Efficacy of phenolic extracts from Chromolaena odorata and Azadirachta indica in biocontrol of bacterial wilt in tomatoes

Bacterial wilt, caused by Ralstonia solanacearum, is a highly destructive disease that can reduce tomato yields by 80–90%. Chromolaena odorata and Azadirachta indica extracts are rich in phenolic compounds at contents of 339.16 and 261.95 mg GAE/g, respectively, and notably contain prominent levels of chlorogenic acid (5.64–14.44 mg/g) and rutin (15.16–20.45 mg/g). These extracts effectively inhibited R. solanacearum, each with a MIC of 10 mg/mL. The extract combination exhibited an additive antibacterial effect, with a combined FIC index of 1.5. Greenhouse experiments using a combination of A. indica and C. odorata extracts after bacterial inoculation achieved the highest control efficacy of 66.4%, giving an effectiveness comparable to the Physan bactericide. Moreover, tomatoes treated with the phenolic-rich extracts exhibited improved growth, highlighting their potential as a natural and effective alternative to conventional chemical agents.