpson, and Pielou’s evenness) and statistical models (ANOVA, GLMM) were applied to evaluate spatial, temporal, and phenological effects.The results revealed that atotal of 5,947 flies were recorded, dominated by Bactrocera dorsalis (74.5%), followed by Zeugodacus cucurbitae (15.1%), with Ceratitis spp. occurring at lower frequencies. Tonkolili exhibited the highest abundance and diversity (H′ = 1.45), whereas Moyamba showed reduced diversity (H′ = 0.40). Methyl eugenol was the most effective attractant (χ² = 89.34, p < 0.001). Fruit fly populations varied significantly with season and crop phenology, peaking during the vegetative stage and in October (incidence 12.4%; severity index 9.23 ± 0.89), before declining toward December. The findings identify B. dorsalis as the dominant pest, with infestation patterns shaped by agroecological conditions, lure efficacy, and phenology. Targeted deployment of methyl eugenol traps, coupled with seasonal surveillance and strengthened phytosanitary practices, is recommended to enhance sustainable fruit fly management in Sierra Leone.