Antifungal Effects of Silver Nanoparticles, Synthesized Using <i>Trichoderma harzianum</i> , on <i>Ganoderma boninense</i> Causing Basal Stem Rot on Oil Palm

Silver nanoparticles (AgNPs) exhibit strong antimicrobial properties against plant pathogens. However, studies on the application of AgNPs, synthesized using the fungus <i>Trichoderma harzianum</i>, to control the growth of <i>Ganoderma boninense</i> Pat, which causes basal stem rot (BSR) in oil palm (<i>Elaeis guineensis</i> Jacq.), have not been reported. Therefore, this study aimed to assess the potential of AgNPs, biologically synthesized using <i>T. harzianum</i>, as a biofungicide and evaluate their effect on the growth of <i>G. boninense</i> in vitro and in vivo. Secondary metabolite compounds were identified using Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS), and the presence of AgNPs was confirmed by a brown color change, followed by UV-Vis spectroscopy, particle size analysis, and in vitro testing. The FTIR and GC-MS results showed that isothiocyanate (N=C=S) and n-hexadecanoic acid (20.51%) were present as the antifungal compounds. The AgNPs synthesized using <i>T. harzianum</i> were detected at approximately 410 nm and had a nanoparticle size of 77.3 nm. In vitro application of the AgNPs at a concentration of 100 mg·liter^-1 exerted a significant inhibitory effect on the growth of <i>G. boninense</i>. This result was consistent with the findings on palm oil seedlings. The AgNPs-Th can suppress the severity of BSR disease and can stimulate the vegetative growth of oil palm plants. In conclusion, this study expanded the current understanding of antifungal effects of AgNPs synthesized using <i>T. harzianum</i> and revealed their potential to suppress BSR caused by <i>G. boninense</i> in oil palm plantations.