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Index : Plant Problems - Cultural
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- 5. Snails and Slugs Can Be Desert Garden Problem - Top
- You may be surprised to learn that we do have snails and slugs in gardens here in Tucson area. Although we more often associate these slimy pests with wetter climates, moist and shady areas in desert gardens can also be vulnerable to damage from snails and slugs. Given our wetter than normal winter, we may be seeing even more of these slippery mollusks.
In the garden, snails and slugs feed on decaying organic matter and eat the leaves of most herbaceous plants. Any low-growing plant offers shade and a certain level of moisture that these mollusks need. Some of the plants most liked by snails and slugs include basil, beans, cabbage, marigolds, strawberries, and many vegetable plants.
Snails and slugs move by gliding along on a muscular “foot”. This muscle constantly secretes mucus, which later dries to form the silvery “slime trail” that signals the presence of either pest. In addition, leaves and flowers will be chewed, forming irregular holes with smooth edges. They also chew fruit and young plant bark. They can cause damage to strawberries, artichokes, and tomatoes that are close to or laying on the ground. Look for the silvery mucous trail to confirm the damage was caused by slugs or snails and not caterpillars or other chewing pests.
Snails and slugs will most often be found in improved garden and container soils. They lay their eggs in this loosened soil and hide under leaves, rocks, organic mulch, and other objects that provide protection from daytime heat and dry air. At night, when conditions are mild they come out to feed.
There are several ways to control slugs and snails. Hand picking them off of plants can be effective if done on a regular basis. As they feed at night, it’s necessary to go out and search over your plants with a flashlight. Water the area where feeding has occurred in the early evening to draw the pests out. For the squeamish, rubber gloves help in the picking. Place the snails and slugs in a plastic bag and dispose of them in the trash. Or they can simply be crushed and left in the garden. Household ammonia diluted to a 10% solution in water can also be spayed on collected slugs to kill them.
Trapping is also an effective means of locating and destroying these pests. Moistening the soil and laying down boards or setting out flower pots throughout a garden area will attract the snails and slugs to crawl under. Inverted melon rinds also make good traps. The much touted beer bait to trap and kill slugs and snails does work, but the beer must be changed daily to maintain it’s attractive properties. The beer should be poured in straight-sided cans sunk into the ground so that the rim is flush with the soil surface. Snails fall in and drowned, no doubt a painless death.
Snails and slugs have many natural enemies, including ground beetles, pathogens, snakes, and birds and they may provide some control. Keeping moisture levels down, especially on the soil surface in garden areas will also help, as will eliminating hiding places under objects.
Snail and slug baits are available but must be used with caution. Baits containing the active ingredient metaldehyde are most common. But metaldehyde baits are particularly poisonous to dogs and cats, and the pelleted form is especially attractive to dogs. Metaldehyde snail baits should not be used where children and pets cannot be kept away from them.
If leaves of plants appeared to be chewed but there are no signs of snails or slugs, then it’s likely a caterpillar is doing the damage. The most common caterpillars present at this time of year are tomato horn worms on tomatoes, orange dog caterpillar on citrus, and the Texas Mountain Laurel caterpillar. All can be controlled by hand picking or spraying with Bacillus thuringiensis, most commonly known as ‘BT’.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161. - Updated: April 10, 2005
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