Aaargh, slug armies! We’re sure most vegetable growers understand the pain – you’ve planted your seeds, cared for them, nurtured them, watched them sprout and grow – it’s a relationship that time, energy, and love have gone into. Then overnight that life you’ve helped bring into existence is gone, victim of the unrelenting slug, leaving nothing but a slime trail behind.
We’re currently fighting the slug hoards, we’ve scoured the web, called the old hands, and are testing various solutions. There are a lot of tips out there on how to fight these crawling stomachs. The reality it seems is that no single method will solve the problem. Slug overpopulation is caused by an imbalance, a lack of predators that keep the population of slugs under control. The solution is to create an ecosystem that will help maintain a balance.
But first, let’s look at some slug characteristics so we know what were dealing with:
- Slugs love moisture and water.
- Slugs are nocturnal, during the day hide underneath flowerpots, stones, leaves etc. coming out at night when it’s cooler and damper.
- Slugs are nomads, unlike snails who carry their home on their back but, if deported less than 20m away, will come back to the same spot.
- Because they have no skeleton they can squeeze through the tiniest holes.
- Slugs eggs are gelatinous, mostly pale and can be found in small clusters under rocks, in plant pots, or in similar ‘safe’ locations.
So now we have some idea of what we’re dealing with, so let’s look at ways we’ve heard of to deal with them:
Correct the imbalance
Before we start trying to get rid of them, let’s remember that slugs have a role to play in the ecosystem. As well as being excellent recyclers, they eat the weakest plants first. So they play a role in strengthening your plant gene pool. A slug plague is an indicator of a lack of predators but also of a soil lacking nutrients. Plants need these nutrients to build defenses.
Slugs of course, have their own place in the ecosystem, providing food for predators higher up the food chain. So let’s start by looking at these:
- Birds: Thrushes and blackbirds are both slug eaters, so provide an environment that attracts them.
- Beetles: Carabid beetles such as the Violet Ground beetle and Common Ground beetle are very effective slug predators, both the larvae and beetles eat the eggs and the tiny slugs. If suitable homes are provided they can appear in large numbers. Some patches between your beds with tough grasses or sedges, some straw or hay in an upside down plastic box (you can wrap the boxes with some fine mesh chicken wire to keep mice out that eat beetles), some stones for them to live under, raised beds, and well drained soil are all good.
- Centipedes: As carnivorous nocturnal hunters, they are perfectly adapted. Learn to distinguish between the millipedes and centipedes, as millipedes are herbivores and love young seedlings. Centipedes like it moist, living in leaf litter, under stones, in rotting wood, etc.
- Toads: Toads do not need a pond. If you provide enough moist hiding spaces they will most likely be attracted by the abundance of food.
- Slow Worms: These wonderful creatures are rare and strictly protected. You should not capture them from the wild so the only way to get them in your garden is to provide a good shelter and hope they turn up. If you have them, protect them well; they are a great ally.
- Hedgehogs: It is a debatable issue whether it is ethically justified to keep them in the perimeter of a large garden. If the hedgehog would otherwise have been culled and has a large enough habitat that is also able to provide it with all the essentials it needs, I think it may be justified.
- Shrews: to attract shrews you need ground cover. Shrews spend much of their time foraging in long grass, among leaf litter or under logs, but rarely coming out in the open.
- Pondlife: Having a pond in the garden has many benefits. It will allow birds and insects to drink. And you can grow food and flowers in the pond and on the edge.
- Ducks: are great slug predetors, and some breeds can even be trained to go ‘huntng’ with you.
- Frogs: If you don’t keep fish, newts, ducks or herons, you can keep frogs.
Prevent by discouragement
- Watering times: A dry garden at night time can reduce slug damage significantly. If you need to water, consider doing so early in the morning instead of the evening. It is estimated that this can reduce the damage by 80%.
- Decoy plants: There are plants out there that slugs like even better than your vegetables. If you grow these, they will attract the slugs and all you will need to do is pick them up at dusk or put a slug trap nearby. Lawn Camomile is a good one; being a perennial, it is already in full swing in sping, making it especially effective at the time when seedlings are small and most vulnerable. Some people also report good results with bok choi and Chinese cabbage. Rubbing the plant whilst looking for slugs releases the scent which will attract the slugs. If you water the decoy plants in the evening but not your crop, it might further reduce the damage even higher than the above mentioned 80%.
- Slug repellent plants: there are also plants that slugs don’t like; chives seem quite effective and are also easy to grow. Surrounding your vegetables with a planting of slug repelant plants can be an effective deterent.
- Copper: Slugs don’t like contact with copper, so this can be an effective barrier. A ring of pennies around a seedling, stripped electrical wire wrapped around a pot or the legs of a potting table, there are many ways to implement this method.
- Mulches: There are many things that I’ve heard of people using, egg shells, sharp sand, coffee grounds, etc. The idea is that slugs don’t like the slide over sharp edges. However, these methods only seem to work when the mulch is dry, so as soon as it rains – when slugs are more likely to be out anyway – your effort goes to waste.
- Pine: Slugs hate pine, so spraying the outside of plant pots and raised beds with pine essential oil can act as a natural deterrent. (We’ve read some articles suggesting that a pine needle mulch can help keep slugs away. This isn’t a great idea: conifers, such as pine trees, contain compounds which inhibit the growth of other plants (this is why they tend not to have other species of plants growing under them) and pine needles have an inhibitory effect on the germination of other seeds.
- Deportation: While this may seem kinder than killing them, in essence what you are doing is transporting an imbalance from one ecosystem to another, thereby creating a problem elsewhere.
- Beer traps: The slugs are attracted by the fermentation gasses of beer, so use a beer that has good fermentation; Guinness seems to be a good one. Slugs seem to get drunk and forget to crawl out again and drown. Be aware that other creatures fall in sometimes too, especially the predator beetles mentioned above- they don’t get drunk and do want to get out again – so don’t forget to include a stick as an exit ladder.
- Other traps: Grapefruit halves, flower pots, cardboard, anything dark and moist will be favoured by the slugs as a hiding place during the day. They can then be collected for destruction.
- Sharp implement: Using a sharp knife or scissors to flick the slugs off a plant onto the soil surface and behead them, leaving them as food for other predators. If you are going to kill them this is at least a quick death.
One thing you want to avoid is completely culling your slug population. By eliminating all the slugs, we are also taking away food for the predators that eat the slugs or its eggs and we drive away the predators in a search for food. The result of that is that we create the perfect scenario for a new slug plague: An area rich in food for slugs with few predators. Party time! In effect we become addicted to the temporary cure. Here are some other ‘cures’ to avoid:
- Salt: Pouring salt around your plant will keep the slugs off, but it will also affect your plants and may even kill them.
- Slug pellets: There are many reasons to avoid these: besides the reason mentioned above, pellets contain things that are not healthy for their environment; even organic pellets often contain iron phosphate, which is harmful to earthworms.
- Diatomaceous earth: Kills all insects including those that feed on slugs. It is also only effective in dry weather, in rain it dissolves; slugs are worst in wet weather, so this is a serious waste of resources.
- Nematodes: Nematodes are microscopically small worms that parasitize and kill slugs. An infected slug stops feeding within 3 to 5 days and then displays a typical swelling. The nematodes multiply inside the slug and when it starts to decompose, a new generation of nematodes spreads and starts looking for the next prey. The nematodes work for up to 6 weeks. Nematodes are a very effective short term treatment, but will result in the situation mentioned above.