Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2022-2023)

Predicting the threat of disease epidemics and mitigating their impacts is the underpinning of disease ecology. To this end much can be learned from systems in which pathogens and hosts can be easily manipulated. This is the case for many pathogens of insects. Here I propose three research objectives to determine the consequences of variation within pathogen populations, interactions among pathogens and the role of the host microbiome on disease prevalence and transmission in two insect systems; natural populations of western tent caterpillars and laboratory populations of cabbage loopers. Molecular techniques increasingly allow the identification of genetic variants of pathogens and the detection of multiple pathogen species in the same host. This allows exploration of how genetic variability of pathogens, such as viruses, influences their virulence and transmission. Mixed infections of insect viruses produce higher host mortality, but we do not know whether this also means greater transmission to the population. Field experiments can be used to measure disease transmission and impacts on host populations. Secondly I will investigate the influence of competition between different pathogens and whether multiple infections could benefit microbial control of insect plant pests by potentially having synergistic effects, or whether competition between the pathogens reduces their effectiveness. Finally I will explore the interactions between the insect gut microbiota and resistance of the host to pathogens. Recent work indicates that the host microbiome can influence the impact of pathogenic organisms but it is not clear what direction these interactions will go in. Observations of field collected insects and manipulations of their gut microbiota will determine if microorganisms might interact to modify the virulence of pathogens and the immunity of hosts and the costs and benefits of this. By elucidating the impacts of variable pathogens, hosts, and microbial communities, it is possible to develop a detailed understanding of disease dynamics in these two model systems. This will lead to recommendations of how pathogens can be used more effectively to enhance and prolong the efficacy of insect microbial control, and a greater knowledge of the role of pathogens in the regulation of field populations of Lepidoptera.