Investigating Beauveria brongniartii abundance dynamics following inoculation treatments: A statistical modeling approach

Abstract: Beauveria brongniartii, a natural antagonist of the cockchafer (Melolontha
melolontha), is employed as a biological control agent to mitigate cockchafer infestations that
pose a threat to European grassland. While a fungal product for controlling infestations in
valleys is available, the challenge persists in developing a dispersion formulation applicable to
steep alpine slopes. As B. brongniartii produces different growth structures depending on the
stage of its life cycle, the aim is to determine which propagule types might be suitable for use
as a virulent active agent in the soil. This is being investigated through previously conducted
pot trials and upcoming field studies, where inoculation treatments containing B. brongniartii propagules are added to the soil and fungal abundance is monitored. Most of the treatments in the pot experiment led to high but fluctuating fungal density over time, which made interpreting results more challenging. Thus, the goal is to design a discrete-time model based on a Ricker model, to help evaluate the development of fungal abundance following the inoculation of different propagules. The model will also assess the impact of factors like temperature which can cause fluctuations in the fungal population while simultaneously accounting for unpredictable variation. Furthermore, prior knowledge gained from the pot experiment will also be included in the model. Finally, it should be possible to determine the suitable propagule type and predict the development of fungal abundance under specific parameter settings.