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Risk Forecast for Bertha Armyworm in Manitoba in 2015


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.

The cumulative counts from the traps, which is presented in the map and table below, can not predict what levels of larvae will be, but can be used to determine areas of the province where increased monitoring of fields may be necessary. Seventy-eight traps were monitored for bertha armyworm in 2015.

Cumulative trap counts (as of July 22, 2015) are all still at low risk of larvae of bertha armyworms being at economic levels in Manitoba. No trap counts have gone into the uncertain risk category. 
While scouting canola fields, it is still advised to check the ground for larvae and assess plants for signs of potential feeding by bertha armyworm.
Highest cumulative trap counts over the trapping period, as of July 22, 2015, are:
Location GO Team Cumulative Count
Darlingford Pembina 264
Alexander Southwest 192
Douglas Southwest 177
Inglis South Parkland 170
Somerset Pembina 165
Tourond Eastman 105
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.


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