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Natural Slug & Snail Controls Tested

Slugs and snails, words to bring fear to any gardener’s heart! It’s been a good year in the endless slug war so far but warm wet weather is ideal for the slimy devils. What to do?

Slugs on Lettuce

Slugs infesting a vegetable garden. 3 on a lettuce!

There are lots of remedies and natural controls advocated for keeping plants safe from slugs and snails but not all of them actually work. Back in 2019 the RHS undertook a study of five popular organic home slug control methods and found them to not be effective.

Slug Ignoring Copper Barrier

Slug Ignoring Copper Barrier

Copper tape, horticultural grit, pine bark mulch, wool pellets and egg shells were all shown to make no difference when applied to lettuce, with gastropods inflicting the same damage to those treated with the remedies as without.

Copper tape is supposed to create a static electricity barrier that the slug won’t cross but as the photo shows, they’re not that bothered by it. Sadly the same goes for the other barrier methods in the list above.

Well the people at Envii make an organic slug control method called Feed & Fortify that uses diatomaceous earth to naturally protect plants from slugs, snails and other small pests. It also contains iron silicates to improve soil fertility and maximise plant growth.
They decided to replicate the RHS study on the slug barriers and also put their Feed & Fortify to the test. The video answers the ‘does it work?’ question (spoiler alert!) – it works.

The feed part of the name – the Iron Silicates – might benefit from a little explanation.

Iron for Plants

Iron is an important micro-nutrient for plants. A sort of plant vitamin. They only need a very small amount, but that small amount is crucial to healthy growth. Iron is utilised in the production of chlorophyll which is the engine that converts carbon dioxide to carbon and oxygen and feeds the plant as well as giving it the green colour.
A lack of iron will show itself as yellowing on the leaves and a sickly plant.

See Chemistry and mineralogy of Fe‐containing oxides and layer silicates in relation to plant available iron

Silicon

Silicon is a common element that aids plant growth and quality, photosynthesis, transpiration and enhances plant resistance to stresses such as drought. (see this article from Greenhouse Management) Plants grown in commercial potting composts – patio pots, hanging baskets etc. – are most likely to be in need of supplemental silicon.

Natural Slug and Snail Controls

Seeing is believing and the film below shows how the slugs react when faced with different barrier methods.

Posted in Allotment Garden Diary
14 comments on “Natural Slug & Snail Controls Tested
  1. Roger Whittaker says:

    I have read somewhere that if you cook with garlic dilute the juices and spray the ground with it this kills slugs and their egg is this true

  2. Marg says:

    Isn’t diatomaceous earth harmful to bees? They have enough problems already.

  3. deborah scollan says:

    We bordered all our raised beds with double bands of serrated copper-tape which is not cheap: then watched during a tea break as the critters just slithered over the two bands. So will give this diatomaceous earth a try. I hear it needs a top-up after every bit of rain? Could be back to the old night patrol with torch and boots! What does work is instant mash potato, the cheapest supermarket kind. Leave dry in little covered saucers with slug access and they go for it big time. I believe they get so thirsty that they then drink big time and the mash swells up and explodes them! I haven’t seen this wonderful spectacle but they do really take the bait and their numbers seemed less.

  4. Peter Clarke says:

    I can’t imagine what the RHS did when they tested copper rings. I’ve used them for years and they work for me, the only thing I can think of is that they failed to put a few slug pellets inside when they put them on. It is possible to trap a slug inside when you set things up and so it will eat your plant. We used the soil association approved pellets.

    • John Harrison says:

      Have you seen the video with the slug happily sliming over the copper band? Or was I stupidly missing a joke? “…they failed to put a few slug pellets inside” 🙂

  5. Peter Clarke says:

    Well the slugs won’t cross the copper rings I use, the pellets put in at the setup prevent and slug that is under the soil inside the ring when you put it in doing any harm there after the ring prevents slugs coming in from outside. They work for me.

  6. Ann T says:

    I am still not sure about this; the Wiki entry mentions dehydration of anything with an exoskeleton and certain types causing silicosis albeit most available now is safer.
    https://en.wikipedia.org/wiki/Diatomaceous_earth

    • John Harrison says:

      Envii have commented on this concern:

      While we do appreciate your concern and whole heartedly agree that we need look out for bees in particular, we do also believe that our product provides a much lower risk alternative to other pest control methods.
      Our recommended method of application is to use the product as a physical barrier and a deterrent rather than to seek to harm insects. As the product is applied on the ground it also shouldn’t impact at all any flying insects who would realistically fly and land on the plant itself.
      This along with the fact that our diatomaceous earth has a more granular and less fine composition than others also means it is less sticky and is much more difficult to cling to insects in the unlikely event that they should come into contact with it. Due to the granular composition of the product, it is also much easier for bees and other flying insects to remove Feed & Fortify by rapidly vibrating their wings.
      While we cannot totally eliminate a very, very small level of risk to insects such as bees the same can be said for bird baths and other common garden features.
      Below I have attached some further information relating to diatomaceous earth and some tips and tricks re: even safer methods of application.
      https://www.diatomaceousearth.com/blogs/learning-center/how-to-apply-diatomaceous-earth-without-hurting-bees
      I hope this goes some way to put your mind at rest.

  7. Simon says:

    I was told to plant garlic and onions around the edges of all the plots to reduce the number of slugs moving in. I don’t think it does, but it is a convenient and sace-saving way of growing the garlic.

    • Vanessa Morrison says:

      We just use dried minced garlic spread like slug pellets. It works exactly the same. Bit smellier but not for long and lasts about the same in similar conditions. Of course you have to buy it in big bags from Ebay or somewhere similar to make it affordable but it works for us.

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