Spotted wing Drosophila (SWD), an invasive insect pest, lays its eggs in berries and other small fruits causing them to rot. In BC, ~25% of SWD harbor an intracellular symbiotic bacterium, called Wolbachia- implicated in protecting insect hosts against RNA viruses. There are currently no effective, specific, or environmentally friendly tools to manage this pest and finding control strategies is a top priority for BC’s berry industry. The goal of this project was to advance the study and development of microbial biopesticides, which represent an untapped source of specific and environmentally sustainable control agents.
Through next-generation sequencing technologies, seven RNA viruses and two DNA viruses that are new for SWD were discovered. These represent exciting potential candidates for SWD control, and include a DNA virus in the nudivirus family, relatives of which have been successfully used to control other insect pests.
Using controlled fitness experiments, Wolbachia frequencies in SWD were found to change very rapidly depending on environmental conditions, suggesting that they strongly impact their hosts. Wolbachia was also found to protect BC SWD against pathogenic RNA viruses; which is important to consider when pursuing viral control strategies.
Next, experimental evolution and sequencing experiments using Drosophila C virus indicated that viruses which evolved in the presence of Wolbachia were significantly more pathogenic to Wolbachia-free individuals and acquired a number of new mutations.
An unanticipated outcome of this project was the discovery of two parasitoid wasp natural enemies of SWD that appear to be responsible for causing significant mortality of the pest in diverse habitats in BC. This self-sustaining biological control has the potential to markedly reduce the need for insecticide applications against SWD.
In summary, the identification of several naturally occurring viruses of SWD and the significant progress in understanding the role of Wolbachia in SWD in BC will help form a foundation for the development of biopesticides to help fruit growers combat this invasive agricultural pest.