Wettable Powders

Pesticides formulations: Dusts (D)

Pesticides formulations: Dusts (D)

A pesticide formulation is a combination of active and inert ingredients that forms an end-use pesticide product. Pesticides are formulated to make them safer or easier to use. This is because many pesticide active ingredients, in “pure” (technical grade) form, are not suitable for application. In their concentrated form, some are extremely toxic, many do not mix well with water, some are unstable, and some are difficult (or unsafe) to handle, transport, or store. To address these problems, manufacturers add inert ingredients to end-use pesticide products. Inert ingredients have no pesticidal activity, and some simply serve as diluents or carriers.

Dusts (D)

Most dust formulations are ready-to-use and contain a low percentage of active ingredient (usually 10% or less by weight). A few dust formulations, however, are concentrates and contain a much higher percentage of active ingredient. These concentrates must be mixed with dry inert carriers before application.

Dusts have one or more active ingredients plus a very fine, dry inert carrier made from talc, chalk, clay, nut hulls, or volcanic ash. The size of individual dust particles varies, but all are quite small. Due to their small size, dusts need careful handling to prevent non-target exposure, including drift. They are not water-soluble. Therefore, do not mix them with a liquid solvent.

Dusts are always used dry. They are often used as seed treatments and in some other agricultural operations. Some ornamental and garden pest management products aimed at homeowners are dust formulations. In structures, dust formulations are useful to treat cracks and crevices and for spot treatments to control insect pests. Dusts are also a good tool to control lice, fleas, and other external parasites on pets and livestock.

Special dusts known as tracking powders are effective for insect and rodent monitoring and control. These products are finely ground dusts with an adsorbed stomach poison. Insects and rodents walk through the dust, pick it up on their legs and bodies or feet and fur, and ingest the poisonous dust when grooming. Tracking powders are effective in sites and situations where bait acceptance is poor (for example, where food is abundant).

NOTE: Another option is to use a nontoxic powder, such as talc or flour, to monitor and track rodent activity in buildings


  • Usually ready-to-use; no mixing.
  • A good alternative where moisture from a spray might cause damage.
  • Applied with simple application equipment.
  • Effective in hard-to-reach indoor areas.


  • Easily drift off target during application.
  • Residues do not adhere to treated surfaces, including foliage, as well as liquids do; may easily wash off or blow away.
  • May irritate eyes, nose, throat, and skin; pose a relatively high inhalation exposure risk to handlers.
  • Dampness may cause product to clump and equipment to clog; difficult to apply in damp or humid environments.
  • Some kinds of application equipment and devices are hard to calibrate.
  • Difficult to get an even distribution of particles.

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