This study investigates the interaction between root-associated entomopathogenic fungi (R-AEF) and host plants, specifically focusing on how R-AEF manipulate host plants to attract herbivorous insects. The research evaluates the behavioral responses of cabbage root flies to host plants inoculated with R-AEF, *Metarhizium brunneum*. Key findings include: 1. **Leaf Reflectance and Phytohormonal Composition**: R-AEF inoculation caused a decrease in leaf reflectance in the near-infrared spectrum and an increase in the production of jasmonic acid, (+)-7-iso-jasmonoyl-L-isoleucine, and salicylic acid in certain parts of the host plant. 2. **Behavioral Responses**: Cabbage root fly females showed a significant increase in landing and oviposition on R-AEF-inoculated host plants compared to non-inoculated plants. This was observed both in wind tunnel experiments and field conditions. 3. **Propensity of Oviposition**: Field and greenhouse experiments demonstrated that cabbage root fly larvae and pupae were more prevalent on R-AEF-inoculated host plants, confirming the entomopathogenic capability of *M. brunneum*. 4. **Discussion**: The study provides evidence that R-AEF manipulate host plants to attract herbivorous insects, potentially increasing the dispersal of the fungus. This manipulation could have both positive and negative impacts on the host plants and insects, but overall benefits for the fungi. 5. **Conclusions**: The findings contribute to the understanding of complex tri-trophic interactions and manipulative strategies involving micro-organisms, host plants, and insect herbivores. The research was conducted using a combination of laboratory and field experiments, providing a comprehensive assessment of how R-AEF alter host plant traits and influence insect behavior.This study investigates the interaction between root-associated entomopathogenic fungi (R-AEF) and host plants, specifically focusing on how R-AEF manipulate host plants to attract herbivorous insects. The research evaluates the behavioral responses of cabbage root flies to host plants inoculated with R-AEF, *Metarhizium brunneum*. Key findings include: 1. **Leaf Reflectance and Phytohormonal Composition**: R-AEF inoculation caused a decrease in leaf reflectance in the near-infrared spectrum and an increase in the production of jasmonic acid, (+)-7-iso-jasmonoyl-L-isoleucine, and salicylic acid in certain parts of the host plant. 2. **Behavioral Responses**: Cabbage root fly females showed a significant increase in landing and oviposition on R-AEF-inoculated host plants compared to non-inoculated plants. This was observed both in wind tunnel experiments and field conditions. 3. **Propensity of Oviposition**: Field and greenhouse experiments demonstrated that cabbage root fly larvae and pupae were more prevalent on R-AEF-inoculated host plants, confirming the entomopathogenic capability of *M. brunneum*. 4. **Discussion**: The study provides evidence that R-AEF manipulate host plants to attract herbivorous insects, potentially increasing the dispersal of the fungus. This manipulation could have both positive and negative impacts on the host plants and insects, but overall benefits for the fungi. 5. **Conclusions**: The findings contribute to the understanding of complex tri-trophic interactions and manipulative strategies involving micro-organisms, host plants, and insect herbivores. The research was conducted using a combination of laboratory and field experiments, providing a comprehensive assessment of how R-AEF alter host plant traits and influence insect behavior.