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Ministry of Agriculture, Food and Rural Affairs

Cutworms

Cutworm Cutworm on Chickweed
Click to enlarge.

Beginner

Scientific Names
Euxoa messoria
(dark-sided), Euxoa scandens (white cutworm), Agrotis ipsilon (black), Euxoa detersa (sandhill cutworm)

Identification

  • Dark-Sided, White, Black and Sandhill Cutworms are common species found in Ontario.
  • Larvae are soft and fat and up to 1.5" (4 cm) in length. They roll up into a tight circle when disturbed.
  • Cutworms are usually found in the top 1" (2.5 cm) of soil at the base of the spears.

Often Confused With
Hooking
Sand Blasting

Period of Activity
Depending on the species, cutworms may have up to 4 generations per year. Feeding activity during harvest is typically the most damaging to asparagus.

Scouting Notes
If damaged spears appear in the grading line, take note of which field(s) they came from and scout accordingly. In the field, carefully inspect a minimum of 10 groups of 10 plants across the field. While scouting, look for hooked spears or spears with scar tissue running down the length of the plant.

Thresholds
Control if more than 5% of the spears have been damaged, based on assessments from either the field or the grading line.

Advanced

Scientific Names
Euxoa messoria
(dark-sided), Euxoa scandens (white cutworm), Agrotis ipsilon (black), Euxoa detersa (sandhill cutworm)

Identification
Dark-Sided, White, Black and Sandhill Cutworms are a commonly found species in Ontario. They are all general feeders and attack many agricultural crops.

The larvae are soft and fat, and they roll up when disturbed. Look for cutworm larvae in the top 2.5 cm of soil surrounding the damaged plant. Depending on the species, the colour ranges from dark grey, to brown to light tan. They grow up to 4 cm in length.

Early-season cutworms attack the emerging spears, usually cutting them below or at the soil surface. Damaged spears may form a long scar, or emerge from the soil malformed or hooked. This damage is similar to sand blasting and frost. Sand damaged spears typically hook into the direction of the prevailing winds, while cutworm damaged spears point in all different directions. Phytophthora also causes hooking, however it is usually associated with wet spots and low-lying areas.

Often Confused With
Hooking
Sand Blasting

Biology
Cutworms overwinter as eggs, larvae, pupae or adult moths depending upon the species. Not all cutworm species overwinter in Ontario. The adults arrive in Ontario throughout April and May.

The female moths are attracted to lush, green vegetation and lay their eggs immediately. Chickweed and other fall-germinating annual or perennial weeds are common cutworm habitat in early spring.

Egg hatch and early-feeding often coincides with the asparagus harvest season (early-May through mid-June). Larvae feed for up to 4 weeks. Once the larvae reach 2.5- 4 cm (1- 2 in.) in length, they cease feeding as they prepare to pupate. There are several generations per year; however the first generation is most likely to cause economic damage in asparagus.

Most species of cutworms feed at night, hiding during the day under loose stones or in the soil near the base of the plant.

Period of Activity
Depending on the species, cutworms may have up to 4 generations per year. Feeding activity during harvest is typically the most damaging to asparagus.

Scouting Notes
If damaged spears appear in the grading line, take note of which field(s) they came from and scout accordingly. In the field, carefully inspect a minimum of 10 groups of 10 plants across the field. While scouting, look for hooked spears or spears with scar tissue running down the length of the plant.

Thresholds
Control if more than 5% of the spears have been damaged, based on assessments from either the field or the grading line.

Management Notes

  • Control winter annual and perennial weeds in the fall or early-spring to eliminate egg-laying habitat.
  • If cutworms become a problem in rye cover crops, consider replacing the rye with a cover crop that is killed over winter, such as oats or oilseed radish.
  • Cutworm control is most effective on small (less than 2.5 cm or 1 in.) larvae. Larger larvae are difficult to control with insecticides. At more mature stages (> 2.5 cm or 1 in. in length), they cease feeding as they prepare to pupate, and control becomes unnecessary.
  • Apply insecticides in the early evening, as the cutworms come to the surface to feed at night.
  • Insecticides are more effective on moist soils.