European Journal of Plant Pathology

, Volume 134, Issue 2, pp 357–365 | Cite as

Inactivation of Phytophthora and bacterial species in water by a potential energy-saving heat treatment

  • W. HaoEmail author
  • M. O. Ahonsi
  • B. A. Vinatzer
  • C. Hong


Plant pathogens, especially Phytophthora and bacterial species, in re-circulated irrigation water present a significant health risk to nursery and greenhouse crops. Heat treatment at 95°C for 30 s is one of the most reliable technologies for irrigation water decontamination. The primary objective here was to examine whether the water temperature required to inactivate major pathogens in re-circulated irrigation water can be lowered from 95°C to conserve energy and improve horticultural profitability while reducing environmental footprint. Specifically, we investigated the effect of water temperature on Phytophthora nicotianae zoospore survival in the laboratory and on annual vinca under greenhouse conditions. We also assessed the effect of water temperature on survival of chlamydospores of P. nicotianae, oospores of P. pini, six plant pathogenic bacterial species and Escherichia coli. The zoospores of P. nicotianae did not survive and cause any disease on annual vinca when exposed to 42°C for 12 h or 48°C for 6 h. No chlamydospores of P. nicotianae survived 42°C for 24 h or 48°C for 6 h, nor did the oospores of P. pini at 42°C for 12 h or 48°C for 6 h. In addition, none of the seven bacterial species survived 48°C for 24 h. These results indicate that the required water temperature to eliminate Phytophthora and bacterial species may be lowered substantially from 95°C by longer exposure time, improving the economics and environmental footprint, without sacrificing efficacy of heat treatment.


Chlamydospore Nursery and greenhouse crops Oospore Re-circulated irrigation water Zoospore 



This work is partly supported by the Fred C. Gloeckner Foundation, Inc and a grant from the USDA National Institute of Food and Agriculture - Specialty Crop Research Initiative (Agreement #: 2010-51181-21140). We would like to thank Dr. Anton Baudoin, Dr. Erik Stromberg, and Dr. Michael Benson for their valuable advices on this study, and we also would like to thank Patricia Richardson, Xiao Yang, and Lauren Achtemeier for assisting with the greenhouse experiments.


