Bertha Armyworm Map - Cumulative Moth Counts

During the Provincial Bertha Armyworm Monitoring Program, pheromone-baited traps are used to monitor male moths (adults) of bertha armyworm. The monitoring program typically begins in early June and continues until early August. Data from the monitoring program is used to develop the Bertha Armyworm Map of Cumulative Moth Counts, which is updated regularly during the monitoring program. The map displays the cumulative male moth counts reported from traps at more than 250 locations in Saskatchewan. The map is intended to display risk on a regional basis. It is critical to use economic thresholds and monitor at the field level for bertha armyworm larvae to determine if control measures will be necessary. Keep in mind that there have been situations where high populations of moths in traps have not corresponded to high numbers in adjacent fields.

Peak emergence of bertha armyworm adults typically occurs mid-July. Once adults have emerged, egg laying occurs soon after. Eggs take an average of 7 days to hatch. Scouting for bertha armyworm larvae should begin at the early podding stage and continue until swathing. In 2024 and 2023, trap catches were low, though moderately higher in 2024 than in 2023. We have seen an increase in catches in 2025 and will continue to monitor until early August. Regional bertha armyworm outbreaks tend to last for two to three years, with eight to 10 years between. The last year with significant infestations was 2013, with minor outbreaks in 2016.

High weekly counts reported during the 2025 monitoring program have resulted in some areas of the province being in the high infestation risk category. In 2025, peak emergence of bertha armyworm occurred during mid-July. The map will be updated weekly until early August. Please note, the coloured points indicate trap catches for individual sites. This information is used to develop the contour map that represents an estimate of regional prevalence, which is why mapping zones extend past the general area of monitoring sites.

Generally, cruciferous crops such as canola and mustard are at risk from bertha armyworm. However, other crops, including flax and quinoa, can be impacted.

Emergence of bertha armyworm moths is highly dependent on temperature. Moths start to emerge in some areas mid-June with peak emergence about mid-July. Adult emergence precedes egg laying, so it can be considered a warning that the destructive larval stage will be present shortly.

When scouting for eggs, there can be differences between canola cultivars. Research has noted that Bertha armyworm egg-laying varied substantially among different species of Brassica. In some cultivars, the number of eggs was high but larval damage was limited. Plants in full flower had the highest number of eggs compared to the pre-flower and podding stages.

General recommendations for observed moth numbers (from pheromone traps):

• 0 to 300 = low risk; control measures unlikely in most cases.
• 300 to 900 = uncertain, most variability for this level; periodic monitoring of fields to verify actual numbers of larvae (especially bolting fields) is required.
• 900 to 1,200 = moderate risk; check for larvae and evidence of damage.
• 1,200 to 1,500 = high risk; monitor fields more frequently.

The Ministry of Agriculture monitors for insects through a network of co-operators across Saskatchewan that provide numbers of adult bertha armyworm moths captured in pheromone-baited traps. Each trap contains an artificial pheromone that mimics the natural bertha armyworm female attractant. Co-operators include producers, Regional Crops Specialists, researchers and industry agronomists.

For information on bertha armyworm and economic thresholds refer to our Bertha Armyworm webpage.