Controlling Snails and Slugs in the Garden
By Michelle Le Strange
7:34 am,
June 6, 2024

Snails and slugs are closely related. They both have soft, oblong bodies and produce slime to help them move around. The most obvious difference is that snails have shells. Both are active mostly at night and on dark, cloudy days. On sunny days they can be found in moist, shady spots. 

Reducing populations of slugs and snails in the landscape requires persistence. Look for their eggs in the soil about an inch down or under rocks, boards, or plant debris. Eggs resemble small pearls and are laid in masses (sometimes 100). When you find eggs, crush them. Try combining several methods to reduce their numbers and don’t rely solely on pesticide baits. 

Hand pick at night 

To be effective, handpicking must be done thoroughly and regularly. Collect nightly until it’s hard to find snails and slugs, and then check once a week. Crush them completely (otherwise they may recover and walk away) or drown them in a pail of soapy water (they’ll survive in plain water). 

I usually go snail hunting in the garden with a used plastic container in hand. After I’ve made my rounds, I put the top on the container and throw it in the garbage can. If just picking a few snails I pitch them into the street for cars to crush or I throw them at my wood fence.

A few dead snail/slug bodies left on the soil surface will attract others and make snail collecting easier, but large piles will breed flies. Instead bury the crushed mollusks 3 or 4 inches underground. This adds nutrients to the soil and avoids fly problems altogether. 

Use barriers

Before placing barriers, hand-pick for a couple of nights. After placing barriers, check for snails and slugs caught inside the barrier. 

  • Wrap a strip of copper barrier tape around a tree trunk, flower pot, or the wooden sides of garden beds or fences. Snails and slugs are repelled by the unpleasant reaction between their bodies and the copper. 
  • Cover seedlings with small cages made from plastic or galvanized metal window screen. Push the cages into the soil so snails and slugs can’t squeeze under. 
  • Cover rows of vegetables with special horticultural fabric that lets in light and water but excludes snails and slugs. 
  • Around plants apply a ring of coconut oil soap to repel slugs and snails.
  • Barriers of diatomaceous earth, lime, sawdust, ashes, etc. are not as effective, especially when wet and maybe be detrimental to your soil. 
Snail traps

Snails and slugs can be trapped under upside-down flower pots, dark colored plastic sheeting, and wooden boards. Place these traps around the garden and collect snails and slugs in early morning. Homemade or commercial pit traps that use beer or yeast mixtures to lure snails and slugs to a drowning death may help, but hand-picking will still be needed.

Allow natural predators

Many common ground beetles kill snails and slugs. Most are large (1 to 2 inches), black, tank like creatures. They are found in the same moist habitats as their prey, under rocks, boards, leaves, etc.

Use iron phosphate bait

Choose snail baits carefully. Some baits also kill earthworms and beneficial insects in the soil. Baits containing metaldehyde are highly toxic to children and pets, if ingested. Baits containing iron phosphate are safer and less toxic to humans, animals, and the environment, yet effective on snails and slugs. 

After eating iron phosphate, snails and slugs stop feeding and die within 3 to 6 days. They often crawl into secluded places, so you may not see dead bodies. Three applications at two week intervals are usually required of any bait product. 

Prevention

Snails and slugs find large expanses of ivy and other succulent ground covers particularly attractive, and they also hide in clumps of agapanthus, lilies, daffodils, and iris. They are less attracted to plants with dry hard leaves like rhododendrons, junipers, and heavenly bamboo. 

Moisture always makes an area much more attractive to snails and slugs.

Snails and slugs are actually great decomposers of dying plant material and can add organic matter to your soil. The problem is when they run out of dying plant material and turn to your ornamentals instead. Handpicking to keep the population under control and stop them from devastating your plants is your best bet.

This column is not a news article but the advice of the writer and does not reflect the views of Mid Valley Times newspaper.

About the Author

Michelle Le Strange