What Growers Should Know and Do Now
As canola crops continue to mature unevenly across Alberta, growers should keep an eye out for one last insect pest before harvest in 2026 and again next year.
Bertha armyworm populations are increasing in some regions of the province in 2026 after several years of relatively low activity. Reports of economic populations and insecticide applications have come from areas earlier in August including Vulcan County, Drumheller and parts of the South Peace region.
The best way to assess risk is through field scouting. While earlier adult moth trap counts can help identify areas with higher potential pressure, Bertha armyworm populations can vary significantly from field to field. Scouting remains the only way to determine whether control is required.
Early feeding is often first noticed on leaves within the crop canopy. As larvae grow, and consume existing leaves, they move onto pods and can cause significant yield loss if populations exceed economic thresholds. Detecting infestations early gives growers time to assess populations and make management decisions before serious pod feeding occurs.
A general rule of thumb in the past has been that approximately 20 larvae per square metre may justify an insecticide application, but growers should use current economic threshold guidelines when making decisions.
Natural enemies can also play an important role in reducing Bertha armyworm populations. Beneficial insects, parasites and diseases can help suppress outbreaks, although healthy larvae may continue feeding on maturing pods right up to harvest.
Before applying an insecticide, be sure to check pre harvest intervals and consider your harvest plans. Bertha armyworms can continue feeding even under swathed canola, making timely control decisions important where populations warrant control.
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