Slugs and Snails

Slugs and snails are among the most bothersome pests in many gardens in Missouri. Slugs and snails are mollusks, not insects, and are closely related to shellfish such as clams and crayfish. However, in the garden they can do as much or more damage than insects. Slugs and snails chew on the foliage of many plants, and young plants are often killed or suffer retarded growth by their damage. They cause the most serious damage to seedlings, or crops and fruits growing low to the ground. Fruits such as strawberries and edible parts of leaf and tuber crops can be completely destroyed by slug or snail feeding. Slugs and snails move by sliding along a mucous or slime trail. These slime trails then dry to form silvery pathways that provide an indication of their presence. Snails and slugs are the most active at night or during cloudy, damp days. They seek hiding in moist, dark places during sunny days to avoid the sun and heat and are attracted to well-mulched gardens.

The first step to managing snails and slugs is to eliminate daytime hiding places near your vegetable garden or flowerbeds. Boards, stones, debris, unused flower pots, weedy areas around tree trunks, dense ground covers in the shade, and leafy branches growing close to the ground are all ideal sheltering spots. Slugs and snails are highly sensitive to dry conditions as they have high water content and produce large amounts of protective mucous. As a result, practices that reduce humidity within the garden greatly limit populations of slugs and snails. Increasing air movement around plants reduces humidity, as well as using drip irrigation and soaker hoses. If overhead irrigation is used, apply early in the day to allow more time for leaves and soil surface to dry before slugs start their night foraging. There are many materials that are repellent to slugs and may make good barriers. Newly planted seedlings can be protected with 2 to 4 inch copper stripping placed vertically like a fence around the plant. Snails and slugs will not cross copper as their slime reacts with this metal to give them a small electric shock. Some materials such as wood ashes, crushed eggshells, and diatomaceous earth are highly abrasive and irritate the bodies of slugs and snails, thus making good barriers when spread around the base of a plant. The effectiveness of these barriers decreases with increased moisture and may need to be reapplied frequently, especially after rainfall. Salt is lethal to slugs and snails, however, applying salt to the garden aggravates existing soil salinity problems and is not recommended on a frequent basis. As an alternative, salt-impregnated strips are available on the market to repel slugs. Also, household ammonia is toxic to slugs and can be mixed with water diluted to about 10:1 and applied directly onto the slugs and snails. Do not spray when slugs or snails are on the plant as the ammonia can harm the plant.

Baits are perhaps one of the most interesting topics of discussion for controlling slugs and snails. Slugs and snails are attracted to chemicals produced by many fermenting materials, and these make excellent bait for traps. A shallow bowl or jar of beer or of sugar water and yeast effectively attracts, traps and drowns slugs and snails. These traps remain effective for several nights, but have a short distance of attraction and several must be placed throughout the garden. If there are plants that are more desirable near the traps such as hosta or leafy vegetables, the slugs or snails may select the desirable plants over the bait. Boards, moistened newspaper, unused flower pots, or old fruit rinds can be used to attract slugs and snails as they seek shelter, then checked in the morning and slugs and snails can be destroyed. Handpicking is a very effective tool for managing slugs and snails if done regularly. Handpicking should be done daily until a noticeable decline in numbers if observed. Crushing in a plastic bag is a very effective way to dispose of trapped slugs and snails. Slugs and snails do not prefer temperatures above 75 degrees F, so once summer arrives, populations should decline.

Mary Kroening
573-882-9633