Released on August 8, 2006
An outbreak of Bertha armyworms is causing problems for some Saskatchewan canola producers, primarily those in the eastern and northern parts of the province. While infestation levels vary widely from one field to the next, insecticide application is warranted.The egg stage of the Bertha armyworm lasts about five to seven days, and the average life span of the larvae is about six weeks, depending on temperature. Warmer conditions may accelerate the insect's development. The Bertha armyworm will move to other fields when food supplies become scarce or when crops ripen. Producers should monitor their fields regularly in the evenings, when the larvae are feeding, to determine whether action is required.
Economic thresholds have been established based on the cost of insecticide and application and the expected value of canola. The threshold ranges from 10 to 34 larvae per square metre, depending on crop value and cost of control.
If control measures are required, registered insecticides can be applied by air or ground. Producers should ensure timely insecticide application, with adequate water volumes. Best times for application are evening and early morning, since larvae are usually actively feeding during these times.
Additional information about the Bertha armyworm, including the economic threshold table, is on Saskatchewan Agriculture and Food's website at www.agr.gov.sk.ca
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