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Ministry of Agriculture, Food and Rural Affairs

Slugs

Slug Slug feeding damage Slug Slug with eggs Click to enlarge.

Beginner

Scientific Names
Arion, Deroceras, Helix and Limax species

Identification

  • Soft-bodied, legless, grey mollusks.
  • Feed above or below ground, depending on the soil moisture level.
  • Have rasping mouth-parts.
  • Will create ragged holes on the lower leaves, sometimes leaving a “window-pane” of waxy cuticle behind.
  • Severely affected plants may become skeletonized.
  • Under high populations, slugs also attack seeds and emerging seedlings.
  • A slime trail is usually observed at the feeding location.

Often Confused With
Hail injury
Corn flea beetle

Period of Activity
Slug damage is most severe in years when there is prolonged cool, wet weather during May and June. Slugs are active at night or on cloudy, high-humidity days. They feed every second day.

Scouting Notes
Begin scouting fields at the spike to 4-leaf stage. Inspect at least 10 groups of 10 plants across the field. Take note of any plants with un-even, narrow “window panes” running lengthwise down the leaf. Also look for skeletonized leaves or defoliated plants.

Thresholds
None established. After the 6-8 leaf stage, slug feeding is less likely to cause economic damage to the crop.

Advanced

Scientific Name
Arion, Deroceras, Helix and Limax species

Identification
These soft-bodied, legless, grey mollusks feed above or below ground, depending on the soil moisture level. Slugs have rasping mouth-parts and will create ragged holes on the lower leaves, sometimes leaving a “window-pane” of waxy cuticle behind.

Severely affected plants may become skeletonized. Under high populations, slugs also attack seeds and emerging seedlings. A slime trail is usually observed at the feeding location.

Often Confused With
Hail injury
Corn flea beetle

Biology
Slugs mate in late summer and overwinter as eggs. The eggs hatch in early spring. Slugs are generalist feeders and may cause damage on a wide variety of vegetable crops. Slugs enter a dormant state under hot, dry conditions.

Period of Activity
Slug damage is most severe in years when there is prolonged cool, wet weather during May and June. Slugs are active at night or on cloudy, high-humidity days. They feed every second day.

Scouting Notes
Begin scouting fields at the spike to 4-leaf stage. Inspect at least 10 groups of 10 plants across the field. Take note of any plants with uneven, narrow “window panes” running lengthwise down the leaf. Also look for skeletonized leaves or defoliated plants.

Thresholds
None established. After the 6-8 leaf stage, slug feeding is less likely to cause economic damage to the crop.

Management Notes

  • Most plants can successfully outgrow light feeding damage.
  • Cultivating fields where slug pressure is high can help reduce the slug population. Tillage exposes the slugs to dehydration and predation by birds and mammals.
  • Removing weeds and crop residue from the zone immediately surrounding young seedlings may also help reduce damage.
  • Zone tillage can remove slug habitat while maintaining the benefits of reduced tillage.