Survey of Trichogramma (Hymenoptera: Trichogrammatidae) Natural Populations in Quebec Cranberry Bogs and Identification Using rDNA ITS-2 Sequence Analysis

Abstract

The province of Quebec, Canada is the most important organic cranberry growing region worldwide. However, insect pest management methods are limited, and growers face significant yield loss each year, mostly caused by lepidopteran pests. Egg parasitoids of the genus Trichogramma (Hymenoptera: Trichogrammatidae) are effective biocontrol agents of lepidopteran pests in many forests and agricultural systems. Herein, a two-year, large-scale population survey of Trichogramma spp. was performed using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) as sentinel eggs in Quebec organic cranberry bogs. Collected specimens were identified by sequencing ribosomal DNA of the Internal Transcribed Spacer 2 (ITS-2) region and subjected to resemblance analysis with reference specimens for identification. Our results confirm that at least four Trichogramma species naturally occur in the studied agroecosystem. Those species are T. brassicae Bezdenko, T. minutum Riley, T. ostriniae (Pang et Chen), and T. pretiosum Riley. While some species have already been reported in cranberry bogs, this represents the first mention of T. brassicae and T. ostriniae as well as the first mention of T. minutum in Quebec cranberry bogs. All species collected are native from Eastern Canada except T. ostriniae. These species can be considered as biocontrol agent candidates for cranberry lepidopteran pests, but further efficacy trials are needed to identify the best species for each pest.

Keywords: Lepidoptera; biocontrol agent; egg parasitoid; molecular identification; native species.