pests diseases
Slugs and snails — UK + US control after metaldehyde ban
Beat slugs and snails with ferric phosphate baits, nematodes, copper tape, beer traps and night hand-picking. Full UK + US post-metaldehyde-ban guide.
Slugs and snails — UK + US control after metaldehyde ban
If you grow hostas, lettuces or dahlias in a damp climate, slugs and snails will find you. The Royal Horticultural Society has consistently ranked them at or near the top of its annual member pest survey, and a single keeled slug can eat several times its own body weight in tender foliage overnight. The job got harder in 2022 when the UK pulled metaldehyde, the active ingredient in most "blue pellet" baits, off the shelves for outdoor use. This guide is the modern, integrated control plan — UK and US — for getting slug and snail damage under control without resorting to a banned or pet-toxic product.
Try Growli: Snap a photo of the damage (silvery trails, ragged holes, vanished seedlings) and Growli will confirm slug or snail damage versus caterpillar, vine weevil or rabbit, then build you a 3-week protocol that fits your climate.
Why slugs and snails matter
Slugs and snails are gastropod molluscs. They feed by rasping plant tissue with a tongue covered in tiny teeth, and they thrive wherever it is damp, sheltered and cool. In the UK they cause more damage to ornamental and vegetable gardens than any other pest. In the US they are a bigger problem in the Pacific Northwest, coastal California, the Gulf Coast and the wetter Atlantic states than in the dry interior.
Common species to know:
- Garden slug (
Arion hortensis) — small, dark, eats both leaves and roots. - Grey field slug (
Deroceras reticulatum) — the classic seedling-shredder. - Keeled slug (
Milaxspecies) — burrows, hollows out potato tubers. - Spanish slug (
Arion vulgaris) — large, orange-brown invader spreading across northern Europe. - Garden snail (
Cornu aspersum) — the brown-shelled species, plus a notorious invasive in California citrus.
For host-plant context and ID help across other garden pests, see our garden pest identification guide and the dedicated /pests/slugs entry.
How slugs and snails damage plants
Damage is unmistakable once you know what to look for:
- Silvery slime trails on leaves, paths, pots and patio stone in the morning.
- Irregular ragged holes with smooth edges chewed through leaves — distinct from the sharper bites caterpillars leave behind.
- Seedlings vanished overnight with only stubs of stem left.
- Smooth grazing marks on ripening strawberries, tomatoes and courgettes near soil level.
- Tunnelled potato tubers caused by keeled slugs working below ground.
Worst-affected plants: hostas (the classic), delphiniums, lupins, dahlias, lettuces, brassicas, beans, strawberries, courgettes, and almost anything you grow from seed.
The 2022 UK metaldehyde ban — what changed
Before 2022, most "blue pellet" slug killers sold in UK garden centres contained metaldehyde, a chemical that paralyses slugs and slowly dehydrates them. The UK government and the Health and Safety Executive (HSE) acted on advice from the Expert Committee on Pesticides about risks to birds, hedgehogs, dogs and toads. The end result, as published on GOV.UK and confirmed by Defra:
- 31 March 2021: supply of metaldehyde products to end users ended.
- 31 March 2022: all outdoor use of metaldehyde slug pellets banned in Great Britain.
If you still have an old box of blue metaldehyde pellets in the shed, dispose of it through your local council's chemical waste route — do not use it outdoors. Across the US, metaldehyde remains EPA-registered, but it is the leading cause of slug-bait poisoning cases in dogs reported to poison control lines. Most US extension services now recommend ferric (iron) phosphate as the safer first choice.
Safety note: Always read the product label and follow manufacturer's PPE, dosage and re-entry guidance. Pesticide approvals change frequently — confirm via the UK HSE register or US EPA before use.
Ferric phosphate — the legal modern bait (UK + US)
Ferric phosphate (iron phosphate) is the active ingredient in modern slug pellets like Sluggo (US, OMRI-listed for organic gardens), Slug Gone, Growing Success Advanced Slug Killer and several supermarket own-label products in the UK. EPA records show it has been registered for pesticide use in the US since 1997, and iron phosphate is "Generally Recognized As Safe" (GRAS) by the FDA when used at label rates.
