Much effort has been made in the field of plant disease epidemiology to link disease incidence and severity with short-term weather variables. However, few studies have been published on the effects of longer-term weather patterns or climate change on plant disease, despite an earlier presentation of a good case for this type of approach (Coakley, 1988). The Fusarium foot-rot disease complex of wheat provides an interesting opportunity for the study of the impacts of climate on both the severity of a disease of an herbaceous plant and the competition between the various pathogen species capable of causing foot-rot symptoms. This chapter outlines a recent study on the effects of climate, particularly air temperature, on Fusarium foot rot in UK cereals, with the aim of developing predictive models.

The disease

Fusarium foot rot of temperate cereals is a disease caused by several Fusarium or Fusarium-like species, each of which may infect stem bases individually or, in complex infections, involving two or more species. Fusarium foot rot in winter wheat is commonly caused in the UK by four species: Fusarium culmorum, Fusarium avenaceum, Microdochium nivale (formerly Fusarium nivale) and to a lesser extent F. graminearum (Parry et al., 1994). The foot-rot symptoms caused by the four species are indistinguishable (Fig. 2.1) and currently, the individual species present can only be reliably identified by the presence of perithecia in infected material or by isolations from diseased tissue pieces, using selective agar media and identification of emerging fungal colonies.