A simple model describes development of early peaks in oomycete zoospore inoculum detected in southern UK outdoors horticultural reservoirs

Tim R. Pettitt, Carsten Ambelas Skjøth


The numbers of water-borne oomycete propagules in outdoor reservoirs used in horticultural nurseries within the UK are investigated in this study. Water samples were recovered from 11 different horticultural nurseries in the southern UK during Jan–May in 2 “cool” years (2010 and 2013; winter temperatures 2.0 and 0.4°C below UK Met Office 30 year winter average, respectively) and 2 “warm” years (2008 and 2012; winter temperatures 1.2 and 0.9°C above UK Met Office 30 year winter average, respectively). Samples were analyzed for total number of oomycete colony forming units (CFU), predominantly members of the families Saprolegniaceae and Pythiaceae, and these were combined to give monthly mean counts. The numbers of CFU were investigated with respect to prevailing climate in the region: mean monthly air temperatures calculated by using daily observations from the nearest climatological station. The investigations show that the number of CFU during spring can be explained by a linear first-order equation and a statistically significant r2 value of 0.66 with the simple relationship: [CFU] = a(TTb) − b, where a is the rate of inoculum development with temperature T, and b is the baseload population at temperatures below Tb. Despite the majority of oomycete CFU detected being non-phytopathogenic members of the Saprolegniaceae, total oomycete CFU counts are still of considerable value as indicators of irrigation water treatment efficacy and cleanliness of storage tanks. The presence/absence of Pythium spp. was also determined for all samples tested, and Pythium CFU were found to be present in the majority, the exceptions all being particularly cold months (January and February 2010, and January 2008). A simple scenario study (+2 deg C) suggests that abundance of water-borne oomycetes during spring could be affected by increased temperatures due to climate change.


Pythiaceae; Saprolegniaceae; populations; seasonal-maxima; temperature

Full Text:



Hong CX, Moorman GW. Plant pathogens in irrigation water: challenges and opportunities. Crit Rev Plant Sci. 2005;24:189–208. http://dx.doi.org/10.1080/07352680591005838

Stewart-Wade SM. Plant pathogens in recycled irrigation water in commercial plant nurseries and greenhouses: their detection and management. Irrigation Science. 2011;29:267–297. http://dx.doi.org/10.1007/s00271-011-0285-1

Hunter PJ, Calvo-Bado LA, Parsons NR, Pettitt TR, Petch GM, Shaw E, et al. Variation in microbial communities colonizing horticultural slow sand filter beds: implications for filter function. Irrigation Science. 2012;31:631–642. http://dx.doi.org/10.1007/s00271-012-0339-z

Büttner C, Bandte M, Pettitt TR. Filtration and centrifugation for detection of plant pathogens in irrigation water. In: Hong CX, Moorman GW, Wohanka W, Büttner C, editors. Biology, detection and management of plant pathogens in irrigation water. Saint Paul, MN: American Phytopathological Society; 2014. p. 139–148.

Werres S, Ghimire SR, Pettitt TR. Baiting assays for detection of Phytophthora species in irrigation water. In: Hong CX, Moorman GW, Wohanka W, Büttner C, editors. Biology, detection and management of plant pathogens in irrigation water. Saint Paul, MN: American Phytopathological Society; 2014. p. 125–138.

MacDonald JD, Ali-Shtayeh MS, Kabashima J, Stites J. Occurrence of Phytophthora species in recirculating nursery irrigation water. Plant Dis. 1994;78:607–611. http://dx.doi.org/10.1094/PD-78-0607

Pettitt TR, Wakeham AJ, Wainwright MF, White JG. Comparison of serological, culture, and bait methods for detection of Pythium and Phytophthora zoospores in water. Plant Pathol. 2002;51:720–727. http://dx.doi.org/10.1046/j.1365-3059.2002.00759.x

Reeser PW, Sutton W, Hansen EM, Remigi P, Adams GC. Phytophthora species in forest streams in Oregon and Alaska. Mycologia. 2011;103:22–35. http://dx.doi.org/10.3852/10-013

Hallett IC, Dick MW. Seasonal and diurnal fluctuations of oomycete propagule numbers in free water of a freshwater lake. J Ecol. 1981;69:671–692. http://dx.doi.org/10.2307/2259691

Skjøth CA, Sommer J, Frederiksen L, Gosewinkel Karlson U. Crop harvest in Denmark and Central Europe contributes to the local load of airborne Alternaria spore concentrations in Copenhagen. Atmos Chem Phys. 2012;12:11107–11123. http://dx.doi.org/10.5194/acp-12-11107-2012

Grewling Ł, Jackowiak B, Nowak M, Uruska A, Smith M. Variations and trends of birch pollen seasons during 15 years (1996–2010) in relation to weather conditions in Poznań (western Poland). Grana. 2012;51:280–292. http://dx.doi.org/10.1080/00173134.2012.700727

Skjøth CA, Bilińska D, Werner M, Malkiewicz M, Adams-Groom B, Kryza M, et al. Footprint areas of pollen from alder (Alnus) and birch (Betula) in the UK (Worcester) and Poland (Wrocław) during 2005–2014. Acta Agrobot. 2015;68(4):315–324. http://dx.doi.org/10.5586/aa.2015.044

Livingstone DM, Lotter AF. The relationship between air and water temperatures in lakes of the Swiss Plateau: a case study with palæolimnological implications. J Paleolimnol. 1998;19:181–198. http://dx.doi.org/10.1023/A:1007904817619

Piccolroaz S, Toffolon M, Majone B. A simple lumped model to convert air temperature into surface water temperature in lakes. Hydrology and Earth System Sciences. 2013;17:3323–3338. http://dx.doi.org/10.5194/hess-17-3323-2013

Thackeray, SJ, Sparks, TH, Frederiksen, M. Trophic level asynchrony in rates of phenological change for marine, freshwater and terrestrial environments. Glob Chang Biol. 2010;16:3304–3313. http://dx.doi.org/10.1111/j.1365-2486.2010.02165.x

DOI: https://doi.org/10.5586/aa.1665

Journal ISSN:
  • 2300-357X (online)
  • 0065-0951 (print; ceased since 2016)
This is an Open Access journal, which distributes its content under the terms of the Creative Commons Attribution License, which permits redistribution, commercial and non-commercial, provided that the content is properly cited.
The journal is a member of the Committee on Publication Ethics (COPE) and aims to follow the COPE’s principles.
The journal publisher is a member of the Open Access Scholarly Publishers Association.
The journal content is indexed in Similarity Check, the Crossref initiative to prevent scholarly and professional plagiarism.
Polish Botanical Society