Outcome of Biological control of Delia sp. in cole crops with rove beetles, Aleochara sp. Part1)

The results of this study demonstrated that Aleochara sp. beetles were present in both organic and conventional cole crop fields, in southwestern British Columbia. 301 Staphylinid beetles were captured in pitfall traps over the course of 14 weeks from June to early September. Of these 59 have been tentatively identified as belonging to the genus Aleochara. The native population of Aleochara beetles does have some impact on the D. radicum population, as was demonstrated by parasitism of overwintering pupae. More rove beetles, in general, were trapped in the grass margins around fields than in tree/shrub margins or within the field.

Although this project was intended as a specific study of Aleochara sp. we also considered rove beetles in general. This seems reasonable given that rove beetles are known to be generalist predators, although Aleochara bilineata is the most studied for purposes of root maggot biological control. The other Staphylinid genera and species present in the fields studied most likely contribute to the predation of D. radicum eggs and young larvae. Some of the genera similar in size and lifecycle to Aleochara sp. may also parasitize D. radicum pupae.

In small scale field trials mulching around plants with grass-clippings was shown to increase the presence of native rove beetles within the field. Introductions of A. bilineata helped to reduce the number of cabbage maggots infesting plants, in small field cage experiments. Both these techniques will be explored on a larger scale to further assess their operational feasibility and cabbage maggot control potential.