Species composition and incidence of cabbage seedpod weevil parasitoids in Georgia, U.S.A.

摘要

Parasitoid species composition and incidence of the cabbage seedpod weevil (Ceutorhynchus obstrictus Marsham (Coleoptera: Curculionidae) was examined in winter canola (Brassica napus L.) during 1994-1996 in Georgia, USA. Canola seedpods were collected weekly during the larval development period and held in the laboratory to rear parasitoids. Five families and 13 species of Chalcidoidea (Hymenoptera) were reared from cabbage seedpod weevil samples over the 3-year period. Lyrcus maculatus (Gahan) was the most prevalent species comprising about 86% of total parasitoid fauna. This species plus three others,Lyrcus perdubius (Girault), Neocatolaccus tylodermae (Ashmead) and Eurytoma tylodermatis Ashmead (Eurytomidae), account for over 96% of the total parasitoid fauna. Ceutorhynchus obstrictus represented a new host record for eight parasitoid taxa including N. tylodeermae and E. tylodermatis. The only previously reported parasitoid of C. obstrictus in eastern North America,Trichomalus perfectus (Walker), is erroneous because of misidentification. Only six of the 13 parasitoids also are reported to parasitize C. obstrictus in western North America. The most common species in Georgia, L. maculatus, is only an incidental parasitoid of C. obstrictus in western North America. Conversely, two common parasitoids in western North America, Necremnus tidius (Walker) and Mesopolobus moryoides Gibson, were incidental parasitoids of C. obstrictus in Georgia.