Touray et al. Tri-trophic Interactions of Sancassania polyphyllae with Fungal Biocontrol Agents.csvTri-trophic Interactions of soil mite Sancassania polyphyllae (Acari: Acaridae) with Fungal Biocontrol Agents

Mycophagous invertebrates can significantly impact the efficacy of fungal biocontrol agents, yet the interaction between these agents and Sancassania polyphyllae (Acari: Acaridae), commonly found in soil ecosystems, remains poorly understood. Our study demonstrates that S. polyphyllae mites feed on fungus-infected insect cadavers as well as the mycelium and spores of Trichoderma afroharzianum and Metarhizium brunneum in pure cultures. Mite feeding activity was greater on Trichoderma than Metarhizium pure cultures, possibly due to Metarhizium's acaricidal effects, which impacted mite activity. Furthermore, mite feeding on fungus-infected insect cadavers caused visible damage to the integument. This feeding behavior significantly impacted fungal sporulation, a key factor in biocontrol efficacy. In both the M. brunneum-infected Galleria groups and the T. afroharzianum-infected Galleria groups, mite numbers increased over time, peaking around 9 to 11 days post-infection (dpi) before slightly declining or plateauing. Notably, the fungi-infected insect tissue consistently exhibited significantly higher mite numbers than the pure cultures group at several time points. In dual-culture assays, S. polyphyllae mites preferentially fed on Fusarium oxysporum over T. afroharzianum. The presence of Fusarium may influence mite behavior and potentially reduce their impact on Trichoderma. This preference, possibly nutritional, requires further investigation. Consequently, Trichoderma's suppression of Fusarium in soil could significantly impact the food resources available to soil-dwelling mites like S. polyphyllae. Further research is needed to determine the nutritional basis of this feeding preference.