Plant Pathogen Dispersal


Plant disease epidemics require plant pathogens to be dispersed to infect new hosts. Understanding dispersal is important for devising methods to improve detection and control of plant pathogens. This is not straightforward, as plant pathogens can be dispersed by air, rain, water or soil, and by vectors such as animals, pollen, various microbes, people and machinery and on infected plant material including seeds. Epidemics vary in time and space as a result of complex processes affecting inoculum availability and production, dispersal and survival processes, and also the coincidence of susceptible crop plants, which each interact with the weather. To reduce disease, exposure of crops to inoculum is often limited by separating crops in time and space, using crop rotation, including different varieties. A wide range of diagnostic methods are increasingly used to help with this by detecting plant pathogens before infection occurs to prevent introduction of exotic inoculum, or to improve applications of crop protection products.

Key Concepts:

  • Plant pathogens include fungi, protists (such as oomycetes and plasmodiophorids), bacteria, phytoplasmas, viruses and viroids. For plant disease epidemics to occur, these plant pathogens must be dispersed to infect new hosts.

  • Plant pathogens can be dispersed by air, rain, water, soil, by animals, people and machinery and through infected plant material including pollen and seeds.

  • A key method for crop protection is to limit dispersal by separating susceptible crops in time and space by crop rotation, use of different varieties, hygiene or management of inoculum and use of crop protection products (biologicals and pesticides) at key growth stages or when infection conditions are suitable.

  • Some pathogens that are dispersed by air are adapted to survive freezing temperatures, high UV light levels and desiccation, whereas others only remain viable for short periods or in certain less extreme conditions. Some may even induce ice nucleation to promote rainfall to return them to the ground.

  • Some plant pathogens are dispersed in rain‐splash, usually short distances but occasionally longer when combined with strong winds. Pathogens can be dispersed in water films and groundwater or rivers.

  • Insects and other invertebrates, pollen and protists may vector some pathogens, mainly viruses, viroids and phytoplasmas.

  • One of the main reasons for new introductions of plant pathogens to a territory is introduction by people, as infected plant material, infected seeds or as contamination on clothing, machinery, food or other imported materials. Various statutory quarantine regulations and inspections by plant health professionals aim to reduce introductions.

  • Climate change may help pathogens to establish in new territories where they were previously absent.

Keywords: epidemics; plant disease; plant pathogens; inoculum; aerobiology; rain‐splash; soilborne; diagnostics; quarantine

Figure 1.

A summary of plant pathogen dispersal processes: soilborne pathogens that are also wind‐blown or vectored, rain‐splash and water, airborne (various spores, cells and biological debris), and vectors (insects (aphids illustrated), fungi (ergots on wheat, which are transported in seed and produce insect‐vectored conidia in ‘honeydew’), pollen (grass and pine pollen shown, which can contain viruses), and people, who are responsible for introductions in imported plants, food and other materials). The centre‐left photo of rain is provided courtesy of Prof. John Lacey (Rothamsted Research).



Anderson PK, Cunningham AA, Patel NG et al. (2004) Emerging infectious diseases of plants: pathogen pollution, climate change and agrotechnology drivers. Trends in Ecology and Evolution 19: 535–544.

Aubertot JN, West JS, Bousset‐Vaslin L et al. (2006) Improved resistance management for durable disease control: a case study of phoma stem canker of oilseed rape (Brassica napus). European Journal of Plant Pathology 114: 91–106.

Barnes CW, Szabo LJ, Johnson JL et al. (2006) Detection of Phakopsora pachyrhizi DNA in rain using qPCR and a portable rain collector. Phytopathology 96(6): S9.

Brown JKM and Hovmøller MS (2002) Aerial dispersal of pathogens on the global and continental scales and its impact on plant disease. Science 297: 537–541.

Chiu ShiauYen, Lu JenYenn, Su YaoChi , Wu YingChang and Chang HsiHsung (2001) The largest biological item on this earth. Asia Seasonly Report of Environmental Microbiology 10(1): 17–20.

