There are five prominent cutworm species of concern in the canola growing areas of Western Canada.
The larval stage is the only damaging stage to canola.
1. Pale Western Cutworm
Identification: Mature larvae are pale grey to greenish grey in colour; head is yellowish-brown.
Distribution: Most commonly found in arid soils of Alberta and Saskatchewan.
Damage: Typically feeds on stems below the soil surface (subterranean feeder); surface feeds only when soil is very hard or wet. Damage appears as holes cut into new leaves.
Figure 1. Pale Western Cutworm. Source: Frank Peairs, Colorado State University. Bugwood.org
2. Redback Cutworm
Identification: Mature larvae have two dull red stripes along their back; head is yellowish-brown.
Distribution: Across the Canadian prairies.
Damage: Larvae feed on plants during the night and are inactive during the day; chew on leaves and stems at or above the soil surface (surface feeder).
Figure 2. Redback Cutworm. Source: John Gavloski, Manitoba Agriculture and Resource Development.
3. Army Cutworm
Identification: Larvae are pale green-gray to brown in color with black dots along a pale back stripe. The head is light brown with small dark spots.
Distribution: Arid regions of the prairies; rarely found in Manitoba.
Damage: Larvae feed on plants above ground in late afternoon/early evening (surface feeder).
Figure 3. Army Cutworm. Source: Frank Peairs, Colorado State University. Bugwood.org
4. Darksided Cutworm
Identification: Grayish and shiny in colour with a prominent white stripe along each side just above the legs; dark spots on the head.
Distribution: Canadian prairies; often found in combination with redback cutworms.
Damage: Larvae feed on emerging plants at or below the soil surface at night.
Figure 4. Darksided Cutworm. Source: John Gavloski, Manitoba Agriculture and Resource Development.
5. Dingy Cutworm
Identification: Grayish brown in colour with a thin light line down the very middle of the back; somewhat diagonal markings that look like tire tracks (“V’s”) on back; have four equal-sized black dots on the back surface of each abdominal segment.
Distribution: Canadian prairies.
Damage: Larvae climb and feed on leaves; stem feeding is rare.
Figure 5. Dingy Cutworm. Source: John Gavloski, Manitoba Agriculture and Resource Development.
Figure 6. Clipped canola plants due to cutworm feeding. Source: Canola Council of Canada.