Phosphite use in turfgrass, the full story

Queen's Suite 3
9:30AM - 12:45PM, 20 Jan 2026

Phosphite has been used in the turfgrass industry for many years, this class will explain exactly what it is, provide a description of its formulation, history of its usage from the early 1980’s to the present. Does phosphite provide a source of phosphorus nutrition? John will show published research answering this and its effect on turfgrass growth and development. Disease suppression by phosphite is a major factor in its use, the results of field trials confirming its ability to not only suppress turfgrass pathogens but also to enhance turfgrass quality will be shown and discussed. John will then explain the means of suppression, providing the results of in vitro laboratory work determining the fungistatic properties of phosphite and how phosphite stimulates and enhances turfgrass defence responses, again from our published peer reviewed papers.  

Learning outcomes 

  • Understand what phosphite is chemically and its effects on turfgrass growth and development 
  • Understand that phosphite can suppress some turfgrass pathogens and enhance turfgrass quality 
  • Understand how phosphite is taken into the turfgrass, how it translocates, how long it remains in the plant and how it stimulates a defence response in the turfgrass. 
  • Learn the detrimental effect phosphite can have in low phosphorus situations 

Presented by:

John Dempsey.png 1
Dr John Dempsey

Chief Scientist Independent Turfgrass Research

Dr John Dempsey is a turfgrass scientist specialising in plant pathology. His career began in the 1980s with greenkeeping, culminating in his role as Superintendent of The Royal Curragh, Ireland’s oldest golf course, from 1993 to 2019. John's educational journey spans from basic greenkeeping courses at the botanic gardens in Dublin to a 1st Class Honours Degree in Turfgrass Science from Myerscough College in the UK, and a PhD in Plant Pathology from the University of the West of England, Bristol, completed in 2016. For the past 15 years, John has conducted independent research on turfgrass disease management, nutrition, and surfactants, publishing numerous articles on infection processes and turf health. He has presented the results of his research at numerous conferences and seminars in Ireland, UK, France, Germany, Norway, Sweden, Czech Republic, USA, Canada, Iceland, Japan and at the GCSAA Conference and BTME in the UK.

 

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