  1. Ahonsi, M. O., Banko, T. J., & Hong, C. X. (2007). A simple in-vitro 'wet-plate' method for mass production of Phytophthora nicotianae zoospores and factors influencing zoospore production. Journal of Microbiological Methods, 70, 557–560.CrossRefPubMedGoogle Scholar
  2. Ann, P. J., & Ko, W. H. (1988). Induction of oospore germination of Phytophthora parasitica. Phytopathology, 78(3), 335–338.CrossRefGoogle Scholar
  3. Baker, K. F., & Matkin, O. A. (1978). Dectection and control of pathogens in water. Ornamentals Northwest, Apr-May, 12–13.Google Scholar
  4. Bollen, G. J. (1985). Lethal temperatures of soil fungi. In C. A. Parker, A. D. Rovira, K. J. Moore, & P. T. W. Wong (Eds.), Ecology and management of soilborne plant pathogens (pp. 191–193). St Paul: American Phytopathological Society.Google Scholar
  5. Bush, E. A., Hong, C. X., & Stromberg, E. L. (2003). Fluctuations of Phytophthora and Pythium spp. in components of a recycling irrigation system. Plant Disease, 87(12), 1500–1506.CrossRefGoogle Scholar
  6. Cayanan, D. F., Dixon, M., Zheng, Y. B., & Llewellyn, J. (2009). Response of container-grown nursery plants to chlorine used to disinfest irrigation water. Hortscience, 44(1), 164–167.Google Scholar
  7. Erwin, D. C., & Ribeiro, O. K. (1996). Phytophthora diseases worldwide. St. Paul: APS.Google Scholar
  8. Evans, R. D. (1994). Control of microorganisms in flowing nutrient solutions. In R. D. MacElroy, C. A. Mitchell, M. Andre, et al. (Eds.), Life sciences and space research Xxv vol 14. Advances in space research (pp. 367–375). Oxford: Pergamon.Google Scholar
  9. Gallegly, M. E., & Hong, C. X. (2008). Phytophthora: identifying species by morphology and DNA fingerprints. St. Paul, MN, USA: APS Press.Google Scholar
  10. Gallo, L., Siverio, F., & Rodriguez-Perez, A. M. (2007). Thermal sensitivity of Phytophthora cinnamomi and long-term effectiveness of soil solarisation to control avocado root rot. Annals of Applied Biology, 150(1), 65–73.CrossRefGoogle Scholar
  11. Hong, C. X., & Moorman, G. W. (2005). Plant pathogens in irrigation water: challenges and opportunities. Critical Reviews in Plant Sciences, 24(3), 189–208.CrossRefGoogle Scholar
  12. Hong, C. X., Richardson, P. A., Kong, P., & Bush, E. A. (2003). Efficacy of chlorine on multiple species of Phytophthora in recycled nursery irrigation water. Plant Disease, 87(10), 1183–1189.CrossRefGoogle Scholar
  13. McPherson, G. M., Harriman, M. R., & Pattison, D. (1995). The potential for spread of root diseases in recirculating hydroponic systems and their control with disinfection. Mededelingen Faculteit Landbouwkundige en Toegepaste Biologische Wetenschappen Universiteit Gent, 60(2b), 371–379.Google Scholar
  14. MEPS and Labelling Requirements. (2005). Equipment Energy Efficiency Program of Australian, State and Territory and New Zealand Governments. Retrieved April 2, 2012, from
  15. Munnecke, D. E., Wilbur, W., & Darley, E. F. (1976). Effect of heating or drying on Armillaria mellea or Trichoderma viride and relation to survival of Armillaria mellea in soil. Phytopathology, 66(11), 1363–1368.CrossRefGoogle Scholar
  16. Pettitt, T. R., Finlay, A. R., Scott, M. A., & Davies, E. M. (1998). Development of a system simulating commercial production conditions for assessing the potential spread of Phytophthora cryptogea root rot of hardy nursery stock in recirculating irrigation water. Annals of Applied Biology, 132, 61–75.CrossRefGoogle Scholar
  17. Runia, W. T., & Amsing, J. J. (2001). Disinfection of recirculation water from closed cultivation systems by heat treatment. Acta Horticulturae, 548, 215–222.Google Scholar
  18. Runia, W. T., Vanos, E. A., & Bollen, G. J. (1988). Disinfection of drainwater from soilless cultures by heat-treatment Netherlands Journal of Agricultural Science, 36(3), 231–238.Google Scholar
  19. Smith, J. H. (1923). The killing of Botrytis cinerea by heat, with a note on the determination of temperature coefficients. Annals of Applied Biology, 10, 335–347.CrossRefGoogle Scholar
  20. Stanghellini, M. E., Kim, D. H., Rasmussen, S. L., & Rorabaugh, P. A. (1996). Control of root rot of peppers caused by Phytophthora capsici with a nonionic surfactant. Plant Disease, 80(10), 1113–1116.CrossRefGoogle Scholar
  21. Stanghellini, M. E., Rasmussen, S. L., Kim, D. H., & Rorabaugh, P. A. (1996). Efficacy of nonionic surfactants in the control of zoospore spread of Pythium aphanidermatum in a recirculating hydroponic system. Plant Disease, 80(4), 422–428.CrossRefGoogle Scholar
  22. Thomson, S. V., & Allen, R. M. (1974). Occurrence of Phytophthora species and other potential plant pathogens in recycled irrigation water. Plant Disease Reporter, 58, 945–949.Google Scholar
  23. Tsao, P. H. (1971). Chlamydospore formation in sporangium-free liquid cultures of Phytophothora parasitica. Phytopathology, 61, 1412–1413.CrossRefGoogle Scholar
  24. van Kuik, A. J. (1992). Spread of Phytophthora cinnamomi Rands in a recycling system. Mededelingen Faculteit Landbouwkundige en Toegepaste Biologische Wetenschappen Universiteit Gent, 57, 139–143.Google Scholar

Copyright information

© KNPV 2012

Authors and Affiliations

  • W. Hao
    • 1
    • 3
    Email author
  • M. O. Ahonsi
    • 1
    • 2
  • B. A. Vinatzer
    • 3
  • C. Hong
    • 1
    • 3
  1. 1.Hampton Roads Agricultural Research and Extension CenterVirginia TechVirginia BeachUSA
  2. 2.Energy Biosciences Institute, Institute for Genomic BiologyUniversity of IllinoisUrbanaUSA
  3. 3.Department of Plant Pathology, Physiology, and Weed ScienceVirginia TechBlacksburgUSA

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