Risk Forecast for Bertha Armyworm in Manitoba in 2022

The population of adult moths of bertha armyworms are monitored using pheromone-baited traps during the flight and egg-laying period. The monitoring period extends from about mid-June through July (June 5 to July 30 in 2022).

The cumulative moth counts from the traps, which are presented in the table below, can not predict what the level of larvae will be in the field a trap is in, but can be used, in conjunction with counts from other traps in a region, to determine areas of the province at higher risk and where increased monitoring of fields for larvae may be necessary. 

Figure 1. Trap for monitoring bertha armyworm.     Figure 2. Bertha armyworm moths.

Phermone-baited traps to monitor adult moths of bertha armyworm were set up in 51 locations in Manitoba in 2022. 
  • Counts remained in the low risk category in all traps.
  • The highest cumulative trap count was 209 from a trap near Durban in Northwest Manitoba. The highest counts were generally fom the western regions of Manitoba. 

Table 1. Highest cumulative counts of bertha armyworm moths from five agricultural regions of Manitoba as of July 30, 2022.

 0-300=low risk   300-900=uncertain risk   900-1,200=moderate risk   1,200+=high risk
Location Count Risk
Durban 209 Low
Bowsman 101 Low
Bowsman 97 Low
Inglis 73 Low
Glenboro 141 Low
Oakburn 101 Low
Decker 87 Low
Miniota 82 Low
Belmont 48 Low
Emerson 34 Low
Baldur 31 Low
Altona 28 Low
Beausejour 14 Low
Stead 14 Low
Hadashville 14 Low
Whitemouth 10 Low
Arborg 17 Low
Arborg 3 Low


Interpreting Bertha Armyworm Cumulative Moth Counts
·       The following table relates the cumulative moth counts over the trapping period with the risk of larval infestation.
Cumulative number of Moths / Trap

Larval Infestation Risk Level

Low - Infestations are unlikely to be widespread, but fields should be inspected for signs of insects or damage.
Uncertain - Infestations may not be widespread, but fields that were particularly attractive to egg-laying females could be infested. Check your fields.
Moderate - Canola fields should be sampled regularly for larvae and for evidence of damage.
High - Canola fields should be sampled frequently for larvae and for evidence of damage.

  For information on techniques to monitor levels of larvae of bertha armyworm, and economic thresholds, see: