Entomopathogenic fungi as dual-function biocontrol agents: persistence and microbiome modulation in date palm soils

Entomopathogenic fungi (EPF) are sustainable biocontrol agents, yet their effects on native soil microbiota are not well understood. Here, we studied the persistence of Metarhizium brunneum and Beauveria bassiana as preventive treatments for date palms against the red palm weevil, Rhynchophorus ferrugineus, along with microbial community monitoring. Using fungal isolation and high-throughput metagenomics, EPF persistence assays, and continuous monitoring of date palm health, the changes in microbiota following application were assessed. First, it was evident that EPF preemptive treatments benefit palm protection against the weevil. While both EPF persisted for 180 days post-application, their effectiveness diverged, with B. bassiana having a longer protection period. Overall community composition showed no major changes following EPF applications; however, transient alterations favored local EPF genera, with dominant taxa being more likely to persist. EPF from less diverse families caused more substantial shifts, enhancing nitrogen-fixating bacteria, carbon-degrading bacteria and ammonia-oxidizing archaea, thereby affecting nutrient cycling. Beauveria bassiana induced the strongest temporal effects on diversity, while Metarhizium brunneum was more persistent but showed no significant changes in Shannon or Simpson indices compared to control. These results highlight EPF as multifunctional agent shaping soil microbiomes, with implications for biocontrol success and ecosystem function.