We hear the letters “DE” being discussed at the feed store, in garden clubs, and in the online forums where many of us are members. But what exactly are the uses of this so-called “wonder powder,” and why should every gardener keep some on hand? Keep reading and I’ll tell you why it deserves a place in every kitchen and every barn!
What is Diatomaceous Earth?
DE is short for diatomaceous earth. It’s not really a type of soil, despite the name. It is actually the fossilized remains of diatoms, a type of hard-shelled algae. Some species are still alive in our lakes and oceans today, but most of the deposits mined over the past hundred and fifty years are ancient layers of soft sedimentary rock from the Tertiary or Quaternary period. Deposits reach 90 feet thick in places in Europe, and an astonishing 1000 feet thick in parts of Nevada in the US. These deposits can also be found at the surface in the Sahara Desert, and mixed with volcanic ash deposits all over the Northern Hemisphere. It’s this volcanic ash layer mixed in that gives DE its high silica content. From 1837-1914 almost all the mining of DE was from the region around Luneberg Heath in northern Germany, where it was initially discovered and thought to be limestone.
When DE was first discovered by a man digging a well, he assumed it was just a common limestone deposit and he wanted to use it as an agricultural fertilizer. But further research revealed that it wasn’t limestone at all and it had other interesting properties. In the 1860s, Alfred Nobel used it in the manufacture of dynamite to help make nitroglycerin more stable. And Wilhelm Berkefeld used it successfully as a filter during the 1890s – his method later went into production and was used to filter drinking water during a cholera epidemic. Since that time, the main uses for various types of DE have included being used a filtering agent in brewing, filtering liquids and syrups (DE doesn’t alter their color or flavor), filtering water in swimming pools and fish ponds, and in scientific labs where little coffin-like tubes of DE are used as a no-clog filter to trap very fine particles. Other uses over time have taken advantage of its very fine abrasive nature – it has been used in toothpaste, facial scrubs, and metal polish. But I’m not so worried about making metal polish today, so let’s talk about how DE can help you around your home and out in the garden.
Diatomaceous earth is approved and regulated by the FDA. It comes in 2 primary forms, the kind used for filtration, and food grade – which is the one we’re interested in. DE is considered to be 100% natural. Of course, there are lots of things that are “natural” that are deadly poisons, but food grade DE is safe to eat and it has a myriad of uses for homesteaders. The main use of DE on our own homestead is as an insecticide, and we also use it in our food storage. I can already hear you now… “Gasp! Elizabeth uses an insecticide? I thought she was organic?!” Well calm down for a second, and let’s discuss this a little bit…
How Diatomaceous Earth Works
An insecticide is anything that kills insects. Technically that makes my boot an insecticide every time I pick a cucumber beetle off my potatoes and stomp on it. I know that we associate the word “insecticide” with deadly chemical sprays, but in this case it’s not a chemical poison but rather a purely physical process. It’s like the boot stomp, but on a much larger scale. The abrasive properties of DE are well documented. If you look at DE under a microscope, you will see that its particles are covered in tiny spikes and sharp corners. It is this abrasiveness that kills bugs like fleas and beetles, and even slugs. You might ask, “How does it do that?” Well, first of all let me clarify that we are talking about food grade DE – not the swimming pool filtration variety. The swimming pool variety has been heat treated and does not work as well for this purpose. The food grade powder works to absorb fats and wax from the outer shells and skins of insects. Without these waterproof protective coatings, the insects become vulnerable. The sharp surfaces of the DE particles can now scratch and cut the insect’s body, and the insects die a slow death of dehydration as their insides bleed out. The waxy exoskeleton of a beetle, for example, keeps their innards moist; when the wax layer is removed and then the shell gets scratched, he beetle will dehydrate and die. It’s not an instant process but the powder will stay on your plants until it is washed or blown off, so it remains effective over long periods of time, especially in dry weather or in a greenhouse or other indoor environment.
DE has many potential uses as an insecticide against bed bugs, fleas, lice, ticks, mites, weevils, aphids, and a whole host of other insects. It is less effective on slugs than I would like, and we do not use slug pellets, so I typically use a bait board to attract the slimy critters. What is a bait board? I use several old fence boards that are 1″ x 6″ and 6 feet long, but you could use anything you’ve got handy. I imagine that pallet wood would work well for this use too. My boards are half rotten at this point, and they have definitely seen better days, but they still work great for pests from earwigs (for which I have a particular disliking) to the lovely, slimy, slug. I simply walk out to the garden first thing in the morning before I feed my poultry, and I turn all the boards over, exposing the critters below. The ducks and chickens have learned what I’m up to when I do this, and they come out for a pre-breakfast snack. The chickens love anything that moves except slugs, and the ducks gulp down the slugs without a second thought. In fact, I’ve seen the ducks go out into the garden at night specifically looking for slugs and other creatures that emerge from their hiding places when the coolness of the evening lures them out to feed. That’s a great reason to keep a few ducks out near your garden.
