Diamondback moth, Plutella xylostella Linnaeus (Lepidoptera: Plutellidae) is a globally distributed pest on brassicaceous crops. This study aimed to follow up with aspects of earlier research, mainly to revisit the potential for overwintering of diamondback moth in the Ottawa area, to investigate present day population dynamics using a life-table approach and to use next generation sequencing to describe the diamondback moth microbiome. A review of the literature has reaffirmed that diamondback moth may not be capable of overwintering in Ottawa with populations likely migrant-driven. The population dynamics and parasitoid community appear to be unaltered after 65 years. The microbiome of diamondback moth larvae was dominated by Enterococcaceae, a family of bacteria hypothesized to aid in resistance and detoxification. This can provide opportunities for the introduction of new biological control agents and tools for diamondback moth management in the future.