Evaluating options to increase the efficacy of biocontrol agents for the management of Pantoea spp. under field conditions

• Published in: Plant disease
• Main Authors: Koirala, Santosh, Myers, Brendon, Shin, Gi Yoon, Gitaitis, Ron, Kvitko, Brian, Dutta, Bhabesh
• Format: Journal Article
• Language: English
• Published: United States 01.09.2023
• Subjects: disease development and spread; Vegetables; cultural and biological practices; Prokaryotes; Crop Type; Causal Agent; Disease management; Epidemiology; Subject Areas
• ISSN: 0191-2917
• DOI: 10.1094/PDIS-11-22-2710-RE

Center rot of onion is caused by plant pathogenic Pantoea species which can lead to significant yield losses in the field and during storage. Conventional growers use foliar protectants such as a mixture of copper bactericides and an ethylene-bis-dithiocarbamate (EBDC) fungicide to manage the disease; however, organic growers have limited management options besides copper-protectants. Biocontrol agents (BCAs) provide an alternative; however, their efficacy could be compromised due in part to their inability to colonize the foliage. We hypothesized that pre-treatment with peroxide (OxiDate 2.0: a.i. hydrogen peroxide and peroxyacetic acid) enhances the colonizing ability of the subsequently applied BCAs leading to effective center rot management. Field trials were conducted in 2020 and 2021 to assess the efficacy of peroxide, BCAs (Serenade ASO: Bacillus subtilis and BlightBan: Pseudomonas fluorescens) and an insecticide program (tank mix of spinosad and neem oil) to manage center rot. We observed no significant difference in foliar AUDPC between the peroxide pre-treated P. fluorescens plots and only-P. fluorescens treated plots in 2020 and 2021. Peroxide pre-treatment before B. subtilis significantly reduced the foliar AUDPC as compared to stand-alone B. subtilis treatment in 2020; however, no such difference was observed in 2021. Similarly, peroxide pre-treatment before either of the BCAs did not seem to reduce the incidence of bulb rot as compared to the stand-alone BCAs treatment in any of the trials. Additionally, our foliar microbiome study showed comparatively higher P. fluorescens retention on peroxide pre-treated onion foliage; however, at the end of the growing season, P. fluorescens was drastically reduced and was virtually non-existent (<0.002% of the total reads). Overall, the pre-treatment with peroxide had a limited effect in improving the foliar colonizing ability of BCAs and consequently a limited effect in managing center rot.