Dosdall: Integrated Management of the Cabbage Seedpod Weevil and Overwintering Biology of Canola Pests
Date: June 2004
Term: 3 years
Status: Completed
Researcher(s): Dr. Lloyd Dosdall, Department of Agricultural, Food and Nutritional Science, University of Alberta
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: Canola Council of Canada, ACPC, MCGA
Project Summary
Three years of study have been completed toward developing an integrated management strategy of cabbage seedpod weevil, and to determine aspects of the overwintering biology of lygus bugs and cabbage seedpod weevil. Study results show that growers in regions infested annually with high populations of cabbage seedpod weevil should avoid seeding crops quite early in season because they are highly attractive to these pests at that time. Also, trap cropping can enable growers to reduce their costs, limit insecticide use, and can therefore enhance environmental sustainability.
A three-year study conducted in Alberta in 2001, 2002 and 2003 provides information toward developing an integrated management strategy of cabbage seedpod weevil, and to determine aspects of the overwintering biology of lygus bugs and cabbage seedpod weevil. The study has important implications for the canola industry in western Canada.
Larva of the Cabbage Seedpod Weevil in a Canola Pod
Source: L. DosdallStudy results confirmed that manipulation of canola seeding rates and seeding dates affected infestations of cabbage seedpod weevil. Growers in regions infested annually with high populations of cabbage seedpod weevil should avoid seeding crops early in the season because they are highly attractive to these pests. The study showed that infestations were greatest at high seeding rates of 4.5 lb/acre (5 kg/ha) and when seeding occurred in early May compared with later in May. However, seed yields were still greater at higher seeding rates; therefore maintaining relatively dense canola plant stands are recommended.
Planting borders of early-flowering canola around crops that flower later was successful in concentrating weevils on field edges. This then facilitated applications of insecticide on the trap crops, without requiring treatment of entire canola fields. Trap cropping can enable growers to reduce their costs, limit insecticide use, and can therefore enhance environmental sustainability.
Adult of the Cabbage Seedpod Weevil on Canola Pod
Source: L. DosdallTree shelters were more suitable overwintering habitats for cabbage seedpod weevils than other sites evaluated, including fields and adjacent headland or margin areas. Lygus bugs survived equally well in both field and adjacent headland or margin areas that were dominated by shelterbelt or poplar tree species. Lower temperatures in the soil in open fields can explain the higher numbers of insects in the treed habitats, where temperatures are higher in those habitats. The survivorship of cabbage seedpod weevils for extended overwintering periods (18 weeks) suggests these insects are capable of surviving in more northern latitudes. Temperature data from overwintering microclimates will be used to refine models to assist in predicting potential pest infestation potential and range expansion.
The study also included host plant resistance research and has determined that genetic sources of resistance to infestation by cabbage seedpod weevil exist within Brassicaceae. Of the species evaluated, Crambe abyssinica, Sinapis alba, Brassica nigra, and Brassica carinata are most resistant to attack by this pest. The resistance in C. abyssinica to attack by the weevil cannot be crossed with B. napus; however, resistance in S. alba, B. carinata, and B. nigra are of considerable interest because these species can now be used as sources of resistance in breeding programs to develop weevil-resistant canola. Germplasm development research has been initiated to incorporate resistance genes from these species into elite genotypes of B. napus. The results will be used to develop gene mapping populations for facilitating transfer of resistance genes to commercial canola varieties.
In this study, researchers also found hymenopteran wasp parasitoids in southern Alberta that attack both the adult and larval stages of cabbage seedpod weevil. The adult weevil endoparasite, Microctonus melanopus, has been found at several sites throughout southern Alberta, and approximately 13 species of weevil larval ectoparasites have also been discovered. Currently the weevil parasitoid fauna is not sufficiently abundant to cause substantial reductions in cabbage seedpod weevil infestations; however, our research suggests that numbers have been increasing over the past three years and eventually they may represent important limiting factors on cabbage seedpod weevil populations. The weevil larval ectoparasitoid fauna is currently comprised of species endemic to North America, and until the potential impact of this fauna on cabbage seedpod weevil populations is determined, it is premature to consider parasitoid introductions from Europe.
Scientific Publications
Dosdall, L.M., and D.W.A. Moisey. 2004. Developmental biology of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Coleoptera: Curculionidae), in spring canola, Brassica napus, in western Canada. Annals of the Entomological Society of America 97: 458-465.
Dosdall, L.M., and M.A. McFarlane. 2004. Morphology of the pre-imaginal life stages of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae). The Coleopterists’ Bulletin 58: 45-52.
Kalischuk, A.R., and L.M. Dosdall. 2004. Susceptibilities of seven Brassicaceae species to infestation by the cabbage seedpod weevil (Coleoptera: Curculionidae). The Canadian Entomologist 136: 265-276.
Fox, A.S., S.R. Shaw, L.M. Dosdall, and B. Lee. 2004. Microctonus melanopus (Ruthe) (Hymenoptera: Braconidae), a parasitoid of adult cabbage seedpod weevil (Coleoptera: Curculionidae): Distribution in southern Alberta and female diagnosis. Journal of Entomological Science 39: 350-361.
Cárcamo, H.A., R. Dunn, L.M. Dosdall, and O. Olfert. 2007. Managing cabbage seedpod weevil in canola using a trap crop – a commercial field-scale study in western Canada. Crop Protection 26: 1325-1334.
Cárcamo, H.A., C.E. Herle, J. Otani, and S.M. McGinn. 2009. Cold hardiness and overwintering survival of the cabbage seedpod weevil, Ceutorhynchus obstrictus. Entomologia Experimentalis et Applicata 133: 223–231.