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Manitoba Agriculture, Food and Rural Initiatives
Interpreting Bertha Armyworm Cumulative Moth Counts
The population of adult bertha armyworms are monitored during the flight and egg-laying period. Monitoring is done using pheromone baited traps. The monitoring period extends from about early-June through July. Each week moths caught in the traps are counted, and data for that week, as well as cumulative moth counts, are entered into the table for the appropriate agricultural region. The cumulative total number of moths will continue to rise until the end of the monitoring period. The following table relates the cumulative moth counts with the risk of larval infestation.
Cumulative Number of Moths/Trap |
Larval Infestation Risk Level |
From |
To |
|
0 |
300 |
Low - Infestations are unlikely to be widespread, but fields should be inspected for signs of insects or damage. |
300 |
900 |
Uncertain - Infestations may not be widespread, but fields that were particularly attractive to egg-laying females could be infested. Check your fields. |
900 |
1200 |
Moderate - Canola fields should be sampled regularly for larvae and for evidence of damage. |
1200 |
1500+ |
High - Canola fields should be sampled frequently for larvae and for evidence of damage. |
For further information, contact your GO representative.
