Ganoderma boninense-induced basal stem rot (BSR) remains among the most significant challenges to oil palm productivity and sustainability in Malaysia. Accompanying this, "Sawit Shield", a bio-inoculant based on Trichoderma, developed from endophytic strains isolated from naturally recovered palms, was evaluated by widespread nursery and multi-year field trials. At the nursery stage, premature inoculation with "Sawit Shield" successfully suppressed Ganoderma infection, in which treated seedlings had only 23.3%–30.0% disease incidence but infected non-treated controls had 100%. Field testing was conducted at Pegagau Estate (Semporna) and Pitas Estate (Kudat), both of which are high-risk locations and have been worst-hit by Ganoderma attacks. The Sawit Shield-treated palms in Pegagau were only 0% infected at 60 months, as opposed to the controls at 4.17%. Similarly, 36 months observation at Pitas reported 0% infection from the treated plots against 11.67% in controls. Treated palms in Pegagau outperformed controls in fresh fruit bunch production throughout four years with a maximum of 32.94 Mt/ha and with significantly higher average bunch weight each year. These findings justify "Sawit Shield"'s consistent ability to suppress disease development and optimize agronomic performance under on-farm field conditions. Aside from disease control, environmental benefits were also achieved, for instance, reduced reliance on chemical fungicides and fertilizers (by 15–20%) and valorization of palm oil mill by-products in formulation. With proven efficacy, environmental value, and industrial adaptability, "Sawit Shield" is an expandable, environment, social and governance (ESG)-suited biocontrol solution for sustainable oil palm plantation management.