The efficacy of Black Afara Leaves Extracts in Inhibiting the Growth of Ralstonia solanacearum Causing Rhizome Rot in Fingerroot.

Abstract

Fingerroot (Boesenbergia rotunda) is a widely cultivated medicinal plant and culinary spice in Thailand. Farmers in the region often suffer severe losses due to rhizome rot, primarily caused by Ralstonia solanacearum. Traditionally, chemical pesticides have been used to manage thisdisease, but their use results in toxic residues. As a result, alternative, eco-friendly approaches fordisease control have gained attention, including the use of plant extracts with antimicrobialproperties. This study evaluated the efficacy of crude extracts from black afara (Terminalia ivorensis A. Chev) leaves in inhibiting Ralstonia solanacearum, the pathogen responsible forrhizome rot in fingerroot. The antimicrobial activity was assessed using the paper disc diffusionmethod on Tetrazolium Chloride Agar (TZC), testing both fresh and dried black afara leaf extractsat concentrations of 20,000, 40,000, 60,000, 80,000, and 100,000 ppm, with sterilized distilledwater serving as a negative control. The results demonstrated that crude extracts from both freshand dried black afara leaves significantly suppressed the growth of Ralstonia solanacearum (P≤0.05), with higher concentrations leading to greater inhibition. These findings suggest that blackafara leaf extracts offer a promising alternative for managing plant diseases efficiently and reducingreliance on chemical pesticides.