The pathozone is the region of soil surrounding a host target within which a pathogen must lie in order to be able to infect the host. It can be quantified using placement experiments, in which discrete units of inoculum are placed at different distances in soil from the host. The proportion of infected hosts at each distance in then used as an estimator of the probability of infection.
The epidemiological challenges are to quantify:
- the spatial and temporal dynamics of the pathozone;
- the effect of disease control measures as well as soil type and other environmental variables on pathozone dynamics;
- the relationships between colony dynamics and pathozone behaviour;
- how it can be used to predict epidemic behaviour at the large (patch to field) scale.
Most of our work has been focused on the pathozone for Rhizoctonia solani, and the way that this changes when a biological control agent (Trichoderma viride) or a fungicide is added in different soil types. Other work has been directed towards the wheat take-all fungus, Gaeumannomyces graminis, as well as the oomycetes, Pythium ultimum (a widely occurring damping-off disease) and Polymyxa betae (the vector of rhizomania disease of sugar beet) and the parasitic Nematode, Meloidogyne incognita.