Efficacy of sterilants to kill Erwinia amylovora

Abstract

Fire blight, caused by Erwinia amylovora, can be spread through orchards and nurseries because of poor sanitation practices such as contaminated secateurs. This research investigated the efficacy of 12 commercial sterilants at varying concentrations to kill E. amylovora on secateurs. Secateurs were dipped into an Erwinia amylovora inoculum solution (10⁶ colony forming units/mL), and then misted with a test sterilant. After 10 s, secateurs were swabbed and plated onto Kings B agar plate, incubated at 26 °C for 48 h and bacterial colonies counted. Sterilants were also assessed for cotton bleaching and metal corrosion. Best performing sterilants were then tested as described above by cutting through infected plant material containing sticky bacterial ooze as inoculum. Each of the sterilants tested (methylated spirits (95% and 70%), sodium hypochlorite (NaOCl) (1%, 0.5%, 0.135%), Bac-Stop/benzalkonium chloride (2%, 1%), Virkon™ (label rate), Dettol (50%, 10%, 1%, 0.1%), and HarvestCide® gel (0.1%, 0.5%, 1%)) were found to be effective to kill E. amylovora on inoculum-coated secateurs. The best performing sterilants (methylated spirits, Dettol, HarvestCide gel, NaOCl) were also effective in killing E. amylovora on infected plant material when compared with the untreated control. Most sterilants, except methylated spirits or Dettol, caused corrosion of metal and bleaching of cotton. Each of the tested sterilants were found to be effective to kill Erwinia amylovora on inoculum-coated secateurs and inoculum in plant material and bacterial ooze. Many of the best performing sterilants were likely to damage tools over time and cause bleaching on clothing. However, Dettol or methylated spirits did not cause metal corrosion or bleaching.