2010 Bertha Armyworm Forecast

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Bertha armyworm (Mamestra configurata) is being monitored in 2010 using a network of 114 pheromone-baited traps placed throughout the prairie provinces. Pheromone traps are used to determine the density and distribution of moths.

For the 2010 bertha armyworm survey results follow this link to the Agriculture Canada tri-provincial forecast maps. Please go to the drop-down menu to locate the bertha armyworm map.

Bertha armyworm populations are normally kept in check by such factors as weather and natural enemies. Generally parasitism rates of 50 - 60% in Bertha larval populations have indicated the end of a local outbreak. Cumulative moth counts in traps during June and July of 2010 help determine the level of risk for August. The results from 2009 suggest that bertha armyworm is a low part of the cycle.
The damage potential of bertha armyworm larvae is dependent on the plant's growth stage, the stage of the larvae, the number of larvae present weather conditions. An insecticide application is recommended when the larval numbers meet the economic threshold (high enough that the value of the crop they consume is greater than the cost of controlling them). The bertha armyworm pest forecasting program for the Alberta, conducted since 1995, has been funded by Alberta Agriculture and Food. Provincial government personnel, industry agronomists, Applied Research Associations, Agricultural Fieldmen and cooperating growers maintain the pheromone trap network. The cumulative moth count maps are prepared by Alberta Agriculture and Rural Development.

Potential damage from bertha armyworm may be more or less severe than suggested by the moth count data depending on weather and crop conditions. The objective of the monitoring is to heighten the awareness of canola producers to the damage potential of bertha armyworm and not to replace field scouting.

Cumulative moth catch Risk LevelInterpretation
0 to 300LowInfestations are unlikely to be widespread, but fields should be inspected for signs of insects or damage.
300 to 900UncertainInfestations may not be widespread, but fields that were particularly attractive to egg-laying females could be infested. Check your fields.
900 to 1200ModerateInfestations likely, canola fields should be sampled regularly for larvae and for evidence of damage.
1200+High Infestations very likely, canola fields should be sampled frequently for larvae and for evidence of damage.

Economic thresholds for bertha armyworm
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For more information about the content of this document, contact Scott Meers.
This document is maintained by Shelley Barkley.
This information published to the web on May 5, 2010.
Last Reviewed/Revised on June 30, 2010.