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Chicago Urban Gardening

The day to day experiences of a University of Illinois Extension Urban Horticulture Educator in Chicago, Illinois


Posted by Ron Wolford -

Slugs belong to a group of animals known as mollusks and resemble leaches. Although somewhat selective, slugs feed on a wide variety of living plants and feed extensively on certain fungi and decaying plant matter. Slugs slide along by means of a long, flat, muscular organ known as a foot. Mucus, or "slime," aids in the locomotion and later dries to form a shiny white or silvery "slime trail," which is a clue to the presence of slugs in the garden.

Slugs are active at night or on dark, cloudy days. They may be found during the day under leaves and litter, beneath low growing plants or burrowed a short distance beneath the soil surface. It is interesting to note that cultural practices in the garden that retain soil moisture and prevent soil temperature extremes may promote better plant growth, but they also induce larger slug populations. Thus, control may be difficult, but it is possible, if the following measures are taken.

Effective control begins with proper sanitation. Check new plants carefully before planting. Examine the soil, breaking apart the roots and looking for slugs. Remove weeds and unnecessary foliage, boards, stones and other debris so that the soil surface dries out more rapidly.

Slugs seeking cover during the day can be trapped under boards or flowerpots placed throughout the garden and yard. Boards 12 inches wide and 15 to 20 inches long, raised up off the ground by one-inch runners, make excellent traps. Remember to gather them each day when using traps.

Beer bait traps may attract slugs. Place saucers or pans of beer in depressions in the ground at intervals of 10 feet. Yeast may be added to the beer to increase its attractiveness. The pan edges should be at ground level so these pests can climb in and be trapped. Remove and dispose of them each morning. Beer traps may not be as effective as many gardeners are led to believe. Many slugs will remain in the garden. Additionally, slug traps may attract some beneficial insects.

Slugs will not crawl over an irritating substance if it can be avoided. A number of materials including ammonium sulfate, lime, ashes, crushed eggshells or sand have been used effectively as barriers. An inch-wide band of one of these can be used around individual plants, around vegetable gardens or even along fence lines to keep slugs from moving in. The effectiveness of these barriers is decreased when they become wet. An inch-wide band of copper–from copper flashing, to tubing, to rows of pennies–will also deter slugs. The chemical reaction between the copper and the slug's slime keeps the slug from crossing into the area.

Poultry, especially geese and ducks are probably the most effective predators of slugs in the home yard and garden. However, damage to seedlings and young plants by the birds would be unacceptable. Some toads and snakes are slug predators.

The one thing that is not recommended is salt. While salt can kill a slug, it can also poison the soil so plants don't grow. After good sanitation techniques have been initiated, chemical baits can be effective in reducing slug population. Contact your local Extension office for the current recommendations.

Source: David J. Robson, Extension Educator, Horticulture,

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