Rock Dust: Can Tiny Stones Stop Slugs and Snails?

Some people suggest using rock dust/rock flour to build little walls around plants.

These walls should protect them against slugs and snails.

Does Rock Dust / Powder / Minerals / Flour Work Against Slugs?

This method is based on the fact that snails dislike crawling over dry materials.

Therefore, slugs will also avoid rock dust.

The theory is that they lose a lot of mucus and moisture by crawling over rough and dry surfaces.

As rock powder is particularly rough and dry, it should repel slugs and snails.

If snails lose too much water, they become inactive and move back to shady and moist places to balance their fluid.


experiment test
This is the theory; does it work in practice?

Rock Dust Against Snails: Practical Test

Since it is not known whether rock dust has a deterrent effect, I developed a test.

I laid out a semicircle of rock dust and put about 20 slugs and snails in the middle.

What happened then is shown in the following video.

Video: Rock Dust Against Slugs and Snails

The result was inconclusive.

The test demonstrated that the dry rock powder deterred some tiny slugs.

Unfortunately, the rock dust was unable to stop the larger slugs.

Therefore, this method can be used in spring when most slugs are still small to provide at least a little safety to the plants.

The method cannot guarantee secure protection and needs to be combined with other measures.

In the long run, it will help to attract natural predators of snails to the garden.

In the short term, barriers against slugs and snails can provide additional protection.

Rock Dust Products

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How is Rock Powder Applied?

The application is simple and self-explanatory.

You pour a broad wall around the plants and beds that you would like to protect.

This barrier should be at least 812 inches (2030 cm) wide to have a repellent effect.

Sometimes, sprinkling whole plants with the mineral powder is also recommended so that it becomes more difficult for slugs and snails to move over the leaves.

However, this might harm the plants and reduce their ability to use photosynthesis.

Therefore, handle the dust with caution and do not overuse it.

This method could be used at night. Then you could rinse off the dust in the morning.

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advantages strengths of this slug control

Advantages of This Method

In addition to its effect on slugs, rock dust has other positive qualities.

As it is rich in minerals, it improves the health and quality of soil.

It not only loosens the soil, but also provides useful nutrients and trace elements, such as potassium and phosphorus.

Overfertilization with rock dust is not possible, which simplifies handling.

Undesirable side effects do not occur.

Furthermore, the mineral powders help in binding moisture in the soil. This helps to prevent dehydration during a drought.

Furthermore, the pH value of the soil can be regulated, as depending on its ingredients, rock dust can be slightly acidic as well as alkaline.

Usually, it is alkaline and therefore can contribute to increasing the pH value of acidic soils.

Another positive effect is its use against unwanted odors.

Therefore, in compost, it not only helps to speed up the composting, but also helps to suppress unpleasant odors.

This feature can also be useful if you work with liquid manures, as they tend to smell unpleasant.

Disadvantages weaknesses of this slug controlDisadvantages of Rock Flour

Unfortunately, this measure is no miracle cure for slug and snail infestations.

Bigger slugs that cause most of the damage cannot be deterred.

Therefore, its use to control slugs is only partially successful.

Furthermore, this rock dust does not work to deter slugs when it gets wet, e.g., after irrigation or rainfall.

Therefore, it becomes ineffective at times when slugs and snails are particularly active.

It therefore requires continuous maintenance, which requires time and money.

Furthermore, if you inhale the dust, it can cause respiratory problems.

Therefore, the rock powder should be spread only in calm weather, and you need to use a mask.

plus minusConclusion

Rock dust is not very effective against slugs and snails; it only deters some of them when it is very dry.

Nevertheless, since rock flour has many positive effects, its use is recommended.

There are no adverse side effects, and the application is simple.

If you take care not to inhale the dust, no harm can occur.

Unfortunately, it is not cheap if you would like to use it a lot.

This method has the significant disadvantage that it loses its deterrent effect in damp circumstances.

Therefore, rock dust is only advisable for use with other more efficient and sustainable slug control measures.


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Price and Products

Rock dust is available in different compositions.

Its price is relatively low, and you can buy it in every garden market.

Depending on the quantity and type, prices vary from 25 cents to around 2 $/₤/ per pound.

Although rock dust is not sufficient to control against slugs, I recommend using it in the garden for the abovementioned reasons.

Limestone Rock Dust Products

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Alternative Slug and Snail Barriers

Mechanical barriers are suitable alternatives to barriers formed by mulch materials.

They are also efficient and require no further work once constructed.

Although slug fences are not cheap, they are durable and suitable for protecting large beds, and they need no maintenance.

They provide a long-term solution and are less labor-intensive than rock dust and most other methods.

You will find more information here:

 slug collar slug and snail fence test
 Slug barriers: an overview Snail and slug fence test

To protect individual plants, special slug collars can be used.

Also, garden cloches can protect seedlings and young plants.

Furthermore, the anti-slug paint Schnexagon will keep slugs out of beds and greenhouses.

This repelling coating sticks to almost all materials and can be painted on quickly and easily.

Finally, there are other materials that work similarly to rock dust as a deterrent due to their dryness or saltiness.

One possibility, for example, is to use salty sheep wool against snails.

You will find more information here: mulch materials against slugs

Peaceful Slug Control & Plant Protection

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Sheep Wool Pellets | Natural Snail RepellentAnti-Slug Collars | For Single Plants | Multipack
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Mindful consumption: Please only buy what you or your garden really need.

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