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Julius Kühn-Institut (JKI)
Federal Research Institute
for Cultivated Plants

apl. Prof. Dr. Johannes Hallmann

Messeweg 11/12
38104 Braunschweig, Germany

Institute leaflet
Institute booklet

Epidemiology of pathogens

How do pathogens spread? Which population densities do they achieve and how do they damage our crops? Are there thresholds up to which pests can be tolerated, and if so, how can such damage thresholds be integrated as part of a sustainable and environmentally sound pest management system? The Institute for Epidemiology and Pathogen Diagnostics provides answers top this.

The term "epidemiology" describes how diseases develop and pathogens spread in cultivated crops. Epidemics are controlled by three main factors: the pathogenicity of the organism, the susceptibility of the plant and the prevailing environmental conditions. In addition to that, viruses also require specific vectors for their proliferation.

Only if the relevant factors fit together, a pathogen may develop and cause economic damage. The interactions between pathogen and host plant have a high dynamic range, since both partners are continually striving  for its advantages. Understanding the underlying mechanisms means to specifically use them in terms of improved plant health.

Crucial on the site of the pathogen is its multiplication potential, its mobility and aggressiveness or virulence. The latter is responsible whether the pathogens can overcome the defense mechanisms of the plant and multiply in it. Only when a compatible host-pathogen interaction exists, it may result in plant damage. Likewise, environmental factors, such as temperature and humidity, must be favorable for the pathogen.

The cultivation of new crops, changing crop rotation, minimum tillage, climatic changes and worldwide trade permanently cause changes in epidemiological processes and must be continuously scrutinized anew.

We analyze the diversity of pathogens, their distribution channels and the dynamics of their increase in the crop. Our results provide a basis to define damage thresholds and to develop effective and environmentally sound control measures. We examine the biology of pests and investigate the causes for compatible or incompatible host-pathogen interactions. The focus of our research also includes factors that are responsible for the transition of a pathogen from the latent to the pathogenic phase within a host plant. Our goal is to create a better understanding of the interrelationships between pathogens, their vectors and the host plant as basis to develop environmentally friendly control methods within a sustainable management of these pathogens.