The geometric exoskeletons of the diatoms are made of silicon dioxide.

How Does Diatomaceous Earth Work as an Insecticide?

by Angela Ryczkowski

When insects, slugs or other pests are invading your garden, lawn or house, you may be left searching for a safe, nontoxic pesticide that will effectively curb pest activity. One such material is diatomaceous earth, which is composed of the fossilized skeletons of diatoms, tiny aquatic organisms. Understanding how this material works against pests will allow you to implement it effectively and with confidence around small children, pets and organic gardens.

1. Characteristics of Diatomaceous Earth

Certain physical characteristics of this material are what make it ideal for pest control. Although it appears to be a soft, chalky dust, diatoms have microscopically sharp edges that abrade insects' exoskeletons, leaving them vulnerable to drying out. The diatom shells are also very porous and absorb fats and oils from the outer layer of insect exoskeletons, further encouraging what is essentially a dehydrating of the insects.

2. Pests Controlled

Myriad different pests are controlled by diatomaceous earth. This material is especially effective against soft-bodied pests such as slugs and snails. It can also address problems with ants, fleas, spiders, cockroaches, silverfish and scorpions. In general, diatomaceous earth is best able to control insects and other pests that move primarily by walking or crawling rather than flying. Unlike contact insecticides, it may take a few days for the pest to die following contact with diatomaceous earth.

3. Application Considerations

To protect plants from pests, sprinkle diatomaceous earth around each vulnerable plant or entire plantings as a barrier. On particularly hard-hit plants, you can dust the entire plant with diatomaceous earth. Sprinkle diatomaceous earth completely around structures on the ground next to the foundation to keep out ants and other invading pests. To apply the diatomaceous earth in cracks or crevices, use a bulb duster. High humidity or free water render diatomaceous earth ineffective, so you will have to reapply the material after each rainfall or regularly when conditions are humid.

4. Safety Considerations

Diatomaceous earth is nontoxic, but as a fine dust it can still create problems if inhaled. A small amount inhaled can irritate the nose and throat, while breathing in a large quantity can lead to coughing and shortness of breath. Excessive skin contact may cause irritation and dryness, and diatomaceous earth irritates eyes upon contact. To avoid problems, wear a mask, goggles and gloves to handle and apply diatomaceous earth. Some diatomaceous earth-containing products labeled for pest control may also contain chemicals for increased effectiveness against pests and may be toxic. Pool or filter-grade diatomaceous earth is not safe to use for pest control.

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