Diatomaceous earth

Definition

A soft, porous, siliceous sedimentary rock composed primarily of fossilized diatom frustules, processed into a fine abrasive powder. The microscopic silica particles abrade the cuticular waxes and cause desiccation in soft-bodied arthropods, making it a mechanical insecticide and acaricide used in stored-product protection, greenhouse management, and domestic pest control.

Etymology

From diatom (microscopic silica-walled algae) + -aceous (resembling) + earth (soil or mineral matter); coined to describe the geological origin of the material.

Example

Grain storage facilities dust wheat with food-grade diatomaceous earth to suppress populations of the lesser grain borer (Rhyzopertha dominica) and flour beetles (Tribolium spp.) without chemical residues.

Synonyms

• diatomite
• kieselguhr
• kieselgur

Related Terms

• cuticular wax
• desiccation
• mechanical insecticide
• stored-product entomology
• silica aerogel
• inert dust

Usage Notes

Food-grade diatomaceous earth is required for applications near human food or animal feed; filter-grade or pool-grade products are calcined and crystallized, posing inhalation hazards. Efficacy depends on ambient humidity—high moisture reduces desiccant action. Not effective against arthropods with heavily sclerotized cuticles or those inhabiting moist microhabitats.