How To Control Slugs & Snails in Your Vegetable Garden

Knowing How To Control Slugs & Snails in Your Vegetable Garden Is Gardening’s Holy Grail. And One Most People Fail At. This is How to Succeed At Slug & Snail Control

There are many myths, legends, rural folklore, smoke and mirrors when it comes to How To Control Slugs & Snails in Your Vegetable Garden. The majority of them don’t work for amateurs or professionals and that is why slug damage costs farming well over £100 million a year. PLUs all the damage it does to garden veg, fruit and ornamentals.

Slugs & Snails: The Facts

Let’s start with some facts.

Not all slugs and snails are harmful to our plants. Many eat a wide range of organic matter and are great at devouring decomposing organic matter. These species are a welcome addition to any compost bin, though I’ve yet to find many people to praise them for it.

Slugs and snails aren’t the same. Snails are the ones with the shells and slugs are teh ones without shells.

Slugs and snails love wet weather and hate to much hot dry weather. Because they need to prevent drying out they prefer wet weather and breed faster at this time. They also favour mild winters as fewer are killed by the cold.

Slugs and snails are hermaphrodites. They are neither male or female but have the sex organs from both genders. Normally it takes two to tangle and both will go away and lay eggs, but they sometimes fertilsie themselves!

Snails usually first mate at one year old and often live for up to 5-7 years. But some species can live for 25 years. There’s more on slug ecology at the end of this post.

In many countries, snails are eaten as a gourmet delicacy. In France escargot (snails) are farmed. And at a rural bar I used to frequent in Portugal the barman used to collect snails from his olive plantation and prepare them with olive oil local herbs and they were delicious with a cold beer. They were as popular there as pork scratchings or crisps are in the UK.

Some slugs spend most of their lives underground and rarely surface unless it is raining or very wet.

Seven Ways to Control Slugs and Snails in Your Garden .. Well Maybe

One problem when trying to understand what works is that when we do something and get no slug or snail damage we believe what we did was the reason. Of course the real reason might be totally different. Maybe it was too cold or dry and they didn’t come out. Or they preferred to eat some roots underground and you didn’t see them.

Proving something works is hard whilst proving it doesn’t work is much easier.

Sharp and Rough Surfaces

I often read that slugs are deterred by brambles and other sharp things …. but this video shows that they are quite happy to crawl over razor blades.

Eggshells

Many people swear by eggshells. they claim snails will not climb over them. Watch this video and see if you still believe it.

How About Coffee Grounds, Diatomaceous Earth & Paprika?

I hear people say coffee grounds stops slugs. It apparently stops them in their tracks as they hate caffeine. And apparently paprika burns them and diatomaceous earth dries them out.

The only problem is that slugs don’t know this. They don’t teach it at slug school. So lets watch what happens when the slugs are confronted with these “proven methods” of slug control!

So that doesn’t work.

Copper Tape

I’ve just watched another video where the presenter extolled the virtues of copper tape. Apparently slugs get an electric shock if they touch it. Its meant to be a bit like biting on a piece of silver foil with a filling .. agghhh.

The only problem was this was a video of a presenter telling us what works .. there were no slugs involved to vote with their slime. And I know that slugs just slide right over the copper tape. Here’s the proof on video.

And if you’ve seen videos where copper tape is working look behind the scenes to see if they have connected to copper tape to a strong battery. that works for few hours until the battery dies.

Copper Coins

One American video presenter explained how copper coins worked. It’s a great story .. but where do you get copper coins from? Some coins are copper plated but its a very thin layer and wears off in weeks of handling.

Ohh and you have to place a ring of coins around each plant without gaps between them!

Electric Fences

Apparently you need to run a electric wire at slug height and zap them with a good pulse. Well 240 volts would deter me. Having used electric fences for cattle I know they can work but at snail and slug height they touch the soil or plants and short out.

And I’m sure the toads, frogs and hedgehogs that help me by eating slugs might be deterred as well!

So we’ve listed lots of things that don’t work, and I could list many more, So What Does Work?

How To Control Slugs & Snails: Effective Slug & Snail Control Methods

Hedgehogs, Badgers, Ground Beetles, Frogs, Toads, Slowworms, Rove Beetles, Glowworm Larvae, Mice, Centipedes, Blackbirds, Mistle Thrushes and Song Thrushes All Control Slugs and Snails The Natural Way

Let’s start with snails. They are eaten by blackbirds, mistle thrushes, song thrushes, the larvae of glow worms, hedgehogs, toads, centipedes and mice. Snails are predated by ground beetles, rove beetles, frogs, toads, slow worms and hedgehogs.

All the above need protecting in the garden. Keep them safe. They are gardener’s friends.

Keep Your Garden Tidy

A clean tidy garden leaves fewer places for slugs and snails to hide. So ensure the grass is cut short (wildflower meadows are an exception .. but might still harbour slugs. You have to balance pros and cons here).

Don’t leave pots, logs, pieces of wood etc lying around. They harbour slugs and snails and encourage them. It’s why I’m a bit sceptical about raised beds. They have advantages but also tend to have lots of hidey holes for slugs and snails.

If you do have to store pots or whatever in a corner of the garden then check them over every few weeks and remove any slugs and snails they harbour. This is even more important in winter and early spring, as its this time of year when you can remove huge numbers that are overwintering,

Provide Shelter to Slugs and Snails .. To Trap Them

The exception to keeping clean and tidy is to purposefully provide some shelter to encourage the slugs to hide during the day. Then you can check every day to collect and destroy any slugs and snails. I tend to use flat “radiator” stones near heat-loving plants as they solve two problems at once. They act as a heat sink to keep plants warm AND somewhere where slugs hide and can be caught.

