Why does salt kill slugs The short answer

The short answer will be – slugs die from dehydration when salt is poured on them, a body of a slug contains a great deal of water and salt drains that water out of slug’s body when being exposed to it. That’s a horrible way to die if you ask me.

And what about the long answer?

The long answer is – osmosis. Basically, it&

The long answer is – osmosis. Basically, it’s an in detail description of slug’s death when being exposed to salt on its skin and I already feel sorry for a poor creature. Os­mos­is is a nat­ur­al bio­lo­gic­al phe­nomen­on whereby wa­ter passes from one re­gion of high wa­ter con­cen­tra­tion, through a semi per­meable mem­brane to a re­gion of lower wa­ter con­cen­tra­tion. Salt is a desiccant, which means it absorbs water from things.

The skin of the slug is far more permeable than the skin of most other animals. So, salt on its skin drys water pretty quickly from it. And there the process of osmosis starts. The water from other parts of the slug’s body rush to restore what’s lost and the poor slug rapidly loses more fluid than it can tolerate, and quickly dies from dehydration.

This process won’t happen on humans and most of the animals whose skin is more impermeable and contains less percentage of water in the body, but something similar would happen to plants. Which is good to know in case we get attacked by an army of plants from outer space 😉

Does Salt Deter Slugs?

Many people assume that salt can be used to deter slugs. However, this is not always the case. Salt is used mainly to kill slugs, but it is only effective in the short term.

Firstly, you require a lot of salt to kill one slug, and if you have a large infestation, using salt will not solve the problem. You need to use salt directly on each individual slug so sprinkling 10, 20 or 30 slugs with salt is not an efficient way to deal with them.

S Slugs

A way you can, however, use salt to deter slugs is to create a barrier. You can have the salt barrier around the base of plants that are particularly impacted by slugs. Simply sprinkle a solid line of salt around the base of the plant.

Unfortunately, this is also not the most effective deterrent against slugs as a little wind or rain will wash the barrier away and you’ll have to repeat the process over and over again.

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Why does salt kill slugs?

Throwing salt on a slug is one way of killing them. But why do slugs dry out and die when exposed to salt? The slugs die because of a process called osmosis, which occurs when a solution meets a permeable membrane.

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As you’re likely aware, slugs are pretty moist, sticky, slimy, water-filled creatures. The cells of its skin are extremely permeable, so when you sprinkle salt on a slug, it easily mixes in with the water that the slug continuously secretes.

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As the salt and water mix to create salt water, the slug will secrete even more water from its body in an attempt to dilute the salt water solution covering its body. If you use enough salt, the slug will secrete too much water and die of dehydration. This is why salt kills slugs.

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Read More: Ants In The Garden? Here’s What To Do

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How Can I Get Rid of Slugs?

  Ant Dust - While “ant” is in the nam
  • Ant Dust – While “ant” is in the name of TERRO® Ant Dust, this product is highly effective at eradicating a slug population. Just sprinkle the dust around the perimeter of the area you want to protect and it will start working as soon as a slug passes over the dust. For additional protection, sprinkle the Ant Dust in areas where slugs congregate to stay moist, including cracks in sidewalks, under boards and rocks, in leaf piles and so on.
  • Multi-Purpose Insect Bait or Perimeter Ant Bait Plus – Two other TERRO® products, Multi-Purpose Insect Bait and Perimeter Ant Bait Plus, should be used at the beginning of the season and every four weeks after. By broadcasting these granules in and around your ornamental plants, you will have your slug problem under control in no time.
  • Beer – Making a ‘Slug Pub’ is a moderately effective way to get rid of slugs. Start by sinking a small, but deep, bowl so its lip is flush with the ground and then filling it with beer. Slugs are attracted to the smell of yeast and come to feed. As we said, this method is only moderately successful as some of the slugs, but probably not even half of them, will slide into the beer and drown.
  • Ducks – Ducks are one of the few domesticated animals that eat slugs, so if you can make your yard duck friendly, you may be able to get your slug population under control. Of course, you’ll need to train those ducks to not eat your plants.
  • Slug hunts – Visit your garden or lawn at night and, armed with a flashlight, bucket and old fork, go on a slug hunt. Scoop up any slugs you see and deposit them in a bucket where they will drown in a soap-and-water solution.

