Antifungal effect of Bonellia flammea extracts against Colletotrichum magnum in postharvest fruits of Carica papaya cv. Maradol

There is a high demand for natural agrochemicals to control postharvest phytopathogens in fruit. In this study, the Colletotrichum magnum strain was isolated from Maradol papaya fruits showing symptoms of anthracnose, identified based on its morphological characteristics and confirmed by an analysis of its 5.8S ribosomal DNA sequence. The antifungal activity of aqueous and ethanol extracts from Acacia pennatula, Acalypha gaumeri, Bonellia flammea, Calea urticifolia and Croton chichenensis was evaluated against Colletotrichum magnum by agar dilution bioassay at a concentration of 1 mg mL⁻¹ and recording mycelial growth inhibition (MGI), sporulation inhibition (SI) and spore germination inhibition (SGI) were recorded. The extracts that caused MGI of C. magnum by more than 30% were re-evaluated. It was concluded that the aqueous and ethanol extracts from B. flammea stem bark were the most effective in the MGI (91.53–94.49%), SI (99.32–99.65%), and SGI (91.65–100%) of C. magnum at a 3% (w/v) concentration. A serial dilution of the aqueous extract of B. flammea demonstrated that 2.35% and 3% (w/v) were highly effective against C. magnum in vitro, and both concentrations were randomly applied to postharvest Maradol papaya fruit by dip. The results found that both concentrations caused an anthracnose disease severity of 0.92–0.97% in papaya fruits, which was lower than the commercial fungicide Tecto 60®. The aqueous extract from B. flammea stem bark represents a promising opportunity for developing a natural biopesticide to effectively control anthracnose in papaya fruits induced by C. magnum.