Parasitoids (Hymenoptera: Chalcidoidea) of the Cabbage Seedpod Weevil (Coleoptera: Curculionidae) in Georgia, USA
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J. HYM. RES. Vol. 15(2), 2006, pp. 187–207 Parasitoids (Hymenoptera: Chalcidoidea) of the Cabbage Seedpod Weevil (Coleoptera: Curculionidae) in Georgia, USA GARY A. P. GIBSON,MICHAEL W. GATES AND G. DAVID BUNTIN (GAP) Agriculture and Agri-Food Canada, Biodiversity and Integrated Pest Management, K. W. Neatby Bldg., 960 Carling Avenue, Ottawa, ON, Canada, K1A 0C6; email: [email protected] (MWG) Systematic Entomology Laboratory, PSI, Agricultural Research Service, U.S. Department of Agriculture, c/o National Museum of Natural History, Smithsonian Institution, Washington, DC 20560-0168, USA (GDB) Department of Entomology, University of Georgia, Georgia Station, Griffin, GA 30223, USA __________________________________________________________________________________________________________________________________________________________ Abstract.—Five families and 13 species of Chalcidoidea (Hymenoptera) were obtained from mass-reared seedpods of Brassica napus L. (Brassicaceae) as putative parasitoids of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), in Georgia, USA. The species are Conura torvina (Cresson) (Chalcididae), Euderus glaucus Yoshimoto and Necremnus tidius (Walker) (Eulophidae), Brasema allynii (French) n. comb. (from Eupelmus Dalman) and Eupelmus cyaniceps Ashmead (Eupelmidae), Eurytoma tylodermatis Ashmead (Eurytomidae), and Lyrcus incertus (Ashmead), L. maculatus (Gahan), L. perdubius (Girault), Mesopolobus moryoides Gibson, Neocatolaccus tylodermae (Ashmead), Pteromalus cerealellae (Ashmead) and Pteromalus sp. (Pteromalidae). An illustrated key is provided to differentiate the taxa. Lyrcus maculatus constituted about 96% of all reared Pteromalidae and 86% of the total parasitoid fauna. The associations of B. allynii, E. glaucus, E. cyaniceps, E. tylodermatis, L. incertus, N. tylodermae, Pteromalus sp. and P. cerealellae with C. obstrictus are new, but some of these species likely are hyperparasitoids or emerged from insect contaminants of the mass-reared seedpods. The only previous report of a parasitoid of C. obstrictus in eastern North America, Trichomalus perfectus (Walker) (Pteromalidae), is a misidentification. The parasitoid fauna of C. obstrictus in Georgia is discussed relative to that known for western North America. __________________________________________________________________________________________________________________________________________________________ The cabbage seedpod weevil, Ceuto- tera: Chalcidoidea) parasitoids of the cab- rhynchus obstrictus (Marsham) (Coleoptera: bage seedpod weevil in western North Curculionidae), was introduced from Eur- America, including Breakey et al. (1944), ope to western North America about Doucette (1944, 1948), Hanson et al. (1948), 70 years ago. Since then it has become the Carlson et al. (1951), McLeod (1953), Walz most important insect pest of canola and (1957), and Dosdall et al. (in press). rape, Brassica napus L. and B. rapa L. Murchie and Williams (1998) listed 7 (Brassicaceae), in most areas of the conti- identified and 4 unidentified species in 9 nent where these crops are grown (Ca´r- genera and 5 families of Chalcidoidea as camo et al. 2001, Kuhlmann et al. 2002). It parasitoids of C. obstrictus in North Amer- was first reported from eastern North ica, but almost all of the species names America in North Carolina, USA (USDA either represent misidentifications or are 1960), and is now known to extend from now recognized as junior synonyms of Georgia to Quebec and Ontario, Canada older names (Gibson et al. 2005). Dosdall et (Brodeur et al. 2001, Mason et al. 2004). al. (in press) reported another six chalcid There have been several surveys of the species as reared from B. napus and B. rapa introduced and native chalcid (Hymenop- seedpods in Alberta. Consequently, the 188 JOURNAL OF HYMENOPTERA RESEARCH Table 1. Chalcid parasitoids associated with the report of parasitoids of C. obstrictus in cabbage seedpod weevil in North America, including eastern North America. Buntin (1998) for Georgia the number of specimens and percentage (in parenthesis) of total parasitoids reared by Buntin stated that greater than 96% of the para- (1998). sitoids recovered from seedpods of B. napus in Georgia were Trichomalus perfectus Western North (Walker) (Pteromalidae). This species is the Taxon America Georgia most common biological control agent of C. Chalcididae obstrictus in Europe (Murchie and Williams Conura albifrons (Walsh) + – 1998) and was long thought to have been 1 + ? Conura side (Walker) – introduced to North America along with Conura torvina (Cresson) + 9 (0.8) the seedpod weevil. However, Gibson et al. Eulophidae (2005) showed