Importance, etiology and management of the bacterial black spot disease of mango

Mango bacterial black spot is one of the most devastating diseases of mango worldwide, and it was recently identified in Ghana. Information on the prevalence and level of destruction caused by the disease in Ghana needs to be studied in detail. In this study, the disease prevalence, incidence and percentage of fruit destruction caused by the disease were determined in the major mango-growing areas of the country. Six species-specific primers were evaluated for their ability to identify Xanthomonas citri pv mangiferaeindicae, the causal agent of the disease. In addition, three copper-based fungicides, namely, Nordox (750 g/kg cuprous oxide), Coprous Super (850 g/kg copper oxychloride) and Funguran (770 g/kg copper hydroxide) either solely or in combination with Actigard (Acibenzolar-S-methyl) were evaluated for their effect on the disease severity in the field. The disease was found to be 100% prevalent in the major mango growing districts of Ghana, with incidence ranging from 26 to 94% in 2020 and 22–98% in 2021. The disease caused between 17 and 53% and 5.6–58% of fruit destruction at maturity in 2020 and 2021, respectively. The primer pair VM3/VM4 consistently amplified the expected PCR product of 150 bp from isolates of the causal agent. Combining copper-based fungicides with acibenzolar-S-methyl gave reasonable disease control by reducing the percentage of fruit abscission and blemished fruits at maturity. The findings have implications for managing the bacterial black spot disease in Ghana.