Beer Traps & Slug Pubs

Two names for one solution! Slugs and snails love beer. Part bury a container in the soil, into which you’ve punched some holes, with an inch or so showing as this prevents beetles etc falling in, and the slugs will be attracted. They then fall into the tap and drown in the beer.

Old recyclable coffee cups can also be used, but if it rains the beer gets diluted.

Garlic Wash

I’ve not personally tried this and can find little research to back it up BUT nor can I find any verifiable reports of slug damage on garlic. So I can only conclude that slugs don’t like garlic. But whether that dislike is enough to dissuade them from eating crops spayed with a garlic wash I can’t say.

As for whether it can kill slugs again I have no experience of this. However, I’ve added garlic wash to this section as I believe it highly likely to work at some level, if not very well. Watch this space for updates.

Slug Nematodes: Natural Organic Slug Control

The slug nematode (Phasmarhabditis hermaphrodita) is a facultative parasite widely found in the soil and leaf debris. As a biological molluscicide / bio-pesticide, it infects slugs and can go into a dormant stage if conditions don’t suit it.

It is supplied, adhering to clay particles or in a gel, in the dormant stage which is called dauer larvae. This is then diluted with water and can be sprayed onto the soil and crop. It can then infect slugs and tends to kill them about 7-21 days later. In lab experiments, they stop 90% of slugs from feeding after four days As dauer larvae they are about 1mm long so just visible to the naked eye.

When the parasite enters the slug it changes into a hermaphrodite, self fertilise and spread rapidly through the host.

Once the host slug dies the parasite reverts back to the larval stage and the cycle starts again.

Phasmarhabditis hermaphrodita is a bacterial feeding species, though not normally specific in its symbiotic bacterial associations. When sold commercially it is however normally reared in monoexenic conditions with Moraxella osloensis.

Moraxella osloensis is sometimes found in the nasopharynx of adult people and at least one case of infections in children has been reported. There is however no record of it being transmitted from slugs or Phasmarhabditis hermaphrodita and it’s normally regarded to be of no danger to humans and is susceptible to susceptible to penicillin, cephalosporins, aminoglycosides, and trimethoprim-sulfamethoxazole 

Pros and Cons of Using Phasmarhabditis hermaphrodita

Advantages of using Phasmarhabditis hermaphrodita

Natural and organic

Very effective

Very selective, infects no other species

No effective on earthworms, bees or other insects

Can be purchased and stored in dormant stage

Well tried and tested in Europe since 1994

Non toxic

Disadvantages of using Phasmarhabditis hermaphrodita

Expensive

Needs to be used in advance

Needs minimum temperatures to be effective.

Chemicals: Methiocarb, Metaldehyde & Ferric Phosphate

 Metaldehyde and methiocarb were the standard accepted treatments for slugs in both agriculture and commercial horticulture. Methiocarb was banned in 2015. The recommended slug pellet ingredient to use now is ferric phosphate which kills slugs by giving them an iron overdose. Iron is essential to health … even humans need it or we get anaemia. Apparently slugs tolerate overdoses more than other species. We have to remember than most “chemicals” are toxic in excess. We can die from drinking too much water! But yes, in essence, ferric phosphate is relatively safe and I can find no toxicity reports relevant to hedgehogs. However, a lot of sites still demonise slug pellets without realising that products like methiocarb are no longer used.

As for metaldehyde. I doubt much has been used for a year or more in agriculture because the producers scaled back production before the ban took effect. They didn’t want stock they couldn’t sell.

HOWEVER, following a judicial review, the ban on metaldehyde was lifted.

The ban has now been reimposed and metaldehyde is now banned for outdoor use. it is howevervlegal to use in grenhouses . So watch out for those misleading headlines.

I frequently see comment that ferric sulphate is toxic to earthworms. I can’t t find a lot of verifiable evidence on this. One piece of research showed problems when ferric sulphate was used at 35 times the recommended rate. Thats unlikely to happen on farms but could in gardens as gardeners tend not to measure their slug pellets or area.

I noted one other piece of research where the test was conducted over 48 hours and used 8 times the recommended dose . These tests are indicative but not conclusive regarding normal usage.

Slug Ecology

Slugs are gastropods and there are as many as 46 species in the UK and only 4-5 cause any damage that has an economic impact. The most common slugs are from the Milacidae, Deroceras and Arion species. Slugs are active all year round but are most often seen on the surface when it is damp and warm. These surface-level slugs tend to feed mainly at night so we don’t see levels unless we hunt them down by torchlight. However, species such as the keeled slugs (Milax species) are very small and live deep underground and do the highest level of economic damage to potatoes and other underground root crops. They can do this when conditions on the surface are inclement. Adults slugs can lay up to 400 eggs in a year, often in spread over the year with 5-6 laying periods, which means that when conditions are right the population can expand exponentially. The eggs are most usually seen as clusters of small spherical yellowish-white eggs which as laid under stones, pots, logs etc. They hatch once the temperature rises above 5C.

More on Slug Biology

Slugs and snails are gastropods which by definition means they have are single shelled soft bodied molluscs. Most slugs however have lost their shell or it is so reduced as to not be visible.

The Grey field slug  (Deroceras reticulatum) is usually about 5 cm long whilst the large black slug (Arion ater) is about 12 cm long when fully extended.

Lastly let me address an issue that is often asked. Can slugs smell food sources. In most cases it seems not. Of those tested their food hunting strategy seems to be to blunder along until they bump in to food, then devour it. They seem not to follow old slime trails or sniff out food.