What makes salt deadly?

Gardening 101: Salt is a gastropod’s kryptonite and prevents these slimy crawlers from damaging plants. Snail and slugs have a foot composed of cells, which can be thought of as bags of organelles inside an aqueous medium surrounded by a cell membrane. The cell membrane is a semi-permeable phospholipid bilayer. The semi-permeability allows for the selective passage of molecules. Thus, smaller molecules can pass through with ease, while larger ones are prevented from crossing the membrane. Osmosis can occur due to the presence of the semi-permeable membrane. Osmosis is a process in which solvent molecules migrate from a solution of lower concentration to a higher one through a semi-permeable membrane. The difference in concentration on the two sides of the membrane leads to the build-up of osmotic pressure. This pressure is responsible for the movement of the solvent molecules. 

Movement of solvent (water) across a semi-permeable membrane (Photo Credit : Nasky/Shutterstock)

Now, animal cells are not composed of water alone. They also contain several ions, including Na+ and Cl-, which form common salt. When salt is sprinkled on them, the salt crystals bind to the moisture on their skin. This creates a highly concentrated NaCl solution, leading to the development of osmotic pressure. A solution with high salt concentration is called a hypertonic solution. When a hypertonic solution surrounds animal cells, they tend to shrivel up due to heavy water loss. Water rapidly travels out of the cell to dilute the salt solution outside. The movement of water molecules ceases when the salt concentration on either side of the membrane is equal. This is how aquatic snails and slugs survive in saltwater. They have an equal amount of salt in their cells as the water around them possesses!

Effect of salt concentration of the surrounding medium on animal cells (Photo Credit : Naeblys/Shutterstock)

Now, coming back to the unfortunate land dwellers. Water loss triggers the production of a slimy secretion to prevent the skin from drying up. Bubbling occurs as air is driven out of the critter’s body while it shrivels up. Enough salt can cause the slimy being to die fairly easily from dehydration. As you can expect, this is incredibly painful. 

Bubbling of slime as the air tries to escape from  the skin (Photo Credit : Rita Piermiakova/Shutterstock)

Could Salt Still Work?

There are also positive reports that salt can help fight slugs and snails without unintended side-effects.

Salt desert.
Salt desert.

To achieve this, double-sided tape is applied around flower tubs and carefully sprinkled with fine salt crystals.

This solution should successfully fend off slugs and snails, without becoming ineffective with the first rain.

I have yet to try this. I worry that rain or watering could quickly wash the salt into the ground.

But maybe slug collars could help prevent this from happening.

So, my tip is to treat this idea with caution. However, it can be tested easily and is cheap, too.

If you have any experiences with this solution, I would be glad to read about them below.

Salt belongs into the kitchen – not into the
Salt belongs into the kitchen – not into the garden.

Are There Different Kinds of Slugs?

There are dozens of slugs native to North America

There are dozens of slugs native to North America as well as several invasive species that have established a firm footing here. These are just a few of those species:

  • California Banana Slug – This slug is often bright yellow with black spots, giving it the appearance of an old banana.
  • Carolina Mantleslug – Covered in a mottle of black speckles, this slug has a head to tail mantle.
  • Changeable Mantleslug – This slug has a light brown body with brown flecks.
  • Dusky Slug – A small, invasive slug from Europe with light brown to yellow coloring.
  • Leopard Slug – Also called the great gray slug, this invasive species has spread throughout the U.S.
  • Pacific Banana Slug – Found along the Pacific Coast , this slug can reach nearly 10 inches long.
  • Reticulate Taildropper – A slug with an internal shell that has a light brown to red body.
  • Scarletback Taildropper – A slug with a red back and gray sides that grows to be about 2 inches long.
  • Striped Greenhouse Slug – An invasive slug with a light brown body that measures only a few inches when grown.
  • Three-banded Garden Slug – An import from Europe, this slug has three thin dark bands running lengthwise on its body.
  • Winding Mantleslug – A small slug, less than an inch long, with flecks of dark brown.
  • Yellow-bordered Taildropper – A large slug with a bright yellow border around its mantle area.

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