Phosphite-induced suppression of Pseudomonas bleeding canker (Pseudomonas syringae pv. aesculi) of horse chestnut (Aesculus hippocastanum L.)

Abstract

Field trials were conducted using 4-year-old horse chestnut (Aesculus hippocastanum L.) to assess the efficacy of potassium and silicon phosphite as plant protection agents against the bacterial pathogen Pseudomonas syringae pv. aesculi (Pae) the causal agent of Pseudomonas bleeding canker of horse chestnut. Phosphites were applied preventatively, i.e. before Pae inoculation of trees, and curatively, i.e. after Pae inoculation of trees, and, as both a foliar spray (FS) and root drench (RD). Application of both phosphite forms induced positive effects on plant vitality (increased leaf chlorophyll content, leaf chlorophyll fluorescence (F_v/F_m)), enhanced defensive enzyme activity (β-1,3-glucanase, peroxidase) and reduced Pae lesion size, the main proxy of Pae success or aggressiveness. Preventative rather than curative phosphite application resulted in greater reductions in Pae severity. Little significance of mode of application (FS, RD) and phosphite anion (potassium, silicon) was demonstrated indicating both phosphites can be foliar applied or root drenched with similar degrees of resulting Pae control. Significant reductions in Pae severity recorded in this study gave credence to the potential of phosphites as an alternative or compliment to conventional bactericides for Pae control.

Keywords::

• systemic-induced resistance
• integrated disease management
• bacterial bleeding canker
• urban trees

Additional information

Notes on contributors

Glynn C. Percival

Dr Glynn Percival is the plant physiologist and technical support specialist for the F.A. Bartlett Tree Expert Company Ltd and manages their UK research and diagnostic laboratory based at the University of Reading in the UK. He has an active research and training programme at the Laboratory and University that focuses on many different aspect of tree care. Recent studies have included work on tree survival following transplanting, novel methods of pest and disease control and the effects of environmental stress on tree physiology. He has been invited to present papers on his work at the International Society of Arboriculture and Arboricultural Association annual conferences and in addition the International Society for Horticultural Science, First International Symposium on Urban Tree Health. He is the author of over 100 scientific papers, magazine articles and book chapters. In addition, Dr Percival is on the editorial board for Arboriculture and Urban Forestry and Urban Forestry Urban Greening. Reading University made him an honorary visiting research fellow, citing his valuable contributions within the Plant Science Department and the University. He is also a visiting lecturer at Kew Gardens.

Jonathan M. Banks

Jon Banks is the plant diagnostician and research technician for the F.A. Bartlett Tree Expert Company Ltd. He has been involved in Bartlett research at the University of Reading since 2010. He was awarded the Gatsby Summer Bursary for his research on plant stress mitigation and the R F Addey Memorial Prize for Horticulture while studying for his undergraduate degree at the University of Reading. He is currently undertaking PhD studies concerned with drought tolerance within the Acer genus and in addition informs Bartlett representatives of recent developments in pest and disease diagnostics and management.