Sometimes it is claimed that crushed eggshells can be used as a snail and slug barrier.
But is this only another garden myth, or is there something to it?
In theory crushed eggshells are so sharp that slugs and snails would hurt themselves climbing over them.
Therefore, shells scattered around the plants could become a defensive wall against the snails and slugs.
Critical voices argue that snails and even the feared Spanish slug would crawl over razor blades without any problems.
How should the egg shell be used against snails?
In practice, the empty eggshells are dried and then crumbled into very tiny and sharp-edged pieces, for example, with a rolling pin.
Some people claim, that it is crucial to use only the shells of uncooked eggs. Because cooking them shall decrease the sharpness of the shells.
Others state that the effectiveness depends on the moon.
They recommend that crushing the shells works best with a decreasing moon and the spreading with an increasing moon.
Video: Eggshells idea
Since there was so much discussion on this topic, I felt it was necessary to carry out an experiment.
Therefore I dried and crushed the shells of uncooked eggs.
Then I placed them on a table and formed a little wall, which was around two inches wide (five centimeter) and put some snails and slugs in the middle.
What happened next is shown in the following video:
Video: Eggshells test
Unfortunately the experiment showed that eggshells are not really a safe pest control.
The slugs had no fear of the shells and crawled over them with little hesitation.
On the other hand the snail showed that it does not like to cross the eggshell wall.
It can clearly be observed that it is repelled by the shells.
The same is true for the leopard slug in the beginning.
But after a few attempts, it finally made its way over the barrier a few times.
The final evaluation of this method to control slugs is not clear.
Of course, the ineffectiveness could have been the result of the wrong application.
Maybe the bits were not small enough, or the slugs were left no other way, so they had to take the uncomfortable route over the shells.
Possibly it was also due to the influence of the moon that the results turn out to be poor. Because I did not stick to the recommendations regarding the moon cycle.
Personally I doubt the influence of the moon could make a big difference in this matter.
In the end, I am very skeptical that eggshells are an effective method to protect plants against snails and slugs.
There is eggshell powder on the market, which is sold as a dietary supplement for dogs and could be used.
One good thing about this method is the fact, that if you eat eggs you can get the shells for free.
Also the soil profits from the application of the shells. The included minerals will contribute to the improvement of the soil health.
There are other mulch materials that are supposed to work as snail protection.
A comparison and further tests and information can be found here: mulching material against snails (soon)
Effective Slug Control Alternatives
There are some other slug control methods that might interest you:
slug fences (soon)