Uses for DE in the Garden
A dusting of food grade DE will take care of most pests on your plants, both indoors and out. From the tiniest aphids and spider mites on your roses and house plants, to the largest beetles on your squash, DE kills them all. It’s not instant, but within a few days you’ll see a definite improvement. It doesn’t matter how you apply the dust, but if you’re shaking or blowing it on dry, then it’s recommended that you use a dust mask and goggles. The particles that will dry out your bugs will definitely dry out your nasal passages and eyes too, so avoid breathing it in and try to dust on a day that’s not windy – I think that’s pretty obvious. I can make enough mess in the garden without getting myself and everything else covered in dust, so here at Humblebee Farm we apply our DE in a solution. I guess technically it’s a suspension because it doesn’t dissolve – but either way we make a liquid spray. One drop of liquid dish soap can be used to break the surface tension of the water if you like, and then I fill a sprayer with a half cup of DE, topped up the rest of the way with a gallon of water. This gallon of mix will usually do a good coating on a 200 foot row of potatoes, and it goes further on less dense plants. If I have a bad infestation of beetles I will make the mix stronger initially by using a gallon of water to 3 cups of DE powder. The best way to judge the amount needed is to see if it’s working and reapply as needed until you see a drop in the number of adults. Insects can develop a resistance to chemicals over time, but DE is a physical treatment and they can’t become resistant to it. When you spray the plants, do try to get the underside of the leaves (the powder will last longest under there) as well as the tops. A good even coating is best, and this can be reapplied every week if it’s still needed. If you’re having a problem with beetles, I recommend spraying the soil immediately under the stalks of the plants too. Be aware that creating a thick white layer on the tops of the leaves is also going to block the process of photosynthesis that feeds the plant, and could potentially lower fruit quality if the leaves are left covered in DE for long periods of time. Another drawback to using DE as a spray is that the particles can have a tendency to clog your sprayer nozzle. I sometimes mix in a powdered fish fertilizer at the same time to give the plants a boost, and it could be that the combination is what really clogs my nozzle. The better the nozzle that you’ve got, the less likely it is to clog up in the first place. Make sure you know how to remove and clean out the tip of your want or nozzle, and carry a pin with you for poking out the holes if they do become clogged. It’s so frustrating to have to stop what you’re doing and trek all the way back to the house for what amounts to a 15 second fix. It’s inevitable that it’s going to clog sometime, so just take a little squeeze bottle of water and a pin for cleaning out the tip and you’ll be glad you did. If you have a backpack style sprayer then just use a safety pin or diaper pin and secure it directly through one of the straps, then it’s always right there when you need it.
What about those pesky ants in your lawn? I think we have probably all heard about using powdered sugar mixed with borax to kill ants, and it works. You can also sprinkle DE over trails, over the nest, and over any access holes you can find to kill the pesky little critters. I’m an organic farmer so I respect the natural world and realize that there is a balance in nature. But we humans have done so much to disrupt that balance that sometimes things get out of control. I’d like to think that’s why mosquitoes and ants are here – to remind me that I’m not in control of nature, but that I’m simply one piece in a massive, beautiful puzzle. But just because I don’t understand their purpose in this world and find them incredibly annoying doesn’t mean that they all deserve to die. I do know that mosquitoes play a role in pollinating wild grasses but I’m still okay with wearing bug repellent to deprive the biting insects of a meal, and emptying all containers after it rains to eliminate breeding places. I will also kill ants if they’re being bothersome inside the house or if they have built a large nest in a common walk way. I don’t want to see my kids get bitten, and I will quite happily sprinkle DE over the ants’ homes until they die or move to a more appropriate location on the farm. Trust me, in this sandy loam soil of ours, there’s no shortage of ants.
What about the bees and pollinators? Won’t DE affect them too? Sadly, yes it can, so you should only use DE on your plants if you really need to and not as a preventative. It’s not a poison that the bees will carry back to the nest, poisoning the other bees, but regardless you should use it with common sense and only when necessary. When we spray we try to do it in the evening when the bees have returned home, and we try spray before flowers have formed or just try not to get any spray on the flowers. Since most of the pests we are trying to kill are eating the leaves, we concentrate on those. The bees, of course, are interested only in the flowers and they don’t typically come into contact with the leaves much.
Uses for DE in the Coop
Anyone who has kept chickens and turkeys knows that they love to have a dust bath! It’s a natural way of cleaning themselves and removing external parasites such as lice and mites. Our flock have made all sorts of hollows in the ground to use as dust baths – under cars, sheds, and their special little spots in the garden. If left to range I know your birds will do the same and you can help them out by adding some DE to the soil in an existing bath. The chickens will coat themselves and do a good even job, much better than you or I could ever do. If you have your birds in a run, I have a great idea that’s easy to use, easy to clean, and makes use of recycled tires… the tire bath. Take an old tire (the larger the better) and place it in a sheltered spot so that it stays as dry as possible. Shade is also nice for the birds who will often be seen flopped over the side of our tire bath, having a nap like it’s a hot tub. Fill your tire half way up with dry peat moss, just the regular garden kind, and then add 4 cups of DE before gently mixing it all together. Don’t worry if it isn’t perfect, the chickens will finish mixing it all up for you. Now just wait for them to discover their new bath and you’re away to the races! It’s inevitable that they’ll kick out some of the mix, and remove more in their feathers, and this is what we want. So you can top up your dust bath by adding a bucket of peat moss with 2 cups of DE mixed in whenever the level is looking a bit low. To keep it dry in wet weather, you can throw a piece of plywood over the top of the whole thing and remove it again when the weather clears. DE is also good inside the coop. You can dust your walls and perches with it to kill mites and mix some right into the litter on your floor. I know that many poultry keepers recommend adding DE to the feed, and while there’s still no conclusive proof that it works, there also hasn’t been enough proof to say that it doesn’t work. If you want to add it, I say go right ahead. It’s already present in some feeds as an insecticide and anti-caking agent.
Uses for DE in the Pantry
As well as being used in livestock feed, DE is used in grain storage for humans and animals alike. It’s approved by the FDA and is used in the storage of grains, legumes, rice, corn, and other dry foods. If you’re storing your own food you can certainly add the appropriate type and amount to increase the quality of stored grains by protecting them from insect infestation. De also helps to keep grains dry, which protects against clumping and mold. The recommended amounts are 1-2 cups of food grade DE to every 50 lbs of stored grain. 1 cup for short term storage (under 2 years) and 2 cups for longer storage. You just mix it in as evenly as possible and then close up your storage containers. It’s that simple. DE doesn’t interact with oxygen remover packs, so you can use both methods if you like – although DE is more readily available and doesn’t require any special packaging except to be kept dry. Keeping your DE in a closed container in the kitchen or barn, where it’s away from moisture, will ensure that you have a good supply ready when you need it.
Food grade DE is usually a white or off-white color, and it is readily available at gardening and hardware stores, health food stores, and greenhouse suppliers. But given the many uses for DE and the fact that I’d like to save you money, I highly recommend that you visit a local feed store and buy a large bag. We’ve found that there is only a few dollars difference between buying a 4 liter jug of the powder and buying a whole sack. I remember that a few years ago it was actually a dollar cheaper for the large sack than the pretty little bottle on the shelf. As long as you’re getting the food grade and not the filter grade, then you’re good. The filter grade has different particle sizes and the heat treatment it is subjected to changes the chemical composition. The typical DE that you’ll use around the garden is made up of 80-90% silica and varying amounts of calcium, iron oxide, and aluminum from clay soil. The soil composition varies significantly, depending on the age of the deposit and its underlying geology, but for our purposes they will all work.
Uses for DE in the Barn
Like the coop, you can use DE mixed with bedding, or apply it around the walls and crevices, to keep down all manner of insects. You can also use it as an insecticidal dust on your animals directly, but avoid applying it to their faces where they might breathe it in. Dusting along the topline and under the legs of your livestock will help kill any fleas, lice, and ticks. And we’ve had good results on our dog too. If you live in a heavily infested area you may have to combine your use of DE with another product, but having another tool in your toolbox is always good, isn’t it? DE is safe to use on young animals with the same precaution that you try to avoid breathing it in. Once it’s been applied it will quickly absorb moisture and oil from the coat and skin and become less dusty, so it’s only the initial application that causes any problems. Any excess dust will quickly settle onto the bedding and stay there. Do your research and see if you think DE is a good addition to your barn hygiene.
Is Diatomaceous Earth Right for You?
That’s a decision you’ll have to make for yourself. Talk to trusted friends and the feed store operators and you’ll be amazed how many people use it. Do some reading and research about the benefits of DE in your animals or livestock, and out in your garden, and then go from there. If you like the idea, ask a friend for some DE to test with and give it a try yourself. You can always pay them back later when you buy your own bag.
Have you used DE before? Do you have other uses or great ideas that you’d like to share? We’d love to hear from you in the comments below. Learning from each other and sharing ideas is one of the great things about a place like this. As always, have fun in the garden!