Which type of pesticide formulation looks like dust but does not dissolve in water?

The formulation that resembles dust but does not dissolve in water is typically a type of pesticide known as a "granule." Granules are solid pesticide formulations that are often used for soil application or as a broadcast treatment. They are designed to be spread onto the surface of the ground or mixed into the soil, and they release their active ingredients slowly over time, as moisture is absorbed. Unlike dust formulations that may dissolve in water, granules maintain their physical form and are not meant to be mixed with water for application.

In comparison, the other options represent different characteristics. Wettables usually form a suspension in water when mixed, soluble formulations are designed to dissolve completely in water, and microencapsulated products contain active ingredients enclosed in a coating that allows gradual release, which is different from simply looking like dust. Therefore, granules are the correct choice for a formulation that appears as a dust but does not dissolve in water.