Does Organic Slug Control Really Work?

What are slugs and their role as a garden pest

Slugs are garden pests that can do a lot of damage in a short period of time.  In today’s testing garden assumptions series video I am going to go through the most commonly recommended methods to manage slugs and how I am planning to manage them in my garden.

There is a wide variety of critters that fit under the term slug.  Slugs usually feed on decaying materials however to do feed on live plants such as my squash, bean, leafy green seedlings, in some cases killing the seedling in a matter of a few hours.

They can expand to other crops such as carrots, strawberries peas and cabbage families if that is the only food source available.

Slugs do play an important role in the ecosystem of the garden however when their population numbers get too high they do shift as they have in my garden to a pest.

Using mulch and making compost in the garden does provide a food source that can allow the population to boom like it has this year.  I however will continue to use the methods as the benefits far outweigh the increase in slug populations.

General Pest Management Philosophy

My general philosophy for managing pests in my garden is to establish an ecosystem that will allow for self-regulation of pests by predators.  Using store bought pesticides such as slug baits are effective however may have unintended consequences that can make things worse.

As I said earlier slugs do have a role to play in the garden breaking down organic material and fungi releasing nutrients into the soil for the plants.  If you complexly eliminate them you may be knocking out an important food source for the predators that under normal conditions keep their populations under control.  Once the predator population drops slug population spikes can become much more frequent as that natural control is just not there.

So with this in mind I am going to take a look at other ways I can manage this year’s slug outbreak.

Passive Slug Management

The first consideration for managing any pests is passive methods. As I just mentioned slug predators usually keep their populations under control.  As such I try to make my garden an habitat that can support the predators.  I do this by planting a wild variety of crops in high density essentially creating a little eco system.

By planting a Polyculture I have created a habitat that can support a wide variety of animals including slugs and their predators.  This establishes a self-correcting population that reduce the chance any pest will be able spike in population numbers sufficiently to cause damage.

The second benefit of a Polyculture is that pests have a harder time finding the crops they prefer and when they do there is not enough of any one crop to feed a subsequent population boom further compounding the problem.

Active pest management

As in nature from time to time populations will boom and much like this year I will have to spring into action to manage the problem until the ecosystem can get control of them and re-establish equilibrium.

I have been focusing my efforts on the areas where I have seen damage.  The intent is to manage the slugs just long enough for my plants to take off and their predators to get them under control.

Do Eggshells Deter Slugs?

I started with probably the most common advice for managing slugs.  I circled the crops that had seen damage with eggshells that were in a variety of sizes from powder to large shards.

The theory being it will be difficult for them to move over.

Turns out the method did not work well in my garden. In fact it seemed to have no effect other than I was able to see the slugs on the white background much easier.

Manually picking and killing slugs

The next stratedgy I implemented was to manually pick the slugs and dispatch them.  Although the eggshells did not stop them from passing it did make it easier for me to see them.  Manual removal is very effective however I am not in my garden overnight which is when slugs are most active.  They can do a lot of damage quickly while I am sleeping often being able to take an untouched seedling and killing it before I wake up in the morning.

So in addition to hand picking them I needed other methods to help support my goals.

Beer Trap

My next strategy was to use a beer trap.

The basic premise is the carbon dioxide being released attracts the slugs and they subsequently drown in the trap. You can use beer however this seemed like a waste of good beer so I used the alternative that on the One Yard Revolution channel.  I added a pinch of brewing yeast to 1 table spoon of sugar and one of flower to water.

Prior to mixing the bait together I prepared the container by cutting slots at the same height in the container leaving a good area below to hold the bait.

I made sure to use a container with a lid so that I can keep the rain from filling the bait area.

In order to install I placed the container in a hole so the soil level was level with the slits I cut into it.  Once settled I poured the bait in and put the lid on.

Slugs are more active during the night so I set up the trap a few hours before dusk allowing the yeast to begin its work.

