Global increase in demand for palm oil has caused an intensification in oil palm plantation; however, production is greatly hindered by Basal Stem Rot (BSR) disease caused by Ganoderma boninense. There are many approaches to controlling BSR, although, there is no accurate, sustainable and effective method to suppress G. boninense completely. Hence, four phenolic compounds [Gallic acid (GA), Thymol (THY), Propolis (PRO) and Carvacrol (CARV)] were selected to evaluate their antifungal effect, ability to alter the mycelium morphology, and fungal cell integrity against G. boninense. Significant differences (p < 0.05) were observed and 94% of inhibition was exerted by GA on G. boninense growth. Scanning Electron Microscopy and High-Resolution Transmission Electron Microscopy observations revealed that GA and THY treatment caused severe damage to the mycelium and recorded the highest amount of sugar and electrolyte leakage. The study of cell integrity and morphological disruption has elucidated the reduction of G. boninense cell viability. Generally, our findings confirm the fungistatic effects of GA and THY. The evolution of phenolic compounds during the phytopathology studies indicated their coherence in eradicating the G. boninense. It is proposed that GA and THY had the potential to be developed further as a natural antifungal treatment to suppress G. boninense.

Basal stem rot (BSR) caused by a wood degrading fungus, Ganoderma boninense, is the major constraint in palm oil production. It degrades the wood components and causes palms to collapse, leading to heavy losses. Inefficacy in controlling this disease could be caused by the lack of understanding in how the pathogen establishes itself on the host concerning wood decay stages. This study aimed to understand and determine the role of benzoic acid on the suppression of G. boninense and production of ligninolytic enzymes responsible for wood decay. Further, the alteration in wood component structure due to G. boninense infection and its prevention were studied. Benzoic acid treatment resulted in more than 80% of inhibition in G. boninense growth. SEM and HR-TEM analysis confirmed the antifungal activity of benzoic acid by disruption of mycelial morphology and cellular ultrastructure. Moreover, the membrane permeability assay recorded enhanced cell mortality in benzoic acid treated mycelium. The degradation of oil palm woodblock caused 58.86 % wood dry weight loss at day 120. In contrast, reduction in dry weight loss (58.82%) was recorded in woodblock treated with concentrations of benzoic acid of 5 mM and above. It is concluded that the use of benzoic acid could inhibit or delay pathogen establishment in oil palm wood, leading to the sustainable management of BSR disease. Further, glasshouse and field trials are required to prove the consistency in current findings which may contribute to reduced land expansion to create new disease-free land for oil palm planting.