Although diatomaceous earth falls into the nontoxic category of insect repellents, and is in fact allowed as a treatment in organic farming, the product still requires some caution when you apply it. With the proper application, it can be foolproof in killing a number of destructive pests that can eat your vegetable crops overnight.

How It Works

When insects crawl over soil treated with diatomaceous earth, they get tiny cuts from the sharp edges of the substance. The bugs then die from dehydration as their body fluids leak out. Diatomaceous earth also absorbs fats from the outer layers of the bugs' skins or exoskeletons, also causing dehydration.

The Right Type of Diatomaceous Earth

Natural diatomaceous earth comes from crumbled sedimentary rock that contains the fossilized bones of organisms called phytoplankton. Although it is not toxic to humans, dogs or cats, the product can cause irritation or damage to lungs and nasal passages if it's inhaled. Another kind of diatomaceous earth that is used in swimming pool filters contains crystals of silica and can cause severe damage to people and pets, so avoid that type completely in your garden.

When to Use Diatomaceous Earth

Diatomaceous earth is most effective when the soil or area where you spread it is dry. Wet soil or rain will dissipate the powder and allow it to soak into the soil rather than sitting on the top of the soil where insects will run into it. Apply the powder during a dry day, and reapply it after a rainfall or a heavy dew.

Tip Diatomaceous earth kills many different insects, including ants, aphids, centipedes, cutworms, crickets, Japanese beetles, millipedes, slugs, snails, sow bugs and squashbugs.

How to Apply

You have options for how to use diatomaceous earth, depending on the bugs you want to target:

Squeeze a puff of the powder into crevices in the walls, steps or walkways around your vegetable garden where some bugs might be hiding.



Spread the powder around the base of plants to target cutworms, Japanese beetles, slugs, snails, squashbugs and other bugs that you can't see during the daytime.

Sprinkle the powder anywhere on the soil where insects will encounter it, such as entrances to garden beds or the sides of paths.

Sprinkle the powder onto the leaves and stems of plants plagued by insects.

Apply a puff of diatomaceous directly on bugs as you see them. Use enough of the powder to coat them completely and heavily.