Once the need for an insecticide is confirmed, it should be applied as efficiently as possible. In the middle of hot, dry days, insects are less active and less likely to come in contact with the insecticide. It will also be difficult to get good coverage of wilted plants, and heat will volatilize some insecticides before they reach the plant. Using the most appropriate sprayer will also increase efficiency as only chemicals deposited on plant surfaces kill insects. For aphids and other underleaf insects, only spray deposited on leaf undersides is effective.
Conventional sprayers rely on gravity and inertia to deliver pesticides.
By some estimates, only half the pesticide applied adheres to the plant. Electrostatic sprayers which apply an electrical charge to the material being sprayed reduce spraying time and improve insect and disease control per unit of chemical applied. The charged chemical is attracted to the opposite electric charge on the leaf surface so that retention is better. To further increase efficiency, the charged spray can be delivered with a turbulent air blast, carrying the material deeper into the plant canopy. Higher amounts of sprays from air-assisted electrostatic units were also found deeper in the crop canopy compared to the amounts delivered by uncharged hydraulic sprayers.