“Investigating the impacts of parasitism on herbivory & chemical communication in an insect herbivore”

Introduction: Acalymma vittatum [Fabricus], the striped cucumber beetle (SCB), is a common agricultural pest to the cucurbit plant family. A. vittatum produce an aggregation pheromone- vittatalactone –primarily emitted by male SCB. Vittatalactone production can recruit both male and female SCB to engage in collective feeding and mating behaviors. One natural enemy, however, a parasitoid tachinid fly, Celatoria setosa (Colliquet), has been shown capable of parasitizing 40% or more of a SCB population in the field. Despite high rates of parasitism, we know very little about the impacts C. setosa can have on the behavior of A. vittatum. No previous knowledge has been recorded on the host-prey interactions between the SCB and its major natural enemy. Understanding how parasitism may influence the host behavior in terms of herbivory and chemical communication may provide new information in controlling insect herbivores for integrated pest management. Methods: Vittatalactone was collected and quantified utilizing head space volatile collections with 6-8 parasitized and non-parasitized male SCB. A 2×1 factorial bioassay measuring herbivory leaf damage was performed with parasitized and non-parasitized female SCB, and leaf damage in was measured every 2-3 days on ImageJ software for 12 days. Results:  Parasitized beetles consumed significantly less leaf tissue than non-parasitized beetles over 12 days. Parasitized beetles deposited few to no eggs compared to non-parasitized beetles. Parasitized beetles produced less vittatalactone than non-parasitized beetles, however more replicates need to be completed.