The group focuses on the integration of modelling with field and laboratory experiments to study population dynamics/epidemiology and evolutionary ecology of plants and their pests and pathogens. Current key areas include:
- sampling and control of invasive pathogens,
- evolutionary ecology of plant pests and pathogens and
- the sustainability of crop protection.
Key application areas are
- forest tree diseases such as sudden oak death (Phytophthora ramorum), acute oak decline (causal organism unknown) and ash dieback (Chalara fraxinea) and
- crop diseases such as Stem rust Ug99 (Puccinia graminis f. sp. tritici), a pathogen of wheat threatening recurrent famine in parts of Africa and Asia, cassava virus diseases in Africa and a range of fungal disease of wheat and oilseed rape in the UK.
As well as addressing fundamental research questions in these areas, the group has a strong track-record in collaborating with policy makers, regulatory agencies and industrial stakeholders.
The main focus of the group is the development and application of generic models to study the population dynamics and evolutionary ecology of plants and their pests and pathogens. Key areas are:
Sampling and control of invasive plant pathogens
Increases in global trade and travel have led to a vast increase in invasive plant disease epidemics with serious consequences for both nature conservation and food security. We are developing models and methods to advise on surveillance and control of such invaders.
The key question is how heterogeneous host distributions affect the epidemiology of plant pathogens (both crop and natural vegetation). This work has led to the development of spatially-explicit stochastic models to study the emergence of new pathogens and strains of endemic pathogens. We also develop sampling and monitoring methods as well as control methods for emerging pathogens. These methods are at this moment routinely used by the FERA led, DEFRA funded, national Sudden Oak Death control programme, and by USDA in the design of statewide sampling and mapping plans for diseases of citrus.
Specific examples of knowledge transfer:
- We have recently advised DEFRA’s Ash Dieback Science Policy Team on surveying strategies for Ash Dieback. This work also contributed to a report to DEFRA on strategic epidemiological modelling of Ash Dieback in collaboration with the University of Cambridge.
- We have provided survey methodologies to the US Department of Agriculture, Animal and Plant Health Inspection Service over the past five years. The methods are used as standard to conduct regular state-wide surveys in Florida and other US states for a range of invasive citrus pathogens.
Evolutionary ecology of plant pathogens
Any disease control method selects for pathogen strains less prone to the control. Environmental change will also select pathogen strains more suitable to the changed environment.
The key question here is how pathogen and host life-cycle components affect the evolution of plants and pathogens. Amongst other we have shown (i) the existence evolutionary bi-stability in pathogen transmission mode and the effects of environmental change on the balance between horizontal and vertical pathogen transmission, (ii) that the evolution of defence mechanisms reduce the likelihood of coexistence of plant species which is contrary to commonly accepted view that pathogens facilitate coexistence, and (iii) how environmental change affects the adaptation of pathogen life-cycle parameters.
For example, using the 160 year time-series from the broadbalk experiment we demonstrated that the historic jumps between two different transmission modes in a pathogen of wheat, Phaeosphaeria nodorum, could be interpreted as adaptation to environmental change.
Sustainable crop protection
The evolution of new pathogen strains that overcome existing disease control is a central threat to food security (for example, through fungicide resistance or host virulence). We are developing models and methods that minimise selection for new strains and improve the durability of disease control.
The key question is how epidemiological and population genetic processes interact in selection for pest and pathogen life-cycle characteristics. Amongst other things we have developed methods to quantify the consequences of crop resistance for the selection of virulent pathogen races. Similar approaches were used to study the effect of a range of resistance management strategies on the evolution of fungicide resistance. Findings from the work are now informing and influencing practical decision making, in liaison with the Chemicals Regulation Directorate (CRD) of the Health and Safety Executive (HSE), the Fungicide Resistance Action Group (FRAG), the Fungicide Resistance Action Committee (FRAC, representing the crop protection industry) and the European Plant Protection Organisation (EPPO).
Specific examples of knowledge transfer:
- We have been involved in the discussions within CRD and FRAG around the registration of seed treatments.
- We have recently been asked by the Grains Research Development Corporation (GRDC) of Australia to help develop a resistance management strategy for fungicide resistance in broad acre crops in Australia, a country where resistance has recently been confirmed for the first time.
Dennis te Beest
Key External Collaborators
Professor Chris Gilligan, Plant Science Department, Cambridge University.
Dr. Tim Gottwald, USDA, Fort Pierce.
Dr. Neil Paveley, ADAS High Mowthorpe.
Dr. Christian Lannou, INRA, Grignon, France.
Dr. Neil McRoberts, Plant Pathology University of California.
Professor Mike Shaw, Plant Pathology, University of Reading.