The parasitoid communities associated with an invasive canola pest, Ceutorhynchus obstrictus (Coleoptera: Curculionidae), in Ontario and Quebec, Canada

Abstract

AbstractSurveys were conducted to determine the parasitoid communities associated with the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), an important invasive pest of canola in Ontario and Quebec, Canada. More than 18 species of Chalcidoidea (Hymenoptera) were associated with this pest through mass rearings from canola siliques. In southwestern Ontario, the most abundant species were a species of Chlorocytus Graham (23.6%–48.6%), Lyrcus perdubius (Girault) (0%–53%), L. maculatus (Gahan) (2.8%–14.7%), and species of Pteromalus Swederus (0.6%–23.1%) (Pteromalidae). In contrast, the most abundant species in Quebec were Trichomalus lucidus (Walker) (Pteromalidae) (33.3%–56.4%), unidentified Eulophidae (2.1%–39.1%), Mesopolobus gemellus Baur and Muller (Pteromalidae) (1.3%–21.4%), and Necremnus tidius (Walker) (Eulophidae) (11.5%–19.3%). In the Ottawa, Ontario, area, parasitoids were first recovered in 2008, and Trichomalus perfectus (Walker) (Pteromalidae), M. gemellus, and species of Pteromalus were most prevalent. Mesopolobus gemellus and T. perfectus are reported in North America for the first time. Although existing communities appear to provide substantial parasitism (e.g., 6.3%–26.3% in 2006), species composition varies among years and differs from that in other regions in North America. Thus, parasitism levels and parasitoid communities of the cabbage seedpod weevil should be monitored to assess whether these will increase or there is a need to introduce more host-specific species from Europe that could provide greater mortality.