The Bertha Armyworm can be one of the most destructive pests of canola in Western Canada. They are native to North America and produce one generation per year. 

What Does the County do to Help?

In mid to late June the County monitors the number of insects by placing pheromone traps in five different locations. The traps are checked weekly and the totals from each trap are recorded and sent to Alberta Agriculture. These numbers are used to forecast possible infestations.

With diligent monitoring and scouting, we can lessen the impacts if an outbreak should arise.

What are the Risks?

The larvae are responsible for the damage to canola by defoliating plants as well as eating seed pods. High numbers of larvae can cause complete destruction of a crop in a very short time period. These larvae go through six growth stages from hatching to maturity and cause more damage with each stage.

What to Look For

             Bertha Army Worm pupae                                                Bertha Army Worm  larvae

                              Pupae                                                                             Newly hatched larvae

            Bertha Army Worm  adults                                                 Bertha Army Worm feeding larvae

                              Adults                                                                              Feeding larvae

            Bertha Army Worm  mixed                                                 Bertha Army Worm  trap

                  Mixed Bertha Armyworms                                                           Betha Armyworm trap


There are many ways you may prevent or limit the potential damage armyworms can inflict on canola:

  • Scout fields early to determine the potential of an outbreak
  • Monitor annually to provide an accurate forecasting map for the following year
  • Alternate canola with non-susceptible crops
  • Provide effective weed control of host plants (i.e. stinkweed, lambs quarters, etc.)
  • Use earlier varieties and seed early if possible to have crops more mature at time of moth egg laying
  • Swath earlier when possible
  • Promote the increase of parasitoid insect establishment to provide more natural control

Related Links

Canola Council Bertha Armyworm management

Canola Watch Bertha Armyworm insect Update

Field Scouting for Bertha Armyworm

Build a Bertha Army Worm Trap