Protecting Canada's canola crops from root maggots

Overview

Results

The team

Related information

So what's the problem?

The cabbage maggot, Delia radicum, was introduced from Europe into eastern North America in the 19th century and became significant pest of canola (Brassica napus and B. rapa) in prairie Canada. Injury to canola roots is caused by D. radicum larvae feeding on and in roots of the host plant, disrupting the uptake of nutrients and water, resulting in fewer seeds per plant and reduced seed weight.

Across the Canadian prairie provinces of Alberta, Saskatchewan and Manitoba, the proportion of fields infested and level of injury have both increased since the 1980s. The expansion of Delia cabbage maggots into canola necessitates a re-evaluation of its biological control.

The introduction of parasitoids from Europe, where the D. radicum of North America originated, to improve control has been suggested for integration with existing management strategies and the most promising species for introduction is Aleochara bipustulata. The adult beetles feed on cabbage maggot eggs and larvae, and its larvae parasitize cabbage maggot puparia.

What is this project doing?

The objectives of this project are to:

Assess the prey types of the adult stage of Aleochara bipustulata
Investigate interactions of Aleochara bipustulata with other natural enemies of cabbage root maggot

Collaborative research by the University of Manitoba, AAFC and CABI focused on the role A. bipustulata may play in North American ecosystems if it is introduced as a classical biological control agent against D. radicum. To investigate whether A. bipustulata and other members of the natural enemy complex of D. radicum will complement one another and reduce D. radicum survival, the egg consumption of A. bipustulata was tested in the presence of one or two additional egg predators.

Currently, we are assessing the prey types of adult A. bipustulata under field conditions and continue investigating the direct and indirect competitive interactions between A. bipustulata and other Delia predators.

Results so far

The results of our comeptition experiments indicate that the level of predation on Delia eggs indeed increases with numbers of predators present. The types of prey which were consumed by A. bipustulata during laboratory feeding trials were mainly third instar larvae of D. radicum, oligochaetes, and occasionally mites, Collembola, and aphids.

You may be interested to refer to our book 'Biological Control Programmes in Canada 1981-2000', which is published by CABI.

Project Executive