Després VR, Huffman JA, Burrows SM et al. (2012) Primary biological aerosol particles in the atmosphere: a review. Tellus Series B: Chemical and Physical Meteorology 64: 15598. doi:10.3402/tellusb.v64i0.15598.

Fernandes FR, de Albuquerque LC, Giordano LDB et al. (2008) Diversity and prevalence of Brazilian bipartite begomovirus species associated to tomatoes. Virus Genes 36: 251–258.

Fitt BDL, Hu BC and Li ZQ et al. (2008) Strategies to prevent spread of Leptosphaeria maculans (phoma stem canker) onto oilseed rape crops in China; costs and benefits. Plant Pathology 57(4): 652–664.

Fitt BDL, McCartney HA and Walklate PJ (1989) Role of rain in the dispersal of pathogen inoculum. Annual Review of Phytopathology 27: 241–270.

Fröhlich‐Nowoisky J, Pickersgill DA, Després VR and Poschl U (2009) High diversity of fungi in air particulate matter. Proceedings of the National Academy of Sciences of the USA 106(31): 12814–12819.

Gottwald TR, Hughes G, Graham JH , Sun X and Riley T (2001) The citrus canker epidemic in Florida: the scientific basis of regulatory eradication policy for an invasive species. Phytopathology 91: 30–34.

Gottwald TR, Sun X, Riley T et al. (2002) Geo‐referenced spatiotemporal analysis of the urban citrus canker epidemic in Florida. Phytopathology 92: 361–377.

Gregory PH (1952) Spore content of the atmosphere near the ground. Nature 170: 475.

Gregory PH (1973) The Microbiology of the Atmosphere, 2nd edn., p. 377. Aylesbury: Leonard Hill.

Harrington R and Stork NE (1995) Insects in a changing environment: 17th Symposium of the Royal Entomological Society, 7–10 September 1993 at Rothamsted Experimental Station, Harpenden, 535 pp. London: Academic Press.

Harvell CD, Mitchell CE, Ward JR et al. (2002) Climate warming and disease risks for terrestrial and marine biota. Science 296: 2158–2162.

Huffman JA, Prenni AJ, DeMott PJ et al. (2013) High concentrations of biological aerosol particles and ice nuclei during and after rain. Atmospheric Chemistry and Physics 13: 6151–6164.

Ingold CT (1971) Fungal Spores: Their Liberation and Dispersal, 302 pp. Oxford: Clarendon Press.

Jackson SL and Bayliss KL (2011) Spore traps need improvement to fulfil plant biosecurity requirements. Plant Pathology 60: 801–810.

Lacey J (1996) Spore dispersal – its role in ecology and disease: the British contribution to fungal aerobiology. Mycological Research 100: 641–660.

Lacey ME and West JS (2006) The Air Spora, 156 pp. Dordrecht, The Netherlands: Springer.

Leyronas C and Nicot PC (2013) Monitoring viable airborne inoculum of Botrytis cinerea in the South‐East of France over 3 years: relation with climatic parameters and the origin of air masses. Aerobiologia 29(2): 291–299.

Lighthart B, Shaffer BT, Marthi B and Ganio LM (1993) Artificial wind‐gust liberation of microbial bioaerosols previously deposited on plants. Aerobiologia 9: 189–196.

Lovell DJ, Parker SR, Van Peteghem P, Webb DA and Welham SJ (2002) Quantification of raindrop kinetic energy for improved prediction of splash‐dispersed pathogens. Phytopathology 92: 497–503.

Macdonald OC and McCartney HA (1987) Calculation of splash droplet trajectories Ag. Forest Meteorology 39(2–3): 95–110.

Marcroft SJ, Van de Wouw AP, Salisbury PA, Potter TD and Howlett BJ (2012) Effect of rotation of canola (Brassica napus) cultivars with different complements of blackleg resistance genes on disease severity. Plant Pathology 61: 934–944.

McCartney HA, Fitt BDL and West JS (2006) Dispersal of foliar fungal plant pathogens: mechanisms, gradients and spatial patterns. In: Cooke BM, Jones DG and Kaye B (eds) The Epidemiology of Plant Diseases, 2nd edn, pp. 159–192. Dordrecht: Springer.

