Controlling Slugs and Snails

by Sue McDavid

UCCE Master Gardeners of El Dorado County

This article originally appeared in the July 19, 2023 Mountain Democrat

If you garden, you will eventually need to deal with slugs and/or snails, which leave the tell-tale mucus or slime trails as they move. This material helps them glide forward and stick to surfaces. The most important difference between the two is that snails have visible, external shells while slug shells are small and lay underneath their skin.

Snails and slugs leave irregularly shaped holes in plant foliage, and are most active at night and on cool, overcast days. Young seedlings and succulent herbaceous plants are particular favorites, but they also eat decaying plant material. The damage slugs and snails do can sometimes be confused with chewing insects such as earwigs; go out at night with a flashlight to identify them.

Since snails and slugs prefer to hide during daylight hours, getting rid of their hiding places around the garden is a good way to start controlling them. Boards, rocks, dense ground covers, and the like, are some favorite hiding spots, so clearing these is a successful control method. Another good control method is to switch from overhead irrigation to drip irrigation, which greatly decreases humidity and moist conditions that are favored by slugs and snails. Handpicking is another way to eliminate these mollusks; for the squeamish, wearing gloves will remove the need to touch them directly. Traps can also help. Bury small cans such as tuna cans to soil level and fill with beer or sugar water with yeast; the critters will fall into the mixture and drown after which they can be disposed of.

Baits can also help, but it is not recommended that any containing metaldehyde be used. Metaldehyde is very toxic to cats and dogs if ingested. Instead, use baits containing iron phosphate which causes snails and slugs to stop eating; they will die in 3-6 days. Iron phosphate baits will need to be reapplied every 2-3 weeks.

To minimize damage, you can select plants that are unattractive to snails and slugs such as highly scented plants. For example, lavender, rosemary, sage, nasturtium and lantana are less attractive to snails and slugs than plants with succulent foliage such as beans, cabbage, lettuce, dahlias, delphiniums, hosta, strawberries, and many vegetables.

You probably will not be able to eliminate these creatures entirely from a garden, but using a combination of control methods will greatly reduce the population. Diligent monitoring is perhaps the best way to keep them at a minimum. A good resource for information can be found at        https://ipm.ucanr.edu/PMG/PESTNOTES/pn7427.html  

Master Gardener classes are offered monthly throughout the county. You can find our class schedule at: http://mgeldorado.ucanr.edu/Public_Education_Classes/?calendar=yes&g=56698, and recorded classes on many gardening topics here: http://mgeldorado.ucanr.edu/Public_Education/Classes/

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