After a few days the yeast had run out and I over turned the container on the soil and found a number of slugs had fallen into the trap and perished.  You can simply tip the content of the trap onto the garden as the nutrients and yeast can easily be returned to the garden soil.   I refilled it and continued to use it.

Using predators to manage pests like slugs

At this point I had nearly gotten my slug problem under control when mother nature stepped in and gave me a helping hand.  I found a toad had moved into my garden area and the neighbourhood robins have been coming by more often in large numbers.

Toads and robins feed on slugs and can take care of quite a few in a short period of time.  Earlier I had spoken about my pest management philosophy and here they were at work.  The spike in slugs had likely attracted their predators whom were contributing to their control.

Shortly after their arrival I was able to stop hand picking them and using the beer trap.  Mother nature had the problem well under control.

How I will continue

Hand picking, beer traps and predators did work to slow the damage the slugs were causing while eggshells were not effective other than helping me find the slugs to manually remove them. So I thought to myself if I needed to add another slug management method I had better do some research.

Does Salt work to Deter slugs 

Salt is promoted as a method to quickly kill slugs and it is in fact correct.  Dousing a slug in salt is an effective way to draw all of the water from their bodies killing them.  Unfortunately the same method works on plants if that salt gets into the soil.  High concentrations of salt in the rooting zone causes the roots to dry out killing the plant.

Once salt is in the soil it is very hard to get rid of as it does not break down and washing it out would take out all of your plants nutrients as well.

For this reason I will be avoiding the use of salt in my garden entirely.

Does Copper work to deter slugs

Probably the most common recommendation is to use copper as a means to prevent slugs from reaching your plants.

The concept here is the copper acts as a deterrent reducing the slugs ability to move across it.  Should you create an uninterrupted barrier around your plants it is said to keep the slugs out.

Researchers from the University of Newcastle in the UK put this to the test and found that copper foil did have an 80% effectiveness rate as a barrier to slug passage.

For this method to be effective the copper has to be pure and un-corroded. Currency such as pennies may not be made of pure copper and even if they usually have a layer of corrosion on the surface reducing their effectiveness.  Pennies by their round nature also don’t make a very good unbroken barrier.

As such copper foil or strips that can be found at garden centers is the easiest to install.  That said to protect all of the plants in my garden it would likely be pretty costly.

Is Diatomaceous earth effective for slug control

Another method that is promoted as a barrier for slug movement is Diatomaceous earth or DE for short.  DE is essentially made-up of the broken shells of prehistoric diatoms. DE works to aggravate the movement of critters as it is very sharp and cuts them as they move.

DE is very effective at killing insects.  Unfortunately DE does not target pests specifically.  It is active on all insects including beneficial ones such as lady bugs (beetles) and bees.

DE effectiveness as a barrier for slug passage is far less clear.  Studies have shown limited success however constant issues with applying and maintaining an barrier consistently reduced the effectiveness to near zero.[2]  One of the largest issues with effectively applying DE as a barriers is that wind and rain move it quickly reduce the effectiveness usually within a short period of time.


There are many tools available to help you manage slugs in your garden.  No one method is 100% effective however in combination you can successfully manage the issue in your garden.

I prefer to avoid store bough products and rely on a combination of predator control for the most part.  By planting a Polyculture and creating a supportive habitat slug predators are able to control them for the most part.  When the population numbers do spike a combination of manual picking and beer traps has been effective for me until the predators can re-establish equilibrium in my garden habitat.

Products such as slug pellets, copper foil and DE are effective however I would prefer to avoid the expense and unintended consequences these methods can have.

If you would like to see if other projects practices and methods hold up check out the link to the testing garden assumptions series:



[1] effectiveness of copper to deter slug movement

[2] Effects of diatomaceous earth on slugs

About Stephen

The Alberta Urban Garden Channel hopes to promote organic gardening that is simple, sustainable and does not have to cost a lot. We do this by investigating the Science behind gardening, methods, practices and products to make sure that you will have the best chance of successfully growing your own food at home.