gray field slug

not listed

NNA - Not applicable

not listed

Gray field slug, also known as milky slug, is a common, exotic, terrestrial, smooth land slug.

It is native to northern Europe, North Africa, and the Atlantic islands. It was introduced into North America and now occurs across the continent. It is most common in southern Canada and northern United States. It can be a serious crop pest, but is not listed as invasive nationally or in Minnesota. It is usually found above ground but under stones or leaf litter in open areas, especially cultivated areas.

The adult is stout, 1⅜″ to 2″ long and slender when stretched out, short and bell-shaped when contracted. It has no visible external shell. The skin is thick and is covered with raised areas (tubercles) and grooves, giving it a granular appearance. The tubercles may be white, cream, gray, or tan. The grooves are more or less covered with darker brown or gray flecks. The saddle-shaped covering on the front of the body (mantle) is short but usually covers more than one third of the body. The breathing pore (pneumostome) is on the right hand side of the rear quarter of the mantle. It is difficult or impossible to see if not open. When open, it has a raised, pale border. Concentric wrinkles on the mantle form a fingerprint-like pattern. The pattern is off-center, centered on the pneumostome. There is a short, longitudinal ridge (keel) at the end of the tail. The underside of the foot (sole) has three distinct longitudinal regions. The central region is gray, the lateral regions are whitish to grayish-yellow. The mucus is clear but can become white when the slug is disturbed.

Total length: 1⅜″ to 2″

This is the only Deroceras species that can change its mucus from clear to white.

Marsh slug (Deroceras laeve) is smaller, no more than 1⅜″ in length, and darker, smoky bluish-black.

Some other Deroceras species are identical in appearance and can only be distinguished when dissected by the male genitalia. However, they do not occur in Minnesota.

Agricultural fields, parks, gardens, roadsides, and other open, cultivated areas

Probably two generations per year

Gray field slug is active at night. During the day it remains concealed in the ground. It does not burrow but uses existing crevices and worm holes. At night, it climbs onto vegetation to feed.

When at rest, the body is contracted and the tentacles are retracted. When disturbed, it exudes white mucus over its entire body, leading to one of its common names, milky slug.

Eggs and/or hatchlings overwinter in soil. Adults die in the fall.

Sources disagree about the life cycle of gray field slug. Some sources say that adults overwinter. Others say the mostly eggs, sometimes juveniles, overwinter. Still others that hatchlings overwinter and adults die in the fall.

Fresh leaves, fruits, and seedlings

Sources

24, 29, 30.

Native to Europe and North Africa. Introduced.

Common

Location: Zimmerman, MN

Location: 5027 Tiger Lily Lane, Makinen Minnesota 55763

Location: Woodbury, Minnesota

Location: Woodbury, Minnesota

Location: Woodbury, Minnesota