Regional Gardening Reports :: National Gardening Association

In the Garden:
Rocky Mountains
August, 2004
Regional Report

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Slug damage on newly emerging amaryllis leaves is rarely this decorative.


They make sneak attacks at night and chew leaves and succulent stems of plants. Large populations can infest lawns. Signs of their invasion can be found in the morning as shiny, dry, slime trails leaving the area.

You've just encountered some very common pests throughout the Rocky Mountain region -- slugs. They are not insects but mollusks, related to shellfish, such as clams. Slugs can cause significant damage in vegetable, fruit, and flower gardens, where their feeding causes a rasping or scraping of plant tissues.

Slugs creep along a cushion of mucous or a slime trail during their raids. They primarily come out at dusk and feed during the night, avoiding the hot, drying conditions of daytime. Slugs can also be active during rainy or cloudy days.

Natural Enemies
If you live on a farm or ranch, you can count on peacocks, ducks, and geese roaming the landscape to devour these slimy delicacies. Toads and snakes will also feed on slugs. The larvae of some fireflies and parasitic flies will seek out and attack and parasitize young slugs.

Physical Controls
Conscientious hand-picking is an important control and can be combined with other tactics. If you're squeamish about picking up slugs, wear plastic gloves or use tweezers to capture them. Put them in a container of half and half vinegar and water to finish them off. Trapping slugs in shady areas of the garden can be effective. Use overturned clay pots to lure slugs to these protected retreats during the early morning hours. Leave the soil beneath the pots uneven so the slugs will crawl underneath the rim. Inverted grapefruit and orange halves (after you've eaten the contents) are excellent lures. Just pick up the collection of slugs the following day.

Slugs are attracted to fermenting liquids so beer traps can be utilized to capture a good share of them, that is if you're willing to share the brew. Bury shallow containers, such as empty tuna or cat food cans, with rims level to the ground, and fill them with the beer or a mixture of 1 teaspoon sugar, 1/4 teaspoon yeast dissolved in a cup of water. Check traps each morning and destroy any slugs.

Barriers against slugs are becoming more popular. Slugs will avoid crossing copper barriers since the metal is toxic to them. Place copper strips (such as Snail-Barr) at least 2-1/2 inches wide around vulnerable garden areas. To be effective, make sure that no leaves or stems bridge the copper strips or the slugs can cross over and invade the protected areas.

Diatomaceous earth and hardwood and softwood ashes are good barriers if kept dry. Dry sawdust from local woodworking shops is another good barrier. There is a drawback when using these materials, however, since they become less effective when wet from rain or irrigation.

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