🐛✗ Tested and false“Traditional blue metaldehyde slug pellets are still fine to buy and use in UK gardens.”
Metaldehyde slug pellets were withdrawn from sale in the UK from 31 March 2021, and it became illegal to sell or use existing stock from 1 April 2022. The decision followed advice from the UK Expert Committee on Pesticides and the Health and Safety Executive that metaldehyde poses an unacceptable risk to birds, mammals including hedgehogs, and other wildlife exposed to treated slugs, soil or water. Ferric phosphate is now the only slug pellet active ingredient legally available in the UK.
What to do: Check the label before buying pellets: only ferric phosphate (sometimes listed as iron phosphate) products are legal. Any pellet claiming to contain metaldehyde should not be used and, if you find old stock, should be disposed of rather than applied.
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- Garden OrganicMetaldehyde slug pellets were banned from sale and use in the UK from 2021 to 2022 because of documented harm to dogs, birds and hedgehogs, and ferric phosphate pellets are now the legal alternative.
“Every slug or snail you find in the garden is a pest eating your plants, so the more you kill on sight, the better.”
The UK is home to more than 40 slug species and 100 or more snail species, but only a handful regularly feed on living garden plants, including the netted field slug, brown soil slug and common garden snail; most others mainly recycle dead plant material and are themselves food for birds, hedgehogs and frogs. Oregon State University Extension makes the equivalent point for its region: several native slug and snail species found in gardens do not damage garden plants at all.
What to do: Focus control effort on seedlings and soft new growth, where the actual plant-feeding species cause the most damage, rather than treating every slug or snail in the garden as a threat to be destroyed.
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- RHSOf the UK's many slug and snail species, only a small number such as the netted field slug, brown soil slug and common garden snail regularly damage garden plants, while most are beneficial decomposers and prey for garden wildlife.
- Oregon State University ExtensionSeveral non-native slug and snail species cause garden damage, but native species such as banana slugs and Pacific sideband snails do not damage garden plants.
“Sprinkling used coffee grounds around plants repels or kills slugs”
Washington State University Extension's fact sheet on coffee grounds states plainly that there is no published evidence coffee grounds repel or kill garden pests. Dry grounds don't reliably deter slugs, and damp grounds can even add surface moisture and organic food that draws them in. Caffeine itself is toxic to slugs, but only at concentrations from a liquid drench, not from scattering used grounds.
What to do: Don't rely on spent coffee grounds as a slug barrier. Use tested non-chemical methods (physical barriers, nematodes, encouraging predators) instead.
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“Ferric phosphate (iron phosphate) slug pellets are completely safe for hedgehogs, birds and other garden wildlife.”
Ferric phosphate pellets are approved for organic growing and carry far less risk to mammals and birds than the now-banned metaldehyde formulations. However, official advice does not treat them as risk-free: guidance on garden wildlife states that even organic slug pellets have been shown to have negative effects on wildlife in the garden, and many ferric phosphate products include chelating agents such as EDTA, added to make the pellets more effective, which can also harm earthworms.
Our read The safety gap between ferric phosphate and metaldehyde is real and worth acting on, but "safe" overstates it: these are still pesticides with some non-target impact, not an inert deterrent.
What to do: If you use pellets, apply them sparingly (a light scatter rather than a heavy handful) and only where damage is actually occurring, and lean on non-chemical controls as the first line of defence.
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- RHSSlug pellets, including organic ferric phosphate ones, have been shown to have negative effects on garden wildlife, and the advice favours encouraging natural predators and other cultural controls instead.
- Garden OrganicFerric phosphate pellets work by disrupting calcium metabolism in molluscs, are less harmful than metaldehyde, but often contain chelators like EDTA that can damage earthworms, so should be used very sparingly.
“Slugs and snails only come out and feed at night, so checking plants during the day won't reveal a problem.”
Slugs and snails are predominantly nocturnal, and most feeding does happen after dark, which is why torchlight checks in the evening are the standard way to find them in the act. But extension research adds an important exception: Colorado State University Extension notes slugs occasionally stay active on overcast or rainy days, not only at night.
What to do: Do your main slug and snail patrols after dark or at first light, but also check likely daytime hiding spots (under pots, boards, mulch, dense foliage) on cool, overcast or wet days, when slugs may still be moving and feeding.
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- RHSSlug feeding mainly happens at night, so slime trails and leaf damage found in the morning are usually the first evidence, and torchlight searches after dark are recommended for hand-picking.
- Oregon State University ExtensionSlugs feed at night when temperature, wind and humidity are favourable, and retreat to dark, moist hiding places such as under mulch and leaves during the day.
- Colorado State University ExtensionSlugs feed mostly at night, although they occasionally are active on overcast or rainy days.
“Hand-picking slugs and snails off plants, especially by torchlight in the evening, actually makes a difference.”
Extension services list hand-picking as one of the more reliable non-chemical controls, provided it is repeated regularly rather than done once. Oregon State University Extension recommends checking plants about two hours after sunset or in the early morning with a torch, and trapping slugs under boards for daily removal.
What to do: Patrol vulnerable beds after dark or at first light several times a week during mild, damp weather, and dispose of collected slugs in soapy water rather than tossing them over the fence, where they can simply return.
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- Oregon State University ExtensionHand-picking slugs about two hours after sunset or in the early morning, along with trapping them under boards for daily removal, is recommended as a control method.
- RHSTorchlight searches on damp evenings are recommended as a hand-picking method for controlling slugs and snails.
“Slug and snail damage gets noticeably worse after rain or during extended wet spells, so that's when to watch plants most closely.”
Slug and snail movement and feeding both depend heavily on moisture. Colorado State University Extension notes that slug population levels track a garden's moisture conditions directly, and Oregon State University Extension times its recommended start to slug control to autumn, after the first seasonal rains begin, because slugs need damp conditions to move about and lay eggs.
What to do: Step up monitoring, hand-picking or pellet use in the days after rain or during prolonged mild, wet spells, since that is when slugs are most able to travel and feed; dry spells give plants more of a breather.
In Scotland: Scotland's generally cooler, wetter growing season compared with much of England and Wales means this wet-weather vigilance window tends to run longer and recur more often through spring and summer.
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- Colorado State University ExtensionThe level of a slug population depends on the moisture conditions in a garden, and slugs are occasionally active on overcast or rainy days.
- Oregon State University ExtensionSlug control efforts are recommended to begin in autumn once the first rains arrive, because slugs and snails lay their eggs and become more active as the rains begin.
