Electrostatic Pesticide Spraying: Concepts and Practice

The system requirements and characteristics necessary for the design and development of electrostatic-spraying machines uniquely adapted to agricultural pesticide applications are presented. The fundamental approach utilizes an electrostatic-induction nozzle to atomize pneumatically the spray (e.g., 30-50 μm volume median diameter (VMD)) and to charge the conductive liquid (e.g., 10
^-1
-10
⁴
Ωm) typically to a -10-mC/kg. charge-to-mass level. Aerodynamic trajection then disperses the charged pesticide droplets deep into the electrostatically shielded plant canopies where the electric field of the interspersed cloud's space charge (e.g., -20 μC/m3) is mainly relied upon for deposition. While the transient charge- transfer capability of living plants has been experimentally verified as adequate for electrostatic, spraying, gaseous discharges between sharp leaf tips and incoming charged spray clouds have been shown to introduce a deposit-limiting condition which is dependent upon plant morphology. Mass-transfer studies of the agricultural electrostatic spraying system have documented increases in droplet deposition efficiency ranging from two- to seven-fold onto various model and biological targets as compar, d with similar, uncharged sprays and with, conventionally applied sprays. Field evaluations of full-scale prototype electrostatic pesticide-spraying machines have verified the insect-control efficacy of electrostatic applications of 1/2-rates of pesticide to be equal to conventional spray application requiring full rates.