Brassica Vegetables Insecticides Insects Pest Management Research

Got cabbage maggots? We’re interested!

Laura Stortz, OMAFRA / University of Guelph USEL student; Denise Beaton, OMAFRA Crop Protection Program Lead; Hannah Fraser, OMAFRA Entomology Program Lead (Hort)

The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) is collecting Cabbage Maggot larvae and pupae this summer as part of a national survey. We need grower cooperators for this survey! The goals of this survey are:

  1. To better understand the fly species responsible for damage to Brassicae vegetable crops.
    The larval stage of the Delia radicum fly species is thought to be the main culprit attacking Brassicae vegetable crops; however, there could be other species at play.
  2. Test for pesticide resistance in the fly species.
    Cabbage maggot is showing resistance to Lorsban (chlorpyrifos). This study’s results could lead to more efficient use of insecticides and support research on alternative control options.


Cabbage maggot, Delia radicum, is a serious pest of Brassicae vegetable crops, such as broccoli, cabbage, rutabaga, cauliflower, Chinese cabbage, radishes and other vegetables in the cabbage family. The larvae of the cabbage maggot will attack seedling roots of cabbage, broccoli, cauliflower, Brussels sprouts and other Cole crops, causing loss of crop vigour and an entry point for secondary soil-borne pathogens. For rutabagas, the larvae will also tunnel into the developed root making it unmarketable.

The first generation is the most active and most damaging. It occurs from mid-May through June when yellow rocket is flowering. A second generation occurs in mid-July, which coincides with the flowering of day lilies. There is also a third generation that is in late-August when goldenrod is flowering. The second and third generations can also cause significant damage to rutabagas.

OMAFRA needs grower cooperators for this survey to be a success!

To participate in this important national survey, you need:

  • To be a grower of cabbage, broccoli, cauliflower, Brussels sprouts or other Cole crops
  • To contact Hannah Fraser, OMAFRA’s Entomologist (Horticulture Program Lead) at (519) 824-4120 x52671 or to express your interest in participating in this survey.
  • To provide OMAFRA with the location of your Brassicae vegetable fields that can be scouted for larvae and pupae of the suspected Cabbage Maggot.

Results of this survey will be shared with the grower cooperators. We hope to hear from you soon, since the first generation of cabbage maggot is already occurring in parts of Ontario.

Flowering yellow rocket
Flowering yellow rocket

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