<![CDATA[Background: Acacia crassicarpa is widely cultivated in Industrial Forest Plantations but is susceptible to Fusarium wilt, which can cause severe seedling losses up to 36.94%. The limitations of synthetic fungicides highlight the need for sustainable biological control alternatives. This study evaluated biological agents and fungicides for suppressing Fusarium infection in A. crassicarpa seedlings. Methodology: The research was conducted at the Plant Protection Division (PPD) Research and Development Laboratory, Sinar Mas Forestry, Perawang, Riau. The experiment was arranged in a Completely Randomized Design (CRD) with seven treatments, three replications, and four seedlings per replication, resulting in a total of 84 seedlings. The treatment included negative control, a positive control, Fusarium endophyte, Trichoderma, DSE, Merivon, and Octave. Observation parameters consisted of disease symptoms, seedling mortality percentage, latent period, and control effectiveness. Data were analyzed using ANOVA at a 5% significance level, followed by Duncan’s Multiple Range Test (DMRT) for significant differences. Findings: The results indicated that the Fusarium endophyte and Octave fungicide treatment were the most effective, both achieving 100% control with no seedling mortality. Merivon fungicide showed 86% effectiveness with 8,33% mortality, while Trichoderma and DSE achieved moderate control with 57% and 43% effectiveness, respectively. The positive control exhibited the highest mortality rate at 58,33%. Re-isolation confirmed Fusarium as the primary causal pathogen responsible for seedling death. It can be concluded that both biological agents and fungicides effectively suppressed Fusarium infection on Acacia seedling. Contributions: The Fusarium endophyte shows great potential for development as an environmentally friendly biological control agents to support sustainable nursery management and reduce dependence on synthetic fungicides]]>