that all previous reports of + Euderus albitarsis – T. perfectus in western North America were (Zetterstedt) Euderus glaucus 2 2 (0.2) misidentifications of Trichomalus lucidus Yoshimoto (Walker), another European species. Necremnus tidius (Walker) + 6 (0.5) Accurate identification of parasitoid spe- Eupelmidae cies is a prerequisite for successful classical Brasema allynii (French) 2 5 (0.5) biological control and integrated pest man- Eupelmus cyaniceps 2 4 (0.4) agement. The senior author examined the Ashmead parasitoids reared by Buntin (1998) as part + Eupelmus vesicularis – of a larger study to document the diversity (Retzius) and identity of the chalcid parasitoids of C. Eurytomidae obstrictus in North America. The primary + Eurytoma tylodermatis 25 (2.2) purpose of Buntin (1998) had been to Ashmead examine the effect of trap cropping on the Pteromalidae number of seedpod weevils and its para- + Chlorocytus sp. – sitoids in canola crops in Georgia. The Lyrcus incertus (Ashmead) 2 6 (0.5) Lyrcus maculatus (Gahan) + 967 (86.0) species identities of the parasitoids had Lyrcus perdubius (Girault) + 60 (5.3) therefore never been thoroughly investi- Mesopolobus bruchophagi + – gated. The purpose of this paper is to (Gahan) provide the first comprehensive informa- + Mesopolobus mayetiolae – tion on the diversity of the chalcid para- (Gahan) Mesopolobus moryoides + 2 (0.2) sitoids reared from canola seedpods in Gibson southeastern USA in order to facilitate Neocatolaccus tylodermae 2 33 (2.9) future studies of the parasitoid fauna (Ashmead) associated with C. obstrictus throughout 2 Pteromalus cerealellae 1 (0.1) North America. (Ashmead) Pteromalus spp.2 + 4 (0.4) Trichomalus lucidus + – MATERIALS AND METHODS (Walker) The chalcid parasitoids identified in this 1 Single record, likely a misidentification of C. torvina study were obtained from mass-reared (see text). seedpods of B. napus collected from the 2 Females in the two regions represent different Bledsoe Research Farm (33u10.6359N species (see text). 84u24.3549W) located near Griffin, Georgia, from 1994–1996, as per ‘‘Material and chalcid fauna purportedly parasitizing C. methods’’ in Buntin (1998). Although not obstrictus in western North America in- stated, the pods were screened for insect cludes at least 14 species (Table 1). In contaminants prior to rearing. Contami- contrast, there is only a single published nants mainly included aphids (Hemiptera: VOLUME 15, NUMBER 2, 2006 189 Aphididae) and larvae and pupae of the using Adobe PhotoshopTM to enhance cla- diamondback moth, Plutella xylostella (L.) rity. (Lepidoptera: Plutellidae). The reared parasitoids had been stored in ethanol, RESULTS but were critical-point dried, point- A total of 1,127 specimens of Chalcidoi- mounted, and identified to genus by the dea were sufficiently intact that they could senior author using the relevant family be identified accurately. Of these, there keys in Gibson et al. (1997). The senior was a single male Pachyneuron aphidis author is responsible for all species identi- (Bouche´) and a female and male Asaphes fications except Eurytoma tylodermatis Ash- suspensus (Nees) (Pteromalidae). Members mead (Eurytomidae), which was identified of Pachyneuron and Asaphes are obligate by MWG. Information concerning the hyperparasitoids of aphids (Gibson et al. method of species identification within 1997) and are not dealt with further. The each genus is provided under the relevant remaining 1,124 specimens included 5 species discussion. Voucher specimens are families, 10 genera, and 13 species of deposited in the Canadian National Col- Chalcidoidea that are possible parasitoids lection of Insects and Arachnids (CNC), of C. obstrictus. These taxa are keyed below Ottawa, Ontario, the University of Georgia and subsequently treated by family in Museum of Natural History (UGCA), alphabetical order. The key also segregates Athens, Georgia, and the United States Trichomalus Thomson and Chlorocytus Gra- National Museum of Natural History ham, the only two genera reared from C. (USNM), Washington, District of Colum- obstrictus in western North America (Dos- bia. Terms used for parasitoid structure dall et al. in press) that were not recovered follow Gibson (1997). Photographs are by Buntin (1998) (Table 1). The two taxa composite serial images that were com- are included in the key because species of bined using Auto-MontageTM.These both genera occur in eastern North Amer- images and the scanning electron micro- ica and may eventually be reared as part of photographs were digitally retouched the regional C. obstrictus parasitoid fauna. KEY TO CHALCIDOIDEA PUTATIVELY PARASITIZING C. OBSTRICTUS IN GEORGIA 1 Hind leg with elongate coxa of similar length to conspicuously swollen and ventrally toothed femur, and with curved tibia (Fig. 1) . Conura torvina