Electrostatic application of a plant-disease biocontrol agent for prevention of fungal infection through the stigmatic surfaces of blueberry flowers

The long-term application of chemical pesticides for protecting agricultural crops has helped ensure increased food and fiber yields for the world's growing population, but not without certain disadvantages such as environmental impact and eventual development of pest resistance. Biologically derived pest-control agents offer significant promise as alternatives to chemical pesticides but may require precision delivery onto specific plant structures. This paper investigates the incorporation of electrostatic force to increase the mass transfer of the viable bacterial biocontrol agent Bacillus subtilis onto stigmatic surfaces of blueberry flowers for protection against a flower-infecting fungal pathogen. The population density of 1.52×105 colony-forming units (CFU) of biocontrol agent electrostatically deposited per ∼0.7-mm-diameter stigma exceeded by 4.5-fold that deposited by conventional hydraulic spraying. Stated differently, one-eighth to one-quarter rate electrostatic-spray applications deposited at least as many CFU as did conventional full-rate application of B. subtilis. These deposition results, as well as measurements of stigma-style charge relaxation (τ=44ns), portent well for efficacious plant disease protection by electrostatic spraying of this bacterial biocontrol agent.