Both diatomaceous earth (DE) and silica gel act as a desiccant against pests, inducing a state of dryness on the target insect. In order to adhere to least-toxic pest control, make sure that if you purchase either of these products they are not formulated with a pesticide. A chemical is not necessary for these materials to be effective at pest control. Because they act as a physical insecticide, there is no risk of resistance. Additionally, once applied, these materials are effective almost indefinitely – just don’t get them wet.
Although both of these substances are considered least-toxic by Beyond Pesticides, it is important to note that they are still regulated as pesticides by the U.S Environmental Protection Agency. As with any pesticide, keep these products out of reach of children and only use them in locations where it will not come in contact with people or animals. Use these products with care, as they can cause respiratory irritation if inhaled, and always wear a dust mask and goggles and cover any electronic equipment that could suffer dust damage.
Diatomaceous earth is a soft, naturally occurring rock consisting of fossilized diatoms, a form of ancient algae. It is composed primarily of silicon dioxide, and a very small percent of aluminum and iron oxide. For the safety of you and your family, only purchase food grade DE for pest control. Never apply pool grade DE around your home as it is heat treated so that the silicon dioxide is converted to crystalline silica, a harmful abrasive to the respiratory system that can cause the progressive lung disease silicosis.
While DE works as a desiccant, some also claim that the jagged edges in the microscopic particles that make up DE create cuts on the outside of insects that crawl over it. Whatever the exact mechanism of DE, the material is an effective method of least-toxic pest control.
The wax coatings on insects are no match for the drying power of silica aerogels. Silica gel is actually a hard, solid material that is processed into beads or granules. When pests come into contact with silica gels it causes death by dehydration. Silica gels are non-toxic, but it is advisable to not allow contact with skin. Again, due to its extreme absorption power, keep these products out of the reach of children and pets in order to prevent them from ingesting or inhaling this material.
Desiccating dusts can be blown into voids through small holes drilled into the walls. Dusts placed in wall voids or cracks and sealed can be effective for many years if they are kept dry.They can be used in areas where caulking is not practical, such as in small cracks around doors, cabinets, and molding. They can be used around the edge of or brushed directly into carpets. For pest specific uses of desiccating dusts, refer to Beyond Pesticides Alternatives Page.
For more information on these products, see EPA’s Reregistration Eligibility Decision for the substances