Mims SA and Mims FM (2004) Fungal spores are transported long distances in smoke from biomass fires. Atmospheric Environment 38: 651–655.

Morris CE, Monteil CL and Berge O (2013a) Novel understanding of the water cycle as a link between unsuspected habitats of airborne pathogens – what consequences for plant disease management? Acta Phytopathologica Sinica 43(suppl.): 17. International Congress of Plant Pathology 2013 abstract O01.004.

Morris CE, Sands DC, Glaux C et al. (2013b) Urediospores of rust fungi are ice nucleation active at >−10 °C and harbor ice nucleation active bacteria. Atmospheric Chemistry and Physics 13: 4223–4233.

Pady SM and Kapica L (1955) Fungi in air over the Atlantic Ocean. Mycologia 47: 34–50.

Peccia J and Hernandez M (2006) Incorporating polymerase chain reaction‐based identification, population characterization, and quantification of microorganisms into aerosol science: a review. Atmospheric Environment 40: 3941–3961.

Saint‐Jean S, Chelle M and Huber L (2004) Modelling water transfer by rain‐splash in a 3D canopy using Monte Carlo integration Ag. Forest Meteorology 121(3–4): 183–196.

Saint‐Jean S, Kerhornou B, Derbali F et al. (2008) Role of rain‐splash in the progress of Septoria leaf blotch within a winter wheat variety mixture. In: West JS and Burt PJ (eds) Applied Aspects of Aerobiology. Harpenden, UK: Rothamsted Research. 19 November 2008. Aspects of Applied Biology 89: 49–54.

Shiller JB, Lebas BSM, Horner M , Pearson MN and Clover GRG (2010) Sensitive detection of viruses in pollen using conventional and real‐time reverse transcription‐polymerase chain reaction. Journal of Phytopathology 158(11–12): 758–763.

Smith MJ (2008) The Biology and Molecular Biology of Polymyxa Species and their Interactions with Plants and Viruses. PhD thesis, University of Warwick.

Suzuki S, Oshima K, Kakizawa S et al. (2006) Interactions between a membrane protein of a pathogen and insect microfilament complex determines insect vector specificity. Proceedings of the National Academy of Sciences of the USA 103(11): 4252–4257.

Weller SA, Stead DE and Young JPW (2006) Recurrent outbreaks of root mat in cucumber and tomato are associated with a monomorphic, cucumopine, Ri‐plasmid harboured by various Alphaproteobacteria. FEMS Microbiology Letters 258(1): 136–143.

West JS (2012) Aerobiology and air sampling in plant pathology. Alergologia Immunologia 9: 80–81.

West JS, Heard S, Canning GGM, Fraaije BA and Hammond‐Kosack K (2013) New developments in identification and quantification of airborne inoculums. Acta Phytopathologica Sinica 43(suppl.): 16. International Congress of Plant Pathology 2013 abstract O01.002.

West JS, Kharbanda PD, Barbetti MJ and Fitt BDL (2001) Epidemiology and management of Leptosphaeria maculans (phoma stem canker) on oilseed rape in Australia, Canada and Europe. Plant Pathology 50: 10–27.

Yang X, Madden LV, Reichard DL, Fox RD and Ellis MA (1991b) Motion analysis of drop impaction on a strawberry surface. Agricultural and Forest Meteorology 5: 67–92.

Yang XS, Madden LV and Brazee RD (1991a) Application of the diffusion equation for modeling splash dispersal of point‐source pathogens. New Phytology 118(2): 295–301.

Zappia RE, Hüberli D, Hardy GE and Bayliss KL (2013) Biosecurity implications of plant pathogens in irrigation water. Acta Phytopathologica Sinica 43(suppl.): 83. International Congress of Plant Pathology 2013 abstract O04.011.

Further Reading

Agrios GN (2005) Plant Pathology, 5th edn., p. 952. Amsterdam: Elsevier.

Web Links

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
West, Jonathan S(Feb 2014) Plant Pathogen Dispersal. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0021272]