Aim for the roots! Plants modulate the multitrophic interactions between entomopathogenic nematodes, fungi, and plants in the soil matrix

Within the soil matrix, entomopathogenic nematodes (EPNs), Metarhizium and Trichoderma fungi share similar soil niches and/or overlap in their host range. These biocontrol agents represent valuable resources for biological control strategies, offering potential alternatives to synthetic chemical pesticides in integrated pest management programs. Their co-occurrence, however, can substantially influence their respective population dynamics. We hypothesized that entomopathogenic nematode chemotaxis would be impacted by the presence of fungal biocontrol agents due to factors such as competition for resources and the production of repellent compounds. Two-choice experiments assessed nematode attraction to insect hosts in the presence of fungal mycelia or fungal-infected hosts, and the influence of bean plants on these interactions. Results revealed that Heterorhabditis bacteriophora, Steinernema glaseri, and S. feltiae were generally repelled by M. brunneum, T. afroharzianum and T. guizhouense fungal presence, exhibiting a preference for healthy insect larvae. However, the presence of bean plants significantly mitigated this repellency, creating an area more attractive to EPNs. H. bacteriophora and S. feltiae exhibited attraction towards areas with both plants and fungal mycelia. Steinernema glaseri presented a species-specific response, repelled by M. brunneum but attracted to T. afroharzianum in the presence of plants. This research highlights the complex interplay between EPNs, fungi, and plants, demonstrating that plant-derived cues can modulate nematode behavior and influence the efficacy of EPNs as biological control agents.