Hardly any other insect repellent divides opinions as much as slug pellets. The molluscicide is not only said to be lethal to slugs, but also toxic to mammals, especially hedgehogs, dogs and cats. Humans, especially small children, are also said to suffer symptoms of poisoning from slug pellets and are even said to be fatal when used in excessive amounts. However, not every product listed under this name is the same, and the various ingredients have different effects on organisms.
What is slug pellet?
Slug pellet is a molluscicide (chemical agent against mollusks) that is spread in the garden and is consumed or touched by the slugs. After the agent is ingested by the slug, the active ingredients absorb into the organism and cause it to die. The composition of the slug pellet is such that the mollusks are strongly attracted to it and literally flock around it. However, this is where the problem presents itself. Slugs are readily eaten by other mammals and birds, which then absorb the agent into their digestive tracts. Depending on the active ingredient, this ends fatally, so the two main active ingredients must be compared.
- Ferric phosphate
The agent is obtained mainly from these two substances and then processed into small beads, a granule, as remains in the soil of the vegetable bed for a long time. However, depending on the active ingredient, this must be redistributed, as it can be washed away by rain.
Iron III phosphate
Iron III phosphate is a chemical compound that appears in nature, for example, as the mineral strengite. It is also released from phosphate-containing fertilizers as soon as they come into contact with water. Ferric phosphate is obtained from iron in reaction with other substances, for example phosphoric acid, and is harmless to mammals and birds. Even when consuming high quantities of slug pellets based on ferric phosphate, there are no negative effects for dogs, cats and humans, even small children do not suffer. Nevertheless, there is of course a risk of choking here, should children put the grain in their mouths.
The following manufacturers offer products containing ferric phosphate:
- Biomol from Bayer Garten
- Ferramol from Neudorff
Mode of action
Iron-III-phosphate has a toxic effect on the slugs and ensures a so-called feeding stop, by which the animals stop eating the lettuce. As soon as the snail has consumed enough of the preparation, it retreats into its burrow and dies there. It does not slime and no longer poses a threat to birds, hedgehogs or other creatures.
Other advantages are:
non-toxic to bees, ground beetles and other beneficial insects in the garden
does not affect the quality of the harvest
Depending on the manufacturer, different compositions of the active ingredient can be found, but they basically act the same. A great advantage of slug pellet is the ability to use it throughout the season, because the phosphate does not adversely affect the quality of the soil and, consequently, the plants. You do not have to collect dead slugs by themselves, they are decomposed by natural processes in their shelter and are thus easily removed from the way. The most important thing here is to distribute them in the spring, before the snails can reproduce.
Note: Iron III phosphate, unlike metaldehyde, is approved for organic farming and gardening. This means you don’t have to worry about your plants or pets if you want to stop slug damage.
Metaldehyde is where you’ll find the real culprit for the common question of whether slug pellets are really toxic. Metaldehyde is derived from sulfuric acid and is highly flammable, killing slugs within minutes. It is therefore also used as fuel for camping (Esbit). But the substance is not only toxic to snails. Small mammals such as hedgehogs or domestic cats and birds can suffer symptoms of poisoning even when ingested in small quantities and subsequently die. This can also be observed in humans and, depending on the organism, different doses are found to be lethal.
- Adult humans: 4 g (about one Esbit tablet)
- Infants: 2 g
- Dogs: 0.2 g to 0.6 g depending on the breed
- Cats: 0.2 g
- Small animals and rodents: 0.1 to 0.2 g
Mode of action
In birds, a long-term effect is more likely to be seen; in mammals, the remedy works immediately. Snails begin to slime within minutes of oral ingestion. After only 20 minutes the snail is dead and must be collected by you individually, so that other animals do not eat it. The symptoms of poisoning by metaldehyde are dizziness, visual disturbances, irritated mucous membranes, onset of convulsions up to respiratory distress, coma and finally death. Depending on whether the poison reaches the digestive tract, this occurs in a period of 15 minutes to 24 hours.
The following properties can be seen with metaldehyde:
- deforms in rain
- can be washed away
- kills snails immediately
- tastes slightly sweet, therefore interesting for children and animals
- especially bad if spread incorrectly in the garden
- waiting time before harvest, otherwise poisonous
Therefore, for the above reasons, do not use slug pellets whose base is metaldehyde, as this does more damage. Although the slugs die immediately and cannot do any more damage, the risk is too great that accidentally small children or pets come into contact with the agent. Because of the aromatic substances, children in particular may mistake the granules for candy or something similar.
Note: Slug pellets have such a bad reputation due to a witness report of a deceased hedgehog that ate a slug that had previously ingested metaldehyde. The extremely high amount that the hedgehog ate in the process was due to improper distribution by the user, who offered the slug pellets via a rain-protected container.
Harmful to useful slugs
Slugs are considered harmful in the garden by many gardeners, but few know that there are also beneficial slugs. These systematically proceed against the harmful snails, either killing them directly or feeding on their eggs. Similarly, numerous species of snails can be found in the garden, which are not at all interested in vegetables or fruits and eat other food.
Ribbon snails (Cepaea)
Roman snail (Helix pomatia): is under nature protection
The tiger snail in particular is a welcome guest in the garden, as it specifically hunts the slugs that prey on the plants.
- Spanish slug (Arion lusitanicus)
- Field snail (Deroceras reticulatum)
- Garden path snail (Arion distinctus)
The pests can be recognized mainly by the fact that they do not have a house. Except for the Roman snail and ribbon snails, the tiger slug also has no house, but it can be recognized by its characteristic coloration, which has given it its name. While slugs behave predatorily, vineyard snails and ribbon snails eat rotting plant material and the eggs of pests. Therefore, they are also very helpful in the garden. For this reason, the general use of slug pellets is not recommended if many of the other slug species are in your garden. Therefore, only rely on the slug pellets in case of a really big plague.
If slug pellets in general seem too dangerous or toxic, you can find a variety of alternative home remedies that are much gentler. While ferric phosphate is not toxic or harmful, it can greatly reduce the number of beneficial insects because the grain is never selective.