DIATOMACEOUS EARTH

WHAT IS IT?

Diatomaceous earth is obtained from deposits of diatomite, fossilised sedimentary layers of tiny phytoplankton called diatoms, many of them originating at least 20 million years ago in the lakes and seas. These small creatures have survived with few major changes until today. Two major types exist, marine and freshwater. Diatoms are all single-celled organisms, actually small plants, that photosynthesize, producing much of the world's oxygen.
MODE OF ACTION
Diatomaceous earth is a form of amorphous silica that can kill insects by desiccation, by absorbing the oily or waxy outer cuticle layer by direct contact. When the thin, waterproof layer is lost, the insect loses water and dies. In addition to its desiccant action, it works abrasively to rupture insect cuticles. Some insects are more vulnerable due to their anatomy and physiology. Those with large surface area to volume ratios (often smaller insects) are more susceptible.
POSSIBLE USES
STORED GRAIN
Diatomaceous earth has great potential as a grain protectant. It is non-toxic, provides good protection when grain is stored properly, can be easily separated from the grain, by washing, and can possibly be recycled in storage bins. Toxicity is so low that DE is not counted as a foreign substance when grain is rated by the United States Department of Agriculture.
Important factors to be considered when using diatomaceous earth for grain protection are: the amount used, type of grain, particular pest problems, moisture levels in the grain, relative humidity, temperature, and length of storage. DE is not as effective on corn or sorghum, as it does not adhere well to the grains.
When moisture content of the grain is low eg 9.25% and large concentrations of DE (3500 ppm) are used, stored products are protected better with DE than with a standard malathion treatment, with almost complete protection from insect damage for 12 months.
GARDEN USE
Very few controlled studies of diatomaceous earth use in gardens and farms have been conducted. DE may be effective in controlling aphids, red spider mites, oriental fruit moths, snails, slugs and codling moths. The major problem with outside use, other than possible toxicity to beneficial insects, is the nuisance value of the dust. The dust always needs to be reapplied after rain. It is extremely fine and does not adhere well to foliage unless applied when the plants are slightly moistened or with an electrostatic applicator.
As a snail barrier, a 6 cm wide band, 5 mm thick is spread around the area to be protected. A dust mask and protective clothing should be worn when dust is applied.
DE can also be used as a spray, 1 part DE to 5 parts water and a dash of soap, and applied to trees.
DE is less effective in hot, humid weather. Control is better in areas of low rainfall.
To minimise death of beneficial insects, diatomaceous earth should be applied late in the afternoon or at night. Some parasitoid wasps that control pests will be adversely affected by the dust, even more than the insect pests. Excessive application rates contribute to greater losses of beneficial insects.
SEED STORAGE
Diatomaceous earth can be added in small quantities to stored vegetable seed to protect it from pests.
HOME USE
In the home, diatomaceous earth can be applied in wall voids, behind cupboards and refrigerators to kill insects such as ants. It can be sprinkled on carpets to kill fleas, and on shelves to control silverfish.
It is also effective as a cockroach control, killing the cockroaches by abrading their outer coverings, allowing metabolic sap to leak out, causing them to dehydrate and die. As they lose body moisture, roaches become frantic in their search for water. This may make them more visible for a week or so after the dust is applied, but within 2 to 3 weeks most of the cockroaches should be dead. Because diatomaceous earth is inorganic and non-volatile, it can remain active for years if kept dry.
PETS
Diatomaceous earth can be used as a non-toxic control for fleas on dogs and cats.
A small hand duster can be used to apply 30 g of DE for cats and smaller dogs and 60 g for larger dogs. Apply the dust around the ears, avoiding the face, over the back, around the tail, legs, abdomen and between the toes. One dusting is sufficient to treat cats and short-haired dogs. Long-haired dogs may need two treatments.
The dust is more effective if the dog is bathed and combed first. Severely matted hair should be clipped before the dust is applied. Keeping the animals on a leash for several hours allows time for all fleas to contact the dust before the dust is partially removed through the normal activities of the animal. The dust should remain on the animal for as long as possible, at least a week, before bathing is resumed.
After treating the pet, apply diatomaceous earth to the areas where the pet sleeps or roams. Thoroughly powder all sides of the pet's bedding, including baskets or boxes where the pet sleeps. DE can also be applied to lawn areas without damage. An average size backyard can usually be treated with 300 g of dust.
FARM ANIMALS
Dairy farms sometimes feed their animals food containing 1 to 2% DE to control worms and other internal parasites. Added to a dustbath in small quantities (100g:2m2), diatomaceous earth will help to control lice and mites on poultry. Dusting the poultry to control lice would need to be done with care to avoid eyes and inhalation of the dust. A heavy application of DE dust to cattle can control cattle lice.
TOXICITY
Ingestion of diatomaceous earth is not toxic to mammals, but care should be taken to avoid getting the dust into your lungs or eyes. Protect yourself with goggles and a face mask. The only possible health effect comes from long term chronic exposure to quantities of the inhaled dust. It is important that only natural diatomaceous earth be used for insect control not DE treated for swimming pool filter use, as this contains crystalline silica, a dangerous respiratory hazard.