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28 Mar 2024

Best organic slug and snail controls

We test the most effective ways to stop these pests munching on your plants

Adele DyerPrincipal researcher & writer

In this article

The best organic slug and snail controls from our test
How to get the best from slug controls
Does slime protect slugs and snails?
Which slug controls work?
How we tested slug and snail controls

Slugs and snails are very discerning in what they eat, bypassing the weeds to devour our favourite plants.

They're difficult to stop and, while you can still use bated pellets containing ferric phosphate, biological control containing nematodes or just pick off any slugs or snails you see, different types of physical barriers are an increasingly popular choice.

The Which? Gardening experts looked at the current options to find out which are the most effective.

The damp winter and spring weather in 2024 is providing just the conditions that slugs and snails enjoy so be ready to protect your plants.

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The best organic slug and snail controls from our test

Only logged-in Which? members can view the full test results. Join Which? now to get instant access to our test scores and Best Buy recommendations below.

Slug and snail controls	Overall score	Type of barrier control	Ease of use	Time taken before first damage seen	Time taken for >10% of leaves to be eaten	Percentage of leaves damaged at the end of the trial	Number of plants damaged	Durability of treatment
Doff Slugs Be Gone Defence Gel
Ecofective Slug Defence Plant Spray
Ecofective Slug Defence Barrier Granules
Evergreen Slug Clear Slug & Snail Barrier
Grazers G2 Slugs & Snails
PlantGrow Slug & Snail natural barrier
SlugLess Pet Safe, Spiky Slug & Snail Deterent

Best Buys need to score more than 75%.
SCORE: Ignores price and is based on: time before first damage seen 20%; time taken for >10% of leaves to be eaten; percentage of leaves eaten at the end of the trial 20%; number of plants damaged at the end of the trial 20%; ease of application 10%; durability of treatment 10%. All scores are based on comparisons between treated and untreated plants in the same three plots. Scores for the untreated plot used as a control are given separately.

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How to get the best from slug controls

Put barrier products in place as soon as you sow seeds, plant new plants or spring growth appears on existing plants.
Carefully follow label advice on barrier depth, width and distance from plants, or spraying instructions.
Check and reapply barriers and sprays as needed after heavy rain and check frequently during prolonged periods of wet weather.
As plants grow, any leaves that extend over the barrier might be eaten. A second, wider barrier row should help until the plants are large enough to fend for themselves.
Combine a barrier product with baited pellets and/or hand removal of slugs and snails for greater protection, especially in spring when plants are small and during mild, wet weather.

Get more advice on getting rid of slugs and snails

Does slime protect slugs and snails?

With the slime trails they produce, molluscs are well adapted to travelling over the most inhospitable surfaces to get to feed, which is why things like eggshells rarely work. So we're glad to find some barrier controls that reduced the amount of damage as successfully as the baited pellets. The crucial factor seems to be finding something molluscs dislike enough that they'll feed on unprotected plants instead of crossing it.

It's quite likely that you'll still see some damage to your vulnerable plants, especially when wet weather brings a lot of hungry molluscs out of the prowl.

But if you can deter slugs and snails long enough to let plants establish and grow, your plants have a much better chance of survival.

Which slug controls work?

We've tested slug and snail controls regularly over the years and found that many common suggestions are very ineffective.

Copper tape can help when applied to pots, but we've seen snails crawl across it within a day.
Crushed eggshells and coffee grounds aren't much of a deterrent and are easily broken down by wind and rain.
Few slugs are killed in beer trapes - and ground beetles and centipedes are often the unintended victims.
Ferric phosphate pellets have proved an effective solution in previous trials as well as this one and, for slugs, watering a solution of nematodes (Phasmarhabditis hermaphrodita) onto the soil is equally effective, although they don't work on snails.

How we tested slug and snail controls

The trial was carried out in a well-ventilated polytunnel in soil free from slugs and snails. Three 1m² plots, each surrounded by slug and snail-proof fence, were used for each product.

The plots were planted with six young lettuce plants and six young sunflower plants.

The products were applied to three lettuce and three sunflower plants in each plot, while the other six plants were left untreated. A further three plots were set up with had no treatments.

All treatments were reapplied as needed during the trial, following product instructions.

We placed 10 slugs and five snails in each plot. Plots were watered heavily near the start of the trial to see what effect heavy rain has on the products and were watered regularly after that to keep soil moist.

The trial ran for three weeks. We assessed how easy it was to use the products, how well they lasted, and we regularly recorded leaf damage and the number of plants damaged on each plot.