Objective This study aimed to investigate the inhibitory effects of different Chinese herbal medicines on Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) and the biocontrol efficacy of herbal substrate, so as to screen efficient and safe botanical pesticides.

Method Six Chinese herbal medicines including Vetiveria zizaniodes were selected, and the inhibitory effects of their aqueous extracts against Foc TR4 were determined by the growth rate method. The ethanol extract of V. zizaniodes was further used to examine its inhibitory effect on spore germination and its impact on mycelial morphology of Foc TR4. Pot experiments were conducted to verify the biocontrol efficacy of V. zizaniodes substrate against Foc TR4 under natural conditions.

Result Significant differences in antifungal activity against Foc TR4 were observed among different herbal aqueous extracts. The aqueous extract of V. zizaniodes at a concentration of 50 g/L exhibited the strongest inhibition, with an inhibition rate of 36.73%, showing no significant difference from the positive control (white tea extract). The inhibitory effect of the ethanol extract of V. zizaniodes increased with concentration. At a final concentration of 2.000 mg/mL, the inhibition rate reached 45.80%, and the spore germination inhibition rate was 45.69%. Microscopic observation revealed that the mycelia of Foc TR4 treated with the ethanol extract of V. zizaniodes became uneven in thickness, with increased surface wrinkles and localized swelling, indicating a significant disruptive effect on mycelial structure. In pot experiments, the disease index of the treatment group inoculated with Foc TR4 and supplemented with V. zizaniodes substrate was 1.1, which was significantly lower than that of the control group inoculated with Foc TR4 alone (2.0, P < 0.05), indicating that the addition of V. zizaniodes substrate effectively suppressed the development of Fusarium wilt of banana.

Conclusion The extract of V. zizaniodes exhibits significant antifungal activity against Foc TR4 and possesses promising biocontrol potential, which can alleviate the damage caused by Fusarium wilt of banana. This study provides a theoretical basis and material foundation for the development of novel botanical pesticides.