Fungal biocontrol agents in the management of soil-borne pathogens, insect pests, and nematodes: Mechanisms and implications for sustainable agriculture

This scoping review, conducted using the PRISMA-ScR framework, synthesizes evidence on the application of fungal biocontrol agents—Trichoderma, Beauveria, Metarhizium, and Paecilomyces—in managing soil-borne pathogens, insect pests, and plant-parasitic nematodes in agricultural systems. The review identifies and categorizes the primary mechanisms employed by these fungi, including microbial competition, direct parasitism, production of bioactive secondary metabolites, and stimulation of host plant defences. Across studies, Trichoderma species consistently suppressed soil-borne pathogens such as Fusarium and Rhizoctonia through competitive exclusion and metabolite production, with pathogen reductions reported up to 70 %. Entomopathogenic fungi like Beauveria bassiana and Metarhizium anisopliae caused insect mortality rates of up to 80 % by penetrating host cuticles and disrupting physiological processes. Paecilomyces lilacinus reduced nematode populations, particularly Meloidogyne spp., by 60–75 %, primarily through egg parasitism. Induced resistance was observed through enhanced activity of plant defense-related enzymes and signalling pathways following fungal inoculation. In addition to pest and disease suppression, several studies documented improvements in plant vigour and biomass, attributed to root colonization and enhanced nutrient availability. The evidence compiled highlights consistent trends in the multifunctional role of fungal biocontrol agents and their potential integration into sustainable pest management strategies. These findings support their consideration as environmentally compatible alternatives to synthetic agrochemicals in diverse crop production systems.