Multiple stressor effects on biological pest control; improving efficacy in challenging environments.

Competing demands for agricultural productivity and sustainability have led to microbial biopesticides emerging as an integral crop protection tool. Developing microbial control in truly integrated pest management programmes, both in managed glasshouse and open agronomic systems with variable environmental conditions, presents scientific challenges. A better scientific understanding of fundamental interactions occurring between microbes and pesticides in combination is needed to ensure safe and effective future use. This includes the impact of interactions on microbial efficacy towards target organisms and whether sensitivities to other stressors are affected in non-target organisms, all within complex biotic and abiotic environments.

Recent studies have investigated translation of mixture toxicity models from ecotoxicology to invertebrate pathology and this project will further our ability to describe how pathogens interact, by utilising novel experimental designs and data analysis. The aim is to detect and understand synergism, antagonism or additivity in terms of pest suppression, to improve reliability and resilience of microbial pest control through combination designs with other chemical inputs for control of weeds, pests and disease to maximise effects.

The student will investigate how underpinning ecological interactions between co-infecting microbial insect pathogens and other toxicants affect the severity of disease, pathogen fitness and the impact on potential for control of pest insects. This will provide key understanding currently lacking for improving the efficacy of biological control in an applied situation.

The overarching aims of the project are to; i) identify where, and how, pathogen/chemical effects combine most effectively and ii) understand how multiple stressors will impact on combination effects under variable environments.

The "test bed" for these aims is an exemplar crop (tomatoes) and pest (whitefly/thrips) system for a series of experiments of increasing complexity. Work in Yr1 will be highly controlled microcosm experiments, allowing accurate manipulation, significant data generation and early peer reviewed publication. In Yr2, mesocosm and initial field trials will test predictions from Yr1 results. Expanding to Y2/3, field trials (glasshouse work significantly supported by the CASE partner) and additional experiments will validate predictions in more complex systems. Multiple glasshouse facilities will allow the student to undertake sequential field trials, thus reducing delivery risk. Specific questions the student will address are;
1. What are key aspects of binary pathogen/chemical mixtures that influence the likelihood of synergism occurring? How are outcomes altered by factors such as dose, strain and timing of application?
2. What are the trade-offs in communities between pathogens in mixed interactions in terms of host mortality, fitness costs and ability to secondary cycle in the host population?
3. How do environmental biotic/ abiotic stressors affect microbial impacts on target hosts and non-target naturally occurring regulating pathogens in the ecosystem?

The innovative link of approaches from ecotoxicology to invertebrate pathology, coupled with expertise of the CASE and project partner in applied biological control worldwide will bring an exceptional level of training and research prospects in: invertebrate pathology, ecotoxicology, parasitology, molecular techniques, modelling and ecology.