Diatomaceous Earth, or DE, is an inert naturally occurring rock like substance that ends up crushed into white powder for further use. DE consists of the remains of fossilized diatoms and generally is composed of 80-90% silica with the remaining portion consisting of clay minerals and iron oxide. The powder is normally used for pool filtration, as an abrasive in toothpaste, an absorbent for liquids, cat litter, reinforcing filler in plastics and as an insecticide.
DE becomes particularly advantageous to the home gardener looking to control garden pests without the use of any potentially harmful chemicals that could get into your produce. DE acts as an abrasive shredding the exoskeletons of hard shelled insects like crickets, beetles, aphids and others causing them to die of dehydration. DE also works well for slugs, performing a similar action of shredding the slug’s body and causing death by dehydration.
One should make sure to only use DE suitable for a garden and not pool DE, as DE made for pools is chemically treated and not necessarily good for your garden let alone an organic garden. Care should be taken to not inhale DE when applying it as it has the potential to cause silicosis, a lung disease. Use of a dust mask or respirator and applying when it is not windy outside is recommended. Alternatively the use of food grade DE has been reported to be associated with silicosis and yet still maintains effective insect killing power.
DE will generally kill any and all insects within your garden. That means both good and bad insects can be killed with its use. In order to minimize the impact on beneficial insects, like pollinating bees, it is recommended that you keep DE away from the flowers of your plants.
I find that by applying DE to my plants when they are small I ensure that insects eating too many young leaves do not stunt their growth. As my garden plants get bigger and better able to handle a few insects nibbling on their leaves, I start to taper off the application of DE unless. If I notice a particularly heavy insect infestation on a mature plant I will sparingly apply DE on the stem close to the ground and around any branches or leaves where the activity is present. I try and leave the flowers DE free. As rain-washes the DE away and dew stops it from working effectively, it will need to be reapplied on an as needed basis.
You may want to try Diatomaceous Earth Food Grade 10 pound bags from Amazon.com. Your local big box hardware store should carry different brands of DE as well. To make the application easier I also use the Pesticide Powder Duster which helps concentrate the DE to the specific areas of the plant I wish to target.