Diatomaceous Earth – what is it? and why use it?

This posts dives into the infamous material known as Diatomaceous Earth (DE). DE was found to have many uses from filtering water and beer to making a “safer” explosive (quotes are for sarcastic purposes). Besides DE’s history, the post will dive into DE’s use and purpose for vermicomposting.


Diatomaceous Earth (DE for short) is basically the fossilized remains of diatoms, a type of algae that lived in lakes, that has been turned into a fine powder. One of the main components of these diatoms is silica. Silica at the microscopic level is quite jagged and sharp which can make DE feel abrasive.

DE was discovered by Peter Kasten around 1836. However, Alfred Nobel would discover that DE could be used to make nitroglycerin more stable which would later be termed dynamite. Yes, that Alfred Nobel, the founder of the Nobel Prize. Here is a link with a more in depth discussion of DE’s origins. Here is the Wikipedia post on DE too.

Another discovery with DE was its ability to filter water from asbestos, algae, and other contaminants. Many pool filters use DE. Just a quick note about this. There are two forms of DE, food grade and filter grade. Food grade is acceptable for use in the garden and worm systems but filter grade is NOT. Here is a post that explains the differences.

Food grade DE was discovered to be an effective pesticide in grain storage. The actual mechanism that kills insects is up for debate. The original theory was that DE’s sharp edges would damage insects’ exoskeleton which would cause them to die or avoid areas with DE. Another theory is that DE causes the insect to “dry out” and terminating them due to a lack of moisture. I should also note that DE primarily works against insects with a hard exoskeleton (ants, bed bugs, cockroaches, fleas) but can also be effective against slugs, snails, and aphids. Here is a post that dives further into DE’s use for pest control.

Before I go any further, I wanted to point out that DE is a very fine powder and can become airborne. Breathing in DE can be EXTREMELY dangerous and can potentially lead to cancer. WebMD has a post on the health risks and potential benefits. I also wanted to point out that there are many “natural health” blogs and videos that make various claims on the benefits of DE. However, there aren’t many scientific studies proving these claims. With any study on health the double-blind study, is considered the gold standard to prevent any biases or placebo effects. My take on it is until it has been proven to be effective and safe, I will simply avoid consuming DE.

DE for Worm Systems

Given the information above, why would DE be used in a worm system? Won’t DE kill the worms since it acts as a pesticide? Is it even safe to use?

First, DE does NOT kill compost worms. Although I couldn’t find any reliable information on this, DE may act as a source of grit for the worms which helps with digestion. However, there are better sources of grit such as crushed eggshells, oyster shell flour, and quarry dust, among others.

Second, is DE safe to use? The short answer is yes. However, due to DE’s ability to become airborne, wear a mask (preferably a N95 or equivalent) and protective eye wear. It may be beneficial to use in a worm system but use caution and don’t harm yourself!

Let’s move on to WHY DE should be used. DE can be effective against a range of nuisance pests in a worm system. I should note that DE doesn’t target specific pests and is more of a general pesticide. DE can help with control over the following pests:

  • Fruit Flies
  • Mites
  • Millipedes
  • Isopods – Roly Polies
  • Ants
  • Cockroaches

Each of these pests may require a different strategy in how to use DE. For example, ants typically don’t live in worm bin but may be attracted by the food scraps. DE can be applied around the bin or around any access point to the bin. This is similar to creating a moat around the bin. This prevents ants from accessing the bin and will eventually move on somewhere else. If there are many ants inside the bin, you can also apply a light layer on the surface of the top layer.

One very important note about using DE. It has to remain dry to be effective. When it is wet, it become ineffective. This is why it is best to add a DRY layer of bedding on top of the composting area and then add the DE. DE should also be applied to the sides of the system.

The most annoying pest (in my opinion) is fruit flies. DE can act as a barrier to fruit flies laying eggs and can dry out the flies. However, fruit flies will often require multiple types of deterrents and elimination methods. Prevention is still the best way to avoid them.

For issues with excessive millipedes, mites, and isopods, DE should be sprinkled on the top surface of the system. This won’t eliminate all of them as they are often found deep in the system, but it can reduce the population. This method will require several applications. I do want to note that millipedes, mites, and isopods are beneficial in worm systems. They assist the worms in breaking hard, fibrous materials down much better than worms. DE should only be used when populations of these insects are outcompeting the worms for food and the worms are adversely affected. This situation is quite rare.

Wrapping up

DE has quite an interesting history in industrial and agricultural applications. Worm systems can benefit from the use of DE to eliminate certain pest insects. However, caution MUST be used in its application. It’s not worth injuring one’s self to save a worm bin! If you want to learn more about DE, there are several links below that you may find interesting:

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