By Judy Sedbrook,Colorado Master GardenerSM, Colorado State University Cooperative Extension, Denver County
Garden slugs are 1-1/2 to 2 inches long when full-grown and are gray to black in color. They are not insects but mollusks, like oysters and clams, and are often described as snails without shells. Slugs move along by secreting a path of mucus.
Hatching from masses found in damp areas of the garden, slugs are one of the first pests of spring. They begin hatching when temperatures are consistently greater than 40 degrees F. Young slugs resemble the adults and begin feeding as soon as they have hatched, creating large holes in the leaves, fruit and crowns of plants.
They prefer damp, cool locations and will hide in soil crevices, earthworm holes or under leaves, boards or other garden debris during the day. Wet weather in spring and early summer results in an increase in the slug population. If the weather is dry, they will die or burrow deep into the soil until conditions improve.
Slugs feed at night, leaving a silvery trail behind them as they move; a sure sign of their presence. They can consume several times their own body weight each night, causing serious damage in a short time.
For more information on slugs, see CSU Fact Sheet 5.515.
Photograph courtesy of Judy Sedbrook.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010