Agricultural biosecurity: threats to crop production Michael Jeger Division of Biology, Imperial College London Beijing workshop, 31 Oct 3 Nov 2010
Outline of presentation Crop production, origins and cultivation Biodiversity of plant pathogens Agricultural, natural and human contexts From field to global spread Case studies banana and cassava Invasive and emerging plant pathogens Relevance of pest risk assessments
Global production of eight major crops and estimated losses by crop and region (1988-90) Rosenzweig et al. (2001) Global Change & Human Health
Crop biogeography and origins of the major food crops rice, wheat, maize and potato, only rice is grown predominantly where it originated in SE Asia wheat originated in the Middle East maize originated in the Americas potato originated in the Andes Can be considered beneficial plant invasions
Introduced crops may carry plant pathogens with them or acquire pathogens as a consequence of new encounters in the new environment. Invasive plant pathogens occur over different time scales Evolutionary time Centuries/decades Within a cropping season
Contrasting features of traditional and modern methods of crop production. Feature Traditional Modern Fields Crop Species Cultivars Propagules Inorganic fertilizers Herbicides/Pesticides Rotations Traction Small, irregular Often inter-mixed Often inter-mixed Usually landraces Own-grown or produced locally Seldom used Seldom used Much use of bush fallow Mainly human/animal Large, regular Usually single Usually grown singly Usually specially bred Usually specially bred Usually purchased Seldom produced locally Used routinely Often used Limited use of fallow Mechanical
APSnet (2001)
Intensification and incidence of virus diseases For rice production, intensification of cultivation is based on the introduction of high yielding varieties, increased use of irrigation, fertilizers and pesticides, crop monoculture and mechanisation about 25 viruses shown to have direct economic impact may lead to epidemics requiring integrated management practices
Biodiversity of plant pathogens Photos: American Phytopathological Society, www.apsnet.org - Online Resources
Photo: William Fry, Cornell University Phytophthora species
Potato late blight (Phytophthora infestans) in Peru From Garrett et al. (2009) Ecological Applications
Geographical distribution of the Phytophthora infestans mating types From Smart & Fry (2001) Biological Invasions
Jarrah forest dieback due to Phytophthora cinnamomi from: http://www.cmis.csiro.au/rsm/casestudies/flyers/dieback/bluffdie2.jpg
Tyler B.M. et al. (2006) Science, 313: 1261 1266
Severe Canker on Citrus Fruits Secondary infection by fungal/bacterial organisms can occur
Characteristics of citrus canker in Florida Urban Miami in 1995 (introduced in 1992/93) continuing to expand During the course of the epidemic 1.56 million commercial trees 0.6 million residential trees potential $2 billion impact on Florida citrus industry
Citrus canker Existing regulatory policy on removing trees (~ 40 m from symptomatic tree) USDA ARS, University of Florida, State Regulatory Authorities determined ~ 600m (Jan 2000) (Gottwald et al., 2002) Conflicts/tensions with homeowners/legal challenge/expert testimony
Epidemiological scales of spread Field scale farmers Regional/national scale national economies Global scale natural and anthropogenic An interconnected world international trade
Long dispersal of tobacco blue mold (Peronospora tabacina) Blue mold advances in a wave from the southern most tobacco growing regions to the northern most each year in the eastern USA.
Dispersal of the wheat yellow rust pathogen, Puccinia striiformis f. sp. tritici, in China. Photo by Yue Jin, US Dept. of Agriculture Map from Brown & Hovmøller (2002) Science
J K M Brown and M S Hovmøller (2002) Science 297: 537 54
Plant movements in a globalized world passengers From: Hufnagel et al. (2005) PNAS (air) & Kaluza et al. (2010) Interface (sea)
Bananas; an endangered fruit 16/01/2003 London Fungal disease could finish off the banana within 10 years, with dire consequences for half a billion people in Africa and Asia for whom it is a staple, according to a French research scientist writing in the New Scientist journal Thursday.
APSnet (2001)
Inibap (1997)
APSnet (2001)
Extracts from New Vision, Uganda, April 28, 1989 CASSAVA IN WEST NILE HIT BY DISEASE Cassava, the second staple food crop in West Nile after millet, is becoming extinct in the region following a cassava mosaic virus epidemic which has befallen the region for nearly two years now.
Thresh and Cooter (2005) Plant Pathology 54: 587 614
Natural Resources Institute (1997)
University of Arizona (2003)
From Rodoni (2009) Virus Research Emerging plant diseases
Invasive plant diseases: key questions in relation to biosecurity What is the threat to national agriculture/environments? Is eradication of a pathogen feasible? What safeguards should be built into national Plant Health systems? Is global trade responsible for new and exotic plant pathogens? What will be the impact of global climate change? Can we predict the next problem? Is the pathogen that arrives or the one that follows the more important?
Emergence of new evolved strain (after Antia et al., 2003) crop
Methodology used by Latxague et al. (2007) for assessing the risk posed by agroterrorism in Europe.