Applying Insect Ecology and Behavior to Improve Sustainable Pest Management for Drosophila suzukii

Abstract

The introduction of the invasive vinegar fly Drosophila suzukii (spotted-wing drosophila) to the continental United States substantially disrupted integrated pest management (IPM) in fall-bearing caneberries (raspberries and blackberries). Prior to D. suzukii’s introduction, the caneberry pest complex was primarily composed of plant pathogenic fungi and fruit rot pathogens, with few interventions needed to control insect damage. However, tolerance for D. suzukii larvae in fruit is low, and a lack of management options has necessitated calendar-based insecticide applications, significantly increasing pesticide usage. As part of a larger effort to restore IPM in caneberries, my dissertation aims to advance our knowledge of D. suzukii’s ecology towards more sustainable pest management. Part of this work includes evaluating insecticide spray coverage on diversified fruit farms, with the overarching objective of improving spray coverage in the regions of the caneberry canopy that have the highest D. suzukii activity levels. Optimizing spray coverage may increase the impact and efficacy of each insecticide application, suppressing D. suzukii populations with fewer insecticide applications. Improved spray coverage can also benefit disease management in caneberries. I additionally investigated interactions between D. suzukii and fungal microbes; both yeasts and hyphal fungi interact with D. suzukii throughout its life history, representing weak points that may be exploited for pest management. I tested how different species of yeast impact fitness and feeding behavior in larval D. suzukii and evaluated potential vectoring associations between D. suzukii and fruit rot fungi. Although further work is needed to fully understand D. suzukii’s patterns of microbial resource use, these studies demonstrate that interactions between D. suzukii and fungal microbes have the potential to alter both insect and pathogen pressure. Advancing our understanding of these interactions may facilitate the development of new pest management tactics. For example, yeasts could be used to develop species-specific insecticidal baits or lures for monitoring. Likewise, an epidemiological link between D. suzukii and fruit rot fungi would indicate that improved control of D. suzukii also provides benefits for pathogen management.