How does insecticide get on insects?

Atmospheric drift and surface or systemic contact are ways by which insecticide gets on insects. Atmospheric drift describes the movement of granules and particles -- beyond the target -- in breezes and winds. Surface contact references to the brushing of insects against granules in soil or particles on foliage whereas systemic contact refers to the ingestion of particles while the insect in question feeds upon a plant's internal, life-sustaining liquids.