Slug pellets: organic options, toxicity & how to use them correctly


As a child, I played every day in the garden in front of my house in my home town of Rheinlandpflanz. There, my interest in nature grew, as did my aspirations to become a natural scientist. I now study horticultural phytotechnology and am currently writing my bachelor’s thesis on the topic of crop protection in orchards. Since living Berlin, I have become particularly interested in improving the quality of life in cities with the help of plants.

Favourite fruit: figs, passion fruit, berries, limes and oranges.
Favourite vegetables: potatoes, garlic, tomatoes, pickles, lamb’s lettuce and rocket.

Slug pellets against slugs in the garden is an efficient way to protect its fruits and vegetables. Organic slug pellets are also gentle on beneficial insects and pets when used properly.

slug pellets in garden with slug
Slug pellets prevent slug damage in the bed [Photo: Heiko Barth/]

Snails, especially slugs, are really voracious little animals. But no garden need be at their mercy without protection. One option for plant protection is the application of slug pellets. This was long discredited because its old conventional active ingredients are harmful to the environment and toxic. But not all slug pellets are the same. There are different preparations with different properties. Below you will learn everything about the mode of action and application of slug pellets against slugs.

What types of slug pellets are there?

Most slug pellets now contain ferric phosphate. Ferric phosphate is a natural substance permitted for use in organic farming and poses no danger to humans, garden wildlife, soil microorganisms or pets. You can also get granules containing essential oils

Up until recently, metaldehyde was one of the most common active ingredients in slug pellets. However, as it is harmful to garden wildlife and the environment, metaldehyde was banned in the UK in April 2022. Methiocarb was also still approved until 2014, but due to its strong toxicity, this agent is also banned and not permitted for use in the UK. If you still have old methiocarb slug pellets, be sure to dispose of them safely.

Note: a use-by period of 18 months applies to plant protection products that are no longer authorised. After that, they must be carefully disposed of at disposal companies or collection points of the counties or municipalities.

Watering slug covered plant with protection
Before using plant protection products, always read the label carefully [Photo: New Africa/]

How do slug pellets work?

Depending on the active ingredient, slug pellets have different modes of action. We present the three different variants.

Essential oils

The snail granules with essential oils drive away the snails by its scent. It is therefore a repellent. They are not killed, however, the snail problem is merely transferred to another garden. It can be effective to apply the repellent together with a sacrificial bed: Everywhere where slugs are to be driven away, the fragrant deterrent is distributed so that all creepy-crawlies stay only in the sacrifice bed. Because the slug concentration there is very high, beneficial insects such as hedgehogs will soon be on the scene, and they like to hang out there. For example, geraniol, lavandin oil, and oils extracted from common lantana (Lantana camara) and mint (Mentha) are effective. Humans and mammals are not endangered when it is used properly, but side effects on other non-target organisms and beneficial insects as well as occasional plant damage could be observed in some cases.

Snail on a mint plant
Concentrated mint oil can scare away snails [Photo: Elmonir-press/]

Slug pellets with ferric phosphate

Slug pellets with the active ingredient ferric phosphate are available and are safe for garden wildlife, small children and the environment. After ingestion of this agent, the snails stop feeding, retreat to their hiding places without forming slime and die there. Thus, the dead animals do not lie around in the beds. The iron III phosphate is dissolved by microorganisms and organic acid and does not harm the soil, but is used as a plant nutrient.

Slugs on a log
Snails that have ingested Iron(III) phosphate hide [Photo: Sergey/]

How long does it take for slug pellets to work? When slugs ingest slug pellets with ferric phosphate, they immediately stop feeding, retreat to their hiding place and starve to death after several days. This substance acts for up to 2 weeks. The grain with essential oils immediately acts as a repellent. This means it deters the slugs without harming them. According to the manufacturer, the effect lasts up to 3 weeks, depending on weather conditions.

Slug with Iron pellets
Slug pellets with Iron(III) phosphate have the best environmental compatibility [Photo: Bernd Lang/]

The correct application of slug pellets

All variants of slug pellets are spread over a wide area and never in piles. Barriers around entire beds or surrounding individual plants with ferric phosphate-based slug pellets would also be less effective. Grain with essential oils, on the other hand, can be spread around beds as protection.

If slugs are found in the garden, caution is advised. Because these snails, which are protected by law, also die after ingesting the slug, which is something you want to avoid. However, since they are rarely in the treated vegetable beds, this is usually not a problem.

Slug and blue pellets
Slug pellets are granulated pesticides [Photo: Lisa-S/]

A typical application process for slug pellets:

  • Application in mild weather in the early morning or late evening.
  • Pour area beforehand so that the grains can swell
  • Spread slug pellets evenly around the plants to be protected without forming piles
  • Application rate: 38 grains per square metre
  • Application span: April to September (Maximum 4 applications at least 7 days apart).
  • No waiting time until harvest
  • Caution: Do not use on slugs in vegetable beds

Are slug pellets poisonous?

As with any pesticide, care must always be taken to ensure that non-target organisms do not consume the substance. As previously mentioned, slug pellets containing the active ingredient metaldehyde or methiocarb are poisonous to humans and animals, but these are no longer permitted in the UK. Even just a very small amount of these substances can be harmful to garden wildlife, pets or young children. If you happen to have any old packets of slug pellets containing these ingredients, we advise disposing of them in the correct manner.

Iron III phosphate, on the other hand, is gentler on beneficial insects and pets. It is also classified as non-hazardous to bees when used properly. Therefore, it is also approved for organic farming.

A cat in the garden
Old, metaldehyde-based slug pellets were toxic to pets, but are now banned in the UK [Photo: jamaludinyusuppp/]

What are the alternatives to slug pellets?

There are a variety of slug resistant and slug repellent plants. Likewise, slug fences and traps, as well as some home remedies such as coffee grounds for slugs can be helpful. Encouraging beneficial insects is also profitable for the entire garden. For a complete overview, see our article on control of snails.

Alternatives summarised:

  • Snail fences
  • Traps
  • Adapted planting
  • Promotion of beneficial insects
Snapdragons are avoided by snails [Photo: Cristina Ionescu/]
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