Spots or streaks show that the material was poorly mixed. Improperly blended or mixed dusts will not spread the toxicant evenly on the treated surface. If the dust is unusually gritty, the material was not ground sufficiently. This also could cause uneven distribution of the formulated material to plants or other treated surfaces. This type of formulation would be very abrasive in a duster.
Lumpy dusts are due to faulty formulation or improper storage.
In either case, the material would not flow through a duster properly. Granular formulations are primarily soil treatments and may be applied either directly to the soil or over plants. When applied over plants, the granules fall through the foliage to the soil. Some granules are applied to water either directly or over foliage. Since the granules do not adhere to the foliage of most plants, phytotoxicity and residue problems are reduced.