Surviving the greenhouse Thrips biocontrol, antipredator behaviours and plant-mediated interactions

The objectives of this thesis were to review the existing literature on predatory soil mites and alternative food sources in biocontrol systems, identify a suitable natural predator for controlling invasive thrips species Echinothrips americanus and Thrips parvispinus, and investigate the role of increased soil biodiversity in shaping plant phenology traits.
The thesis starts with an overview of below-ground biocontrol systems using predatory soil mites to manage pests in the soil with the aim to consolidate existing studies, emphasizing the potential of these natural enemies which have had limited research in this area. Since the focus of the thesis is biological control, I next focused on the role of alternative food for natural enemies and its effects on predator and pest populations. Using a meta-analysis approach, I revealed that introducing natural enemies before pests and providing alternative food can enhance long-term biocontrol effectiveness.
Moving towards the experimental chapters of the thesis, I started by testing predatory mites to control thrips on various plants and showed promising results for controlling T. parvispinus with certain predatory soil mites. Since biocontrol of E. americanus was not successful, I explored thrips' antipredator behaviours, which might hinder predator success. Echinothrips americanus displayed these behaviours most frequently of all the thrips investigated, making it challenging for predatory mites to prey on them.
Lastly, I investigated the effects of increased soil biodiversity on plant performance, showing improved plant performance under suboptimal fertilization conditions when adding the predatory soil mite S. scimitus and its associated soil biota.