Holliday: Classical Biological Control of Root Maggots

Date: November 2003
Term: 3 years
Status: Completed
Researcher(s): Dr. N.J. Holliday, Department of Entomology, Faculty of Agriculture and Food Sciences, University of Manitoba
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: Canadian Commonwealth Scholarship and Fellowship Office, the Agricultureal Research and Development Initiative of the Manitoba Association of Agricultural Societies, CCC, AAFC, Entomological Society of Canada

Project Summary

The effect of root maggots feeding on canola roots has not been fully quantified, but it is clear that large numbers of maggots reduce yield, and can cause plant death. No insecticides are available to control root maggots in canola, so this project focused on the potential for using classical biological control of cabbage root maggots in canola on the Canadian Prairies and to begin detailed studies on them. After comparing parasitoids in Europe and Canada, the European Aleochara bipustulata was selected as a promising candidate for introduction to Canada for classical biological control of root maggots.

Throughout the last four decades there has been a steady increase in root maggots in prairie canola, and since the 1980s, there has been significant crop damage in Alberta. At the time of the study, economic damage had not been reported in Saskatchewan and Manitoba, but the increasing trend is beginning to show potential of economic loss in Manitoba.

Aleochara attacking cabbage maggot puparium.

Source: K. RileyThe effect of root maggots feeding on canola roots has not been fully quantified, but it is clear that large numbers of maggots reduce yield, and can cause plant death. Adult cabbage root maggots are similar to a housefly, but greyish and smaller. Female flies lay eggs near the base of canola stems. The eggs hatch into legless, headless maggots that browse on the roots, producing surface grooves and later tunnels in the root. Rotting of root tissues frequently results. After repeated molting and feeding, the mature maggot swells into a brown barrel-like resting stage. It over-winters in this stage and the following spring adult flies emerge and search for mates.

No insecticides are available to control root maggots in canola because the vulnerable maggot stage occurs in mid-July. Insecticidal seed treatments that would be active in July are too persistent to be used. Research is being done to find non-insecticidal control methods. This project focused on the potential for using classical biological control, and the objective was to identify candidate agents that could be used in classical biological control of cabbage root maggots in canola in prairie Canada and to begin detailed studies on them.

Aleochara bipustulata adults and cabbage maggot larva.

Source: L. AndreassenIn this three-year study, researchers compared principle parasitoids of root maggots in Europe and Canada to determine if any would be suitable for introduction to Canada. In canola in the Canadian Prairies, the principle parasitoids of root maggots are Trybliographa rapae, Aleochara bilineata and Aleochara verna. In canola in Europe, the principle parasitoids of root maggots are Trybliographa rapae, Aleochara bilineata and Aleochara bipustulata. Studies of records and specimen collections revealed that there is no evidence of A. bipustulata occurring in North America.

After comparing parasitoids in Europe and Canada, the European A. bipustulata was selected as a potential candidate for introduction to Canada for classical biological control. A literature search provided further evidence that A. bipustulata shows promise as a biological control in Canada. The species is well adapted to northern climates with short growing season and prairie-like photoperiodic regimes. In Northern Europe, A. bipustulata is able to attack root maggots earlier in the season than A. bilineata.

The results of this study also provided information about the biology of the cabbage root maggots in canola in the Canadian Prairies. Within the range of 16 to 21 weeks, there is no effect on emergence or survival of root maggots of the duration of cold exposure required by diapausing or resting stage root maggot pupae. In prairie canola, root maggots emerge later in the season than in most other systems studied, which indicates that any parasitoids selected for introduction must come from populations that can accommodate this late emergence.

This information will be useful in selecting appropriate European populations of A. bipustulata for introduction into Canada as classical biological control for root maggots. A. bipustulata should receive intensive study as it is a promising candidate for introduction for biological control of cabbage root maggots in canola in the Prairie Provinces of Canada.

Scientific Publications

ANDREASSEN LD, KUHLMANN U, WHISTLECRAFT JW, SOROKA JJ, MASON PG, AKINREMI OO & HOLLIDAY NJ. 2010. Spring emergence of Canadian Delia radicum (Diptera: Anthomyiidae) and synchronization with its natural enemy, Aleochara bilineata (Coleoptera: Staphylinidae). Canadian Entomologist 142: 234–249.

ANDREASSEN LD, KUHLMANN U, MASON PG, HOLLIDAY N.J. 2009.Host range testing of a prospective classical biological control agent against cabbage maggot, Delia radicum, in Canada. Biological Control 48: 210–220.

ANDREASSEN LD, KUHLMANN U , MASON PG, HOLLIDAY NJ. 2007. Classical biological control of the cabbage root fly, Delia radicum, in Canadian canola: an analysis of research needs. CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 2007, 2, No. 086, 13 pp, http://www.cababstractsplus.org/cabreviews.

HEMACHANDRA KS, HOLLIDAY NJ, MASON PG, SOROKA JJ & KUHLMANN U. 2007. Comparative assessment of the parasitoid community of Delia radicum in the Canadian prairies and Europe: a search for classical biological control agents. Biological control. 43: 85–94

HEMACHANDRA KS, KUHLMANN U, MASON PG, & HOLLIDAY NJ. 2007. Spatial patterns of Trybliographa rapae parasitism of Delia radicum larvae in oilseed rape and cauliflower. Journal of applied entomology 131: 338–346

RILEY KR, KUHLMANN U, MASON PG, WHISTLECRAFT J, DONALD LJ & HOLLIDAY NJ. 2007.Can mustard seed meal increase attacks by Aleochara spp. on Delia sp. in oilseed rape? Biocontrol Science and Technology 17: 273–284

HEMACHANDRA KS, HOLLIDAY NJ, KLIMASZEWSKI J, MASON PG & KUHLMANN U 2005. Erroneous records of Aleochara bipustulata (Linnaeus), (Coleoptera: Staphylinidae), from North America: an assessment of the evidence . The Canadian Entomologist 137: 182–187

Full Report PDF: Classical Biological Control of Root Maggots