How it works:
- Slugs eat the bait, lose appetite, retreat to hidden spots and die over several days.
- You see fewer dead slugs lying out compared with metaldehyde — they die under cover, which is normal.
How to use it well:
- Scatter pellets thinly around at-risk plants in the evening, never in dense piles.
- Reapply after heavy rain — modern formulations are more rain-fast than older ones, but still degrade.
- Stick to label dose. Iron phosphate is far safer than metaldehyde around pets and wildlife, but ingesting large amounts can still upset a dog's stomach.
Safety note: Read the label, store sealed, keep dogs and toddlers out of treated beds for the recommended interval, and confirm current approval status via UK HSE or US EPA before buying.
Parasitic nematodes — biological control
Phasmarhabditis hermaphrodita is a soil-dwelling nematode that infects and kills slugs. In the UK it is sold as Nemaslug by BASF/Nemasys (a single dose treats 40 square metres for around six weeks). US gardeners have had limited access historically, but interest is growing and similar products are appearing for the organic market.
How to apply:
- Water onto moist soil when soil temperature is at least 5 °C (41 °F).
- Best spring and autumn when soil is warm and damp.
- Reapply every 6 weeks during the active growing season.
Nematodes target slugs preferentially (less effective on adult snails) and are completely safe for pets, children, hedgehogs and earthworms.
Non-chemical control that actually works
Stack two or three of these and most gardens stay below the damage threshold without any bait at all.
Night-time hand-picking
The single most reliable technique. Go out 30–60 minutes after dark with a head torch and a tub of soapy water. Check hostas, lettuces, the rims of pots, undersides of pot trays and the soil under low-hanging foliage. Two or three serious patrols in spring can flatten the local population for the season.
Copper tape and copper rings
Slug bodies react with copper and they get a mild electric-style shock. Copper tape (around pots, raised beds, greenhouse legs) and copper rings around hostas work well when clean and unbroken. Clean off oxidation and bird droppings each spring or the effect fades.
Beer traps
Bury a yoghurt pot or shallow container to the rim, fill it 2 cm deep with cheap lager. Slugs are attracted by yeast, fall in and drown. Empty and refresh every 2–3 days. Beer traps catch a lot of slugs but only over a small radius, so use them around prized plants rather than across the whole bed.
Rough barriers
Sharp grit, crushed eggshell, wood ash, sheep wool pellets and bran are all sold as slug deterrents. RHS trials and US extension reviews suggest the evidence is mixed — they slow slugs down rather than stopping them. Useful as a top dressing combined with other methods, not as a sole defence.
Encourage natural predators
Hedgehogs, song thrushes, frogs, toads, slow worms, ground beetles and centipedes all eat slugs. Practical moves: leave a wild corner, build a small wildlife pond, add log piles, skip slug-bait broadcast across the garden (it kills the predators' food supply), and keep cats out of the toad's territory.
Sacrificial crops
Chervil, comfrey and old lettuces left around the edge of a bed often pull slugs away from prized plants. Pair this with night hand-picking and you turn the sacrificial plant into a slug magnet you can clear easily.
Slug control by plant
| Plant | Worst risk | Best protocol |
|---|---|---|
| Hostas | Severe (#1 UK slug crop) | Copper rings + night picking + nematodes |
| Lettuce / leaf crops | Severe at seedling | Cloches + ferric phosphate around bed edge |
| Brassicas | Moderate after planting out | Hand-pick, mulch with sharp grit |
| Strawberries | Moderate on ripening fruit | Straw mulch off the ground + beer traps |
| Dahlias / delphiniums | Severe on new shoots | Nematodes in spring + copper rings |
| Potatoes | Tuber damage by keeled slugs | Lift early, rotate beds, avoid mulch heaps |
| Tomatoes (outdoor) | Light to moderate | Keep fruit trusses high off the soil |
Prevention going forward
- Water in the morning, not the evening. Damp beds at dusk are slug heaven.
