See birds in the field? Scout for cutworm

CCC senior agronomy specialist Jim Bessel says that if you see ravens or seagulls or other birds congregating in your fields, get out and scout for cutworms. Wet weather often forces cutworms to the surface, where birds will eat them.

Note that cutworms can cause crop damage from the surface, feeding on above-ground parts of canola plants.

Even if you don’t see birds, cutworm scouting is a good idea. Look first in high spots, sandier soils and south facing slopes. Wilted, cut or missing plants are signs of cutworm feeding.

A number of cutworm hotspots have flared up, with reports of spraying or reseeding from many areas of Alberta, around Carrot River, north of Melfort, Cudworth and Lanigan in Saskatchewan, and from Swan River and Minto in Manitoba.

When scouting, cut open cutworms and look for “green guck” inside. That means they’re feeding — and still doing damage. If no green guck, then cutworms may have grown past the feeding stage or are between molting stages and there’s no sense spraying at this time.

Fields will be at higher risk of cutworm damage if the previous crop was canola, peas or forage, or if this year’s crop was seeded early.

Control: There is no established economic control threshold for cutworms in canola, but a MAFRI factsheet suggests 25% to 30% stand reduction as a time to act. In thin stands, the threshold may be lower. Apply insecticide in the evening for better results. The MAFRI factsheet says sometimes it is most economical to just treat infested patches and not entire fields.