Plant Fungal Endophytes as Sustainable Components of Insect Pest Management

Agricultural systems are designed to meet the increasing global demand for food. However, pests pose a significant threat to agricultural productivity, potentially hindering the ability to meet the demand. Biological control is considered an effective method to manage these pests and tackle food loss. Among the various biological agents, endophytic fungi stand out as a promising alternative to insecticides due to their numerous beneficial effects. In this review, we summarize the reports on the major phyla and classes of endophytic fungi as well as their identified sources. Endophytic fungi are known to synthesize insecticidal metabolites that directly help to prevent pest invasion, reduce the pest's adaptability to their surroundings, and increase their sensitivity to natural enemies. Besides, several metabolites produced by the endophytic fungi signal the host plant to produce its defense chemicals, triggering the plant's immune response and thereby enhancing its resistance. Therefore, the review further discusses the direct (endophyte-insect interactions) and indirect effects of the endophytic fungi on the insect pests (enhanced plant defense) and provides evidence to support their significant role in the endophytic fungus-plant-insect triadic relationship. Taking these reports into consideration, we suggest that endophytic fungi could serve as a significant component of sustainable pest management. However, the negative impact of the fungal metabolites on the mammals that consume the host plants needs to be investigated.