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Slugs

Quick facts 

  • Slugs are slimy, soft-bodied animals, described as shell-less snails.
  • They are present from spring to fall, in cool, moist areas with shade. 
  • Slug population increases during rainy season and on well-irrigated gardens.
  • Slugs feed on leaves of many plants (especially seedlings), ripening fruits and vegetables, and decaying plant matter.
  • They feed at night and hide during the day.
  • Slugs create irregular holes on leaves and fruit and affect the appearance of the plant.
  • Extensive feeding can result in a weak or dying plant.
  • Baits and pesticides can be used to control slugs, along with with other methods like setting traps and barriers.
A slimy brownish slug on a green leaf
A typical slug

How to identify slugs

Slugs can be described as snails without shells. They are related to clams and oysters.

  • Slugs are slimy and soft bodied, without any legs.
  • They are generally brownish or grayish.
  • Their head contains two pairs of feelers — a larger pair above carries the eyes and a lower pair below is used for smelling.
  • They can range in size from 1/4 inch to two inches or longer.

The presence of slugs in your garden can be checked by looking for signs of slug movement or slug feeding. They may be seen at night or during the day in cool, shaded sites.

Slugs produce slime and use the slime to move. If you see a dried slime trail, it could mean that slugs are active in your garden.

Life cycle of slugs

In Minnesota, slug eggs can live through the winter.

  • In the fall, slugs lay their translucent eggs under plant debris, mulch, boards or in the soil.
  • Eggs hatch the following spring and slugs start feeding on strawberries in spring and early summer.
  • Slugs have a layer of slime to protect their skin from drying up.
  • When they move, they leave a slime trail which can be used to identify their presence.
  • Slugs have a structure called the radula, which contains small teeth and damages fruit. The radula scrapes or cuts food before eating it. 

Damage caused by slugs

Slugs use file-like mouthparts to rasp and chew plant tissue. Because of their mouthparts, they create irregularly shaped holes in leaves and fruit.

  • In cases of severe damage, complete defoliation of young plants could occur.
  • Slugs can create holes of varying size in fruit.
  • The damage can be unnoticeable scraping on the surface of the fruit to significant cavities equal to half of the fruit.
  • When present in large numbers significant damage can be done to fruit.
Slug on a hosta leaf with irregular holes
Slug feeding on hosta
Brownish slug making holes on a tomato
Slug damaging tomato
Hole created on a strawberry due to slug feeding
Slug damage on strawberry

How to protect your garden from slugs

If slugs are a problem in your home garden, it is best to use a variety of steps to reduce their numbers.

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Jeffrey Hahn, Extension entomologist

Reviewed in 2018

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