Higher cabbage seedpod weevil populations prompt early field scouting
Alberta Canola is advising canola growers in Central Alberta to monitor fields closely for cabbage seedpod weevils (CSPW) as populations continue to expand across the region.
Recent observations have shown that the pest is becoming more common in areas where it has not traditionally been a concern. Growers are now finding cabbage seedpod weevils farther north than in previous years, increasing the need for early field scouting and monitoring.
The first step is to inspect flixweed patches, volunteer canola, and other canola-related weeds. These locations can provide early signs of weevil activity before populations move into canola fields. Since the insects are strongly attracted to yellow flowers, they are often found in the earliest flowering areas along field edges.
While these spots help identify the presence of weevils, management decisions should be based on field-wide sampling rather than observations from a single location.
Farmers should begin sweep-net sampling from the early bud stage through the 10 to 20 percent flowering stage. Early seeded crops may attract migrating adult weevils first, making regular scouting especially important. A practical approach is to take sweep samples from several areas of the field and calculate an overall average.
The economic threshold is generally reached when field averages fall between 25 and 40 weevils per 10 sweeps.
Understanding the pest’s life cycle is also important. Female cabbage seedpod weevils lay eggs inside developing canola pods. After hatching, each larva can feed several seeds before completing development, reducing yield potential.
Timing is critical when applying insecticides. Spraying too early may not provide effective control because pods may not yet be large enough for egg laying. In addition, adult weevils may still be moving into fields during early flowering. Treating crops before most weevils have arrived can reduce control effectiveness and may require additional management later in the season.
Careful scouting and well-timed decisions remain the best tools for protecting canola yields from cabbage seedpod weevil damage.
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