- Tidy slug hideouts — flip pots, lift planks, clear stones around veg beds in late winter.
- Refresh barriers in early spring before slugs become active.
- Stack methods. No single tactic clears a hosta bed. Combine ferric phosphate + nematodes + night picking + copper for the gold-standard outcome.
- Pay attention to weather. Two warm wet evenings in a row trigger mass feeding — get outside on those nights.
Safety note: If a dog or cat eats slug pellets of any kind — including ferric phosphate — call your vet or, in the US, the ASPCA Animal Poison Control Center on (888) 426-4435. Take the product packaging with you.
Related articles
- Garden pest identification — complete guide
- Houseplant pests identification
- How to get rid of aphids on plants
- Companion planting guide
- How to grow lettuce
Reviewed and updated by the Growli editorial team. For questions about anything here, open Growli and ask — or email hello@getgrowli.app.
Frequently asked questions
Are metaldehyde slug pellets banned in the UK?
Yes. The UK government confirmed an outdoor ban on metaldehyde slug pellets from 31 March 2022 across Great Britain. Supply to end users ended on 31 March 2021. Any remaining stock cannot legally be used outdoors. Replace with ferric phosphate pellets (Sluggo, Slug Gone) or parasitic nematodes such as Nemaslug, both of which are far safer for hedgehogs, birds, pets and other wildlife.
What is the safest slug killer for pets?
Ferric phosphate pellets used at label rate are the safest commercial bait — the EPA notes they are relatively non-toxic around children and pets compared with metaldehyde. Parasitic nematodes (Nemaslug in the UK) are completely pet-safe. Non-chemical options like copper tape, beer traps and night hand-picking are also fully pet-safe. Keep all slug baits, even ferric phosphate, away from dogs that like to forage.
How do I stop slugs eating my hostas?
Hostas are the classic UK slug target. Stack four defences: copper rings or tape around the pot or crown, parasitic nematodes watered onto the soil every six weeks in spring and autumn, ferric phosphate pellets scattered thinly around the base, and a night-time torch patrol once or twice a week through April and May. Avoid evening watering, which keeps the soil tempting for slugs.
Do beer traps work for slugs?
Yes, beer traps reliably catch slugs because the yeast attracts them, but their pulling radius is small — a metre or two. Use them near prized plants rather than as your only defence. Bury a yoghurt pot to the rim, fill with 2 cm of cheap lager, empty and refresh every 2–3 days. Combine with copper barriers and night hand-picking for the best results in a damp UK or US Pacific Northwest garden.
Do coffee grounds repel slugs?
Evidence is mixed. Some studies show caffeine kills slugs at high concentrations, but garden-strength used coffee grounds give inconsistent results. The grounds also break down quickly. Use them as a soil amendment if you have them, not as a primary slug barrier. Copper tape, ferric phosphate pellets, parasitic nematodes and night hand-picking are all better supported by research and extension reviews.
What time of year are slugs worst?
Spring and autumn, especially after rain. In the UK, peak damage usually runs from April through June and again from September through October when soil is damp and temperatures are mild. In the US Pacific Northwest and Gulf Coast, slugs are active much of the year; in colder zones they crash in midsummer drought and again under hard frost. Plan your nematode applications and night patrols around those damp windows.
Are slug pellets safe for hedgehogs?
Old-style metaldehyde pellets were toxic to hedgehogs (one of the main reasons for the 2022 UK ban). Ferric phosphate pellets are far safer because hedgehogs generally avoid them and any small amount consumed via a poisoned slug is much less harmful. Even so, scatter pellets thinly rather than piling them, and never use them in a known hedgehog corridor. Better still, rely on nematodes, copper barriers and hand-picking in wildlife-friendly gardens.
How do I get rid of snails in my garden?
Snails respond to the same protocols as slugs — ferric phosphate pellets at label rate, hand-picking on damp evenings, copper barriers, and removing daytime hiding spots like upturned pots, board stacks and weedy edges. Parasitic nematodes are less effective against adult snails than against slugs. In California citrus and Mediterranean climates, focus on physical removal plus copper bands around trunks.