Eggshells control slugs, according to most books, and all kinds of gardening experts. Slugs and snails can be a real problem in the garden, eating all those precious plants. It seems to be a constant battle and eggshells are routinely recommended.
Do they really work?
The theory is as follows. Broken eggshells have sharp edges, and if slugs crawl on them, they will get cuts on their bellies, and die. So they are smart enough to stay off the eggshells.
Testing Eggshells to Control Slugs
A website called Allaboutslugs.com has tested eggshells in a great little experiment. The following information and pictures are taken from their site, with permission. For full details on the experiment go to Eggshell Myth: good idea or all cracked up?
Eggshells were crushed, and left outside for two weeks so that the rain could wash away anything that might attract slugs. Two pieces of lettuce were used as tasty bait, and one was surrounded with eggshells. Slugs were added.
Both pieces of lettuce were partially eaten, and slugs seemed to have no problem crawling over the eggshells. Even after 8 hours, the slugs were still having a good feast and did not seem to be suffering very much from all of the ‘cuts’ they got the night before.
Eggshells, Beer and Slugs
We know from How To Get Rid of Slugs With Beer, that slugs are attracted to beer – or at least yeast. Will they cross eggshells to get to beer? Here is a great video.
Do Eggshells Control Slugs?
The first experiment done by Allaboutslugs (not reported here) had the slugs going to the eggshells first – they preferred them over the lettuce. Both of their experiments showed quite clearly that eggshells do not stop slugs.
The beer, slug and eggshell video shows the same thing. Slugs were crawling all over the eggshells and did not seem to mind.
Granted, this is just 2 experiments, with 2 0r 3 types of slugs. There are many types of slugs and snails and it is possible other types react differently to eggshells.
Without further experimental evidence to the contrary, I have to conclude that eggshells do not keep slugs away from plants.
Does Egg Shell Size Matter?
One of my readers commented that the egg shell pieces in the above were quite large. A common suggestion is to break the shells into very small pieces. The theory here is that small pieces are sharper – or at least there would be more sharp edges. Would small pieces be harder for the slug to crawl over?
I could not find a good video with smaller pieces of egg shell, but I did find this video. I think it clearly shows that sharp objects don’t deter slugs or snails.