Endophytic entomopathogenic fungi: The next frontier in mycological biocontrol.

Entomopathogenic fungi (EPF) are eco-friendly alternatives to chemical pesticides. However, high costs, the instability of the formulations, sensitivity to environmental factors and variability in virulence limit adoption by farmers. We argue that these problems can be overcome by using EPF strains established as endophytes. The ability of endophytic entomopathogenic fungi (EEPF) to modulate the release of volatiles to attract the predators of insect pests positions them as dual-purpose biocontrol agents in agriculture. As endophytes, these fungi are persistent, lowering the costs for pest control. Endophytic entomopathogenic fungi can also promote plant growth and improve tolerance to abiotic stress. Research on the molecular mechanisms underlying plant tissue colonization by EEPF, their persistence in plants and virulence towards insects suggests that EEPF acquire virulence factors and metabolic versatility through horizontal gene transfer from plants. Therefore, establishing and maintaining EPF as endophytes within plants may compensate for the loss of virulence associated with repeated in vitro subculturing of EPF on artificial media. However, despite these potential advantages of EEPF, challenges still remain, such as variability in endophytic colonization under field conditions, host specificity, ecological risks, and scalability. This review critically evaluates these limitations, focusing on well-studied genera, such as Metarhizium, Beauveria, and Lecanicillium, and outlines future directions for improving the reliability of the application of EEPF. By integrating ecological, molecular, and applied perspectives, we provide a comprehensive and updated framework that positions EEPF as next-generation biocontrol agents in sustainable agriculture.