Diatomaceous earth (DE for short) is the remains of microscopic one-celled plants (phytoplankton) called diatoms that lived in the oceans that once covered the western part of the United States and other parts of the world. Huge deposits were left behind when the water receded. They are now mined and have several important uses in making paint, toothpaste, beer filtering and swimming pool filters. DE is approximately 86 percent silicon, 5 percent sodium, 2 percent iron and many other trace minerals such as titanium, boron, manganese, copper and zirconium.
Diatomaceous earth can be applied in a variety of ways. To use for flea and tick control, apply a light dusting over the lawn, in dog runs, around pet bedding or favorite resting spots. The diatoms grow in freshwater lakes or quiet salt water bays or estuaries, either as individual cells or in long strands that float in the water. They absorb dissolved silica (silicon dioxide) from the water to produce their shells. Almost universally, the source of this silica is volcanic ash which falls into the water and partially dissolves. When the silica is depleted, the diatoms die and their shells fall to the bottom of the lake or bay, building up layers of microscopic fossil shells interbedded with layers of volcanic ash and occasionally with layers of limestone, clay or salt. Another algae bloom develops after the next volcanic eruption, and the process repeats. The resulting deposit is called diatomite (Quarles 1992a; Cummins 1975). Only uncalcined (not heated to high temperatures) DE is suitable for use as an insecticide, as calcining reduces its effectiveness and increases crystalline silica content significantly. Calcined products are typically used for filtration (Quarles 1992a). Since DE is dusty and abrasive, it can cause lung damage if breathed heavily. Remember, however, that breathing any dusty material can be dangerous. Be sure to wear a dust mask if applying with a dry blower. Mixing into a water spray eliminates most of these problems. DE will not hurt earthworms or beneficial soil microorganisms. Diatomaceous earth is one of the few pesticides in the world classified as non-toxic although Iím not real comfortable with that classification. I think anything can be toxic if overused or misused. Fresh water DE that has less than 2% crystalline silica dioxide is the safest and best choice.
DE makes a very effective natural insecticide. The insecticidal quality of DE is due to its absorptive properties. When DE comes in contact with the insects, the powdery DE absorbs the body fluids causing death from dehydration. Said more simply, DE kills insects by drying Ďem up. You will see how drying DE as if you handle it with bare hands.
The best way to apply the dust over a large area is with a light weight apparatus such as Dustiní Mizer, Spritzer or other similar blowers. Applying by hand can be done but wastes a lot of material and will dry your skin. To apply with water, mix ľ cup of DE in a gallon of water and apply to the lawn and/or shrubs where pest problems exist. Itís much more powerful when mixed with pyrethrum.
The wet spray method does work but only after the liquid has dried. Mix from 1-4 tablespoons DE per gallon of water and spray on the lawn, shrubs, tree trunks and building foundations. When the mixture dries, it has the same dehydrating powers as the original dry dust. When sprayed wet the material covers the foliage and other surfaces better than dusting dry, thus giving better insect control. It seems to last longer when applied wet but the dry application is usually more effective at killing insects quickly. DE has no insect killing power while it is wet.
Only pure feed-grade DE should be used to feed animals. There is no residual danger or contamination, in fact, DE is actually beneficial to the soil. Itís loaded with trace minerals. However, there are a few precautions. Diatomaceous earth is very dusty and can cause lung problems if breathed heavily, so when applying it dry always wear a good dust mask or stand up wind. The second precaution is that DE sold for swimming pool filters is ineffective for insect control because it has been heated and chemically treated. Much of the surface area has been removed and itís more dangerous to breath in this form. Finally, DE will kill beneficial insects too, so use it sparingly to kill problem infestations of harmful insects and donít use it too often. Some people would have you believe that DE is untested, unlabeled and therefore unsafe for use. Thatís just one of the feeble arguments left to the organiphobes.
DE has been used for years in the food processing industry to treat stored grains to eliminate weevil and other insect infestations. There are currently dozens of registrations of DE with the EPA for various insecticidal and food supplement uses. DE, with and without pyrethrums and piperonyl butoxide, is registered and labeled for fleas, ants, roaches and many other pests. Piperonyl butoxide (PBO) is a synthetic synergist that is added to increase the killing power of the product. It affects the liver and should never be used. Pyrethrum products in general should be avoided.
For dogs, cats and other pets add enough natural DE to the animals' food to make up 2% of the volume of the food.
Question from Bartlett, TN:
What's the difference between "regular" and "food grade" DE?
(DE Diatomaceous Earth)
A: Swimming pool filter DE is for use in pool filters only. It has been heated and partially melted. Food grade DE is clean and untreated. 05/08