Diatomaceous Earth


Diatomaceous earth is a naturally occurring substance partially comprised of the fossilized remains of diatoms.  Diatoms are microscopic sized hard shelled creatures found in both marine and fresh waters.  The diatom shells are covered in sharp spines that make them dangerous to exoskeletal insects, but not to animals with internal skeletons.  The spines of the diatom skeletons pierce the soft body tissues of insects between their hard exoskeletal plates and it is through these numerous microscopic wounds that the insect loses bodily moisture to the point of desiccating and dying.  Creatures with internal skeletons such as humans, cattle and pets have means of resisting such damage and are not harmed.   Thus, it is possible to mix a small amount of DE into your stored grains and beans to deter insect infestations without having to remove the dust again before you consume them.   Diatomaceous earth works in a purely physical, not chemical,  manner thus has no chemical toxicity.

As neat as this sounds, in the limited number of controlled studies that I have been able to find it seems that DE is not as effective in controlling food storage insects as properly used freezing techniques, fumigation with carbon dioxide (dry ice) or sealing in air-tight containers with oxygen absorbers.  This is primarily for reasons that most of the insects that cause a problem in grain storage are hard-shelled weevils which have only a limited amount of soft tissue exposure.  I now mostly use DE for controlling ants and roaches in areas where I feed my animals and bedding areas.  Still, some folks want to use DE in their food storage so the following information is provided.


IMPORTANT NOTE: There are two kinds of diatomaceous earth to be found on the market and only one of them is suitable for use as an insecticide in your stored grains.  The type you DO NOT WANT FOR FOOD USE is sold by swimming pool suppliers as a filtering agent. DE to be used for filtering has been subjected to a heat treatment that dramatically increases it’s crystalline silicate content which makes it unsuitable for use with your foodstuffs.  The diatomaceous earth that is needed for use in food storage has not been heat treated and has a crystalline silica content of no more than 1-1.5%. It is commonly sold in hardware and garden stores as an “organic pesticide” and is available from a number of storage food dealers.  A few of these suppliers are listed in the Resources section.

I have always purchased my DE from my local hardware store and have had no concerns about its safety.  However, a number of correspondents have reported to me that their local suppliers keep their DE in the same area as their chemical pesticides.  This causes some concern about possible contamination and I no longer recommend using DE from these sources.  Since the actual amount of DE (by weight) that is necessary to protect grains is fairly small I recommend ordering yours from suppliers who will guarantee their product is food grade as stipulated by the US FDA.  This will insure you receive a product that has no deleterious contaminants and is safe to use.

From: higgins10@aol.com (Higgins10)
Originally posted in: rec.gardens

Good afternoon all.  Diatomaceous earth is approved by the USDA as an animal feed additive, however I have found out that there are vast differences between various forms of diatomaceous earth.  Some DE products may not be effective in controlling insects, while others may be harmful to humans and pets.  The most important differences between individual forms of DE is the shape of the diatom, content of Crystalline Silica, and the purity of the Silica Dioxide.  The World Health Organization cautions that DE with a crystalline silica content of three percent or higher is dangerous to humans, (and probably pets and birds as well).  Diatomaceous Earth used in swimming pool filters has close to a 60% crystalline silica content.  I know of a product called Organic Solutions (insecticide) which is approved by both the EPA and USDA and has a crystalline silica content ranging between 0.36% to 1.12% according to its labels etc.  It is classified as Amorphous Fresh Water Diatomaceous Earth (whatever that means).  However, all literature I have read assures it is safe for both humans and animals and seems to be very effective at killing insects.  I stumbled across all this info. while shopping in the mall.  If you’re interested in reading it too, go to the Organic Solutions website at http://www.BuyOrgs.com.  Hope this helps answer the question and always use environmentally safe products! Higgins10

From:  kahless@ns.waymark.net
Date: Sat Aug 24 14:08:48 1996
To: Dunross (A.T. Hagan) Private e-mail

[previous text deleted]

I have always purchased DE at the local feed store.  It’s cheaper there than at the garden and hardware stores.  The feed store I buy at has DE available in bulk, but they’ll package up a smaller amount if that’s what you want.  My package in the garage doesn’t have a brand name but says “Nitron Industries” at the bottom.  The label recommends 7 pounds of DE for each ton of grain.  Ha! As if I had “tons” of grain in storage 8-D

I’ve been using DE for grain storage for about 15 years now but flea control only for the past 6 years.  The only fleas we’ve seen in that period of time is the ones that hitch a ride in with friends pets. A very light dusting afterward takes care of that problem.  Miracle stuff as far as I’m concerned since we’d had an awful time with fleas before we started using DE.  Much much much cheaper and as far as I’m concerned the advantages FAR outweigh the risks.

(hope that was helpful)


To use, you should mix thoroughly one cup (8 fl ozs) of DE to every forty pounds of grain, grain products or legumes.  This works out to approximately one cup of DE to every five gallon bucket of food you want to treat.  You need to make certain that every kernel is coated so it is better to do the mixing in small batches where you can insure more even coating.  Both the grain and the DE should be quite dry when doing the mixing otherwise you’ll get an uneven distribution.

WARNING: DE is a powdery dust which you need to take steps to keep out of your lungs and eyes.  A paint or hardware store filter mask and a pair of goggles will do the job.  It’s a good idea to do the actual mixing outside in a slight breeze otherwise you’ll get DE all over everything.  Even whole wheat flour dust can cause lung irritation if you breathe in a sufficient amount.

Being inactive and usually covered in a hard shell, DE works poorly on insect eggs or pupae.  It has more effectiveness on larvae and adult insects with a fair amount of soft tissue exposure.