Emerging Themes and Approaches in Plant Virus Epidemiology.

Plant diseases caused by viruses share many common features with those caused by other pathogen taxa in terms of the host-pathogen interaction, but there are also distinctive features in epidemiology, most apparent where transmission is by vectors. Consequently, the host-virus-vector-environment interaction presents a continuing challenge in attempts to understand and predict the course of plant virus epidemics. Theoretical concepts, based on the underlying biology, can be expressed in mathematical models and tested through quantitative assessments of epidemics in the field; this remains a goal in understanding why plant virus epidemics occur and how they can be controlled.

Pest categorisation of spp. (non-EU).

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of spp. (non-EU), a well-defined and distinguishable group of fungal plant pathogens of the family Pucciniaceae affecting woody species. Many different species are recognised, of which at least 14 species are considered not to be native in the European Union.

Pest categorisation of .

Following a request from the European Commission, the EFSA Plant Health (PLH) Panel performed a pest categorisation of , a well-defined and distinguishable fungus of the family Xylariaceae native to North America. The species was moved from the genus to the genus following a revision of the genus. The former species name is used in the Council Directive 2000/29/EC.

Network epidemiology and plant trade networks.

Models of epidemics in complex networks are improving our predictive understanding of infectious disease outbreaks. Nonetheless, applying network theory to plant pathology is still a challenge. This overview summarizes some key developments in network epidemiology that are likely to facilitate its application in the study and management of plant diseases.

Integrating natural and social science perspectives on plant disease risk, management and policy formulation.

Plant diseases threaten both food security and the botanical diversity of natural ecosystems. Substantial research effort is focused on pathogen detection and control, with detailed risk management available for many plant diseases. Risk can be assessed using analytical techniques that account for disease pressure both spatially and temporally.

Disease spread in small-size directed networks: epidemic threshold, correlation between links to and from nodes, and clustering.

Network epidemiology has mainly focused on large-scale complex networks. It is unclear whether findings of these investigations also apply to networks of small size. This knowledge gap is of relevance for many biological applications, including meta-communities, plant-pollinator interactions and the spread of the oomycete pathogen Phytophthora ramorum in networks of plant nurseries.

Modelling disease spread and control in networks: implications for plant sciences.

Networks are ubiquitous in natural, technological and social systems. They are of increasing relevance for improved understanding and control of infectious diseases of plants, animals and humans, given the interconnectedness of today's world. Recent modelling work on disease development in complex networks shows: the relative rapidity of pathogen spread in scale-free compared with random networks, unless there is high local clustering; the theoretical absence of an epidemic threshold in scale-free networks of infinite size, which implies that diseases with low infection rates can spread in them, but the emergence of a threshold when realistic